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Organic Evolution in terms of the Implicate and Explicate Orders.

Part LXX

Diptera (midges, mosquitoes, flies) (II)

The evolutionary diversification in the Order Diptera revisited.

Origin and Evolution of the Order Diptera

Derivation of the many dipterous wing-venations from the venational prototype of the Order Diptera, and a full exposition of the functional wing-types of the Order. (Sequel-1)

After having, in the previous document, started with the thematic treatment of the functional wing-types and subtypes in the Order Diptera and their derivation from the order-prototype, we continue this in the present document.

Pseudo-feather-winged (itonidoid) type

( Figures 10a -- 12a)

Representatives of the type
Wings of the pseudo-feather-winged (itonidoid) type are characteristic for the extensive family of gall-midges-proper Itonididae  [ = Cecidomyiidae] and for the related family Heteropezidae. See next Figures.

Figure 10a :  Wing of male of  Mayetiola  destructor SAY.  (Cecidomyiidae).
(Part of drawing by CURRAN, 1934, in ROHDENDORF, 1964)

Figure 11a :  Cecidomyiidea, family Itonididae  [ = Cecidomyiidae].
From top to bottom :
115 -- Lasioptera ?  flexuosa WINN.
116 -- Cordylomyia  rudis WINN.     
117 -- Asphondylia  sarothamni LW.
118 -- Miastor  hastatus KIEFF.      
Interpretation of the wing-venation according to HENNIG.
(115-117 after HENNIG, 1954.  118 from HENNIG, 1954, after KIEFFER, 1913)

Figure 12a :  Basiala of wing of  Contarinia  tritici KIRBY.  ( Cecidomyiidae).  Schematic.
( From ROHDENDORF, 1946, after VENTURI, 1938 )

Size of wings
The absolute sizes of wings belonging to the pseudo-feather-winged (itonidoid) type are very small, they vary from 1 to 5 mm. As to the relative wing-size, the wing-length is about the same as the body-length or a little more. The surface-area and load of the wings is virtually not investigated.  I  [Rohdendorf] have received data only concerning two species of the genus  Contarinia :  The surface-area (as always, of both wings taken together) varies from 0.063 to 0.066 cm2 .  The load of the wings of these two investigated insects was equal to 0.011 gr/cm2.  The ratio of weight of wings and body-weight is not investigated.

Shape of the wings
Wings always moderately elongate, often short, 2-2.5, rarely 3 times longer than wide. The fore-margin moderately convex, often almost rectilinear. Hind-margin more convex. Apex small, little distinct. Anal lobe weakly expressed, in the form of a convex projection of the wing. Basiala, see Figure 12a above ,  little distinct, the proximal boundary of the anal lobe [which would then mark the distal boundary of the basiala] not sharply expressed. The alula is absent. Wing-scale only present as a germ. The wing-tip is often very obtuse.

Skeleton of the wing
How the insects hold their wings when not flying is little known to me [Rohdendorf]. The wing-venation is strongly reduced. In most cases virtually without a trace of costalization. The veins are rectilinear, thin, distributed over the whole wing-blade, widely separated from each other.
The costal vein runs up to the wing-tip but not beyond it. The hind-margin is, consequently, without a marginal vein (the assertion of the presence of the costal vein along the hind-margin of the wing in gall-midges, common in the literature, is certainly wrong ! ).
The subcostal vein is almost completely reduced.
Two simple  [ = unbranched] radial veins [or, as one might say, branches].
Medial veins present as three or one branch, sometimes totally absent. The two anterior branches are the weakest, forming the characteristic fork as seen in the fungivoroid wings. These veins are often reduced.
The posterior medial vein is always unified with the cubital vein as it were its branch. These veins are significantly more rarely reduced. The basal part of the medial vein is stronger. In the case of reduction of medial branches it often forms, as it were, the continuation of the cross-vein  rm  to the wing-base.
Cubital vein almost rectilinear, curved at its end.
Anal veins reduced.
The basiala is very peculiar and possesses two well-expressed convex elements and a central concave one. Sometimes at the end of the 'handle' of the radial vein we find the indication of a fragma in the form of a transverse projection or of some sort of [small] separating wall. The 'handle' [ = knob-like proximal end] of the radial vein is strongly broadened and firm. The chaetaria are present as clearly distinct plates-with-bristles on the upper surface of the basiala, [that is,] on the handles of the radial and second anal vein.  [ For the various structures of the basiala in general, see in Part II where we deal with the  functional interpretation and evolutionary evaluation of the features of the wings of the order Diptera,  especially the Figures 1a and 1b ].

Coverings of the wing
The whole wing-membrane is covered by many rather densely packed microtrichia which are very short (3-4 mu). Almost always there is a covering of many fairly long macrotrichia which cover the whole wing-blade fairly uniformly. The macrotrichia are arcuately curved, not particularly thin, spinelets, of which the length varies from 60 to 120 mu. Flat spinelets are absent. The hind-margin of the wing and the wing-scale with long macrotrichia.
The nerve system of the wing is not studied.

Functional characteristic
The way of life of these utterly small diptera is, in general terms, well known. The larvae of the great majority of the representatives of the family Itonididae live in the tissues of living plants. As a rule they are narrowly monophagous. Some forms are predators on the surface of plants, eating aphids and ticks. Some other species of the mentioned family, and also almost all species of the family Heteropezidae, live in the larval phase in rotting wood and under the bark of trees. The majority of the winged insects is aphagous with a relatively short life. The flight of the itonidids undoubtedly has a completely determined fairly important meaning in their life-activities, making it posssible for the monophagous insect to find its food plant. Other abilities for moving around are apparently of secondary significance.
In evaluating the flight features of these insects we must first of all take into account their minute or most minute sizes, which determine characteristic features in the development of this locomotory function. The low body-weight of the itonidids  ( The weight of two representatives of the genus  Contarinia  is known to be as low as 0.0007 grams) and the structure of their wings, clearly point to their flight apparatus to belong to the feather-winged type, namely to the peculiar pseudo-feather-winged subtype (pseudo-ptilo-pterygia) (ROHDENDORF, 1949). The pseudo-feather-wingedness of the gall-midges bears witness to special features of flight of these insects, which [flight] is not fast or particularly steerable. Passively being carried by air-currents probably is of great significance for the gall-midges. To this the low load bears witness and also all of the structure of their body (slender body, the long thin prehensile legs, and the development of hairs on many parts of the body and its appendages). It is certain that during flight the actual load exerted on the wings of the insect is still lower, because the projective surface-area of the whole body without the wings is sufficiently large and significantly changes the magnitude of the general load exerted on the insect as a result of dividing the load over other appendages of the body. Exact observations of the flight of these insects have not yet been made.

History and transformations of the type.
The available paleontological documents almost only clarify the upper Eocene fauna preserved in the Baltic amber which includes many species of the families Itonididae  [ = Cecidomyiidae] and Heteropezidae. To understand the ways of formation of the present wing-type this material has little to offer. It just indicates the close relationship obtaining between the eocene and recent forms. The transformation of the pseudo-feather-winged type in fact only consists of the presence of the different stages of reduction of the wing-venation which hardly allows to divide it into individual subtypes. First of all we must notice the richest venation [as compared with that of other members of the type] of the representatives of the groups Campylomyzinae and Porricondylini. These forms we can naturally consider to be the most primitive forms and the starting-points for the remaining forms. The chief mass of other gall-midges possesses a more reduced wing-venation (see Figure 11a, above ),  and here belongs the majority of the representatives of the family Itonididae. Finally, the species of the family Heteropezidae and some of the family Itonididae (Lasiopterini) have the most reduced wing-venation and form the extreme most specialized group of the itonidoid type.
The connections of this type with other types are clear. The pseudo-feather (itonidoid) wings originated from the  ancient lifting venationally-attenuated (fungivoroid) wing-type (previous document) ,  namely from its two subtypes, the pleciomimoid (previous document)  subtype and the lycorioid (previous document)  subtype (all described in Part VI and also in previous document  ( Part LXIX )). These processes of the formation of the type have a clearly regressive character and consist in the reduction of the wing-venation which looses the features of costalization, and which was significantly weakened, [consist further] in the development of a cover of macrotrichia, and, what is especially important, [consist in] the accompanying decrease of body-size. This latter process -- decrease of body-size -- was the decisive fact in the formation of the itonidoid type of wings, and at the same time [the decisive fact] in the regressive character of the evolution of these organs. As had already been said (Part VI), where we considered the pathways of evolution of the fungivoroid wings, a regressive character of changes in one or another single organ-system does not necessarily mean an overall regression of evolution of the group as a whole. This is especially clearly shown by the example of the evolution of the gall-midges, of which the flowering and development was determined by progressive changes in the organization of their developmental phases [larvae], namely the working-out of extra-intestinal digestion in their larvae, accompanied by various changes of the structure of their mouthparts, the refinement of metamorphosis, etc. At this background or framework of progressive changes, the regressive changes of the wings and flight form just a one-sided specialization of a single organ-system of which the function was changed in connection with changes in the living-conditions.

End of the exposition of the functional wing-type as it is present in (certain) representatives of the superfamily Cecidomyiidea.)

* * *

Ancient lifting many-veined (bibionoid) type

Next we present a description of this type as such. As one can see, it occurs not only in the superfamily Bibionidea, but also in other superfamilies (such as the Scatopsidea).  (Figures 1 -- 9 below)

Representatives of the type
Wings of the ancient lifting many-veined (bibionoid) type are possessed in the recent fauna by representatives of the families Bibionidae, Amasiidae, Axymyiidae, Scatopsidae, Synneuronidae, and Canthyloscelididae.

Size of the wings
The absolute size of the wings are variable. They vary from 2 to 10 mm. The relative size of the wings is such that their size is equal to that of the body or larger. The surface area and load of the wings are only known for one species of the family Bibionidae :  The surface area is equal to 0.119-0.218 cm2 .  The load is equal to 0.023-0.037 gr/cm2 .

Figure 1 :  Wings of recent representatives of the ancient lifting many-veined (bibionoid) type. From top to bottom :

(After ROHDENDORF, 1951)

[Here I assume that the names "Canthyloscelididae", "Hyperoscelididae", and "Corynoscelidae", signify one and the same single family, or at most three slightly different families. The family Synneuronidae is probably close to this complex. They all belong to the superfamily Scatopsidea.]

[Although the families Canthyloscelididae and Scatopsidae are closely related to each other (both belonging to the superfamily Scatopsidea), it is not clear to me why ROHDENDORF includes the wings of the Scatopsidae in the present functional wing-type. As we can see in Figure 2, below, veins in the wings of Scatopsidae (if the depicted species indeed represents the wing-venation of the family) are sparse in the sense that their density is (in most parts of the wing) quite low. This contrasts with the other members of the type.
We propose to remedy this as follows :
In principle a given typological boundary, separating two different types, may run right through a genealogical taxon, resulting in a part of this taxon (i.e. a subset of its representatives) belonging to one type, while the other part belongs to another, different, type. In the same way one and the same given type can be represented in several different not genealogically related taxa. But, for theoretical reasons, the discrepancy between the typological system, be it of functional wing-types, ecological types, or whatever, and the genealogical system (in the sense of HENNIG) may not be too great. The nature and variability of typological features is held within limits, limits as set by the immediate genealogical tree to which the species having certain given typological features belong. This means that a given type, such as a wing-type, cannot be, or is at least not expected to be, present in representatives of genealogically widely separated taxa. Even if -- to stick to wing-types -- the wings in such taxa formally look almost identical, they must be in some way different. These differences might be seated in the basiala, in the nature of the flight-muscles, or in some other allegedly minor structural features. On the other hand seemingly clearly different types might not be so different afterall, because they are possessed by, say, two, genealogically closely related taxa. The types can nevertheless be different, but the one type is, in such a case, apparently, the result of a more or less simple transformation of the other type which was also present in the common ancestor of the two taxa.
In this way, perhaps, we must approach the seemingly great typological difference between on the one hand the wings in the family Scatopsidae, and the wings in the complex Canthyloscelididae, Corynoscelidae, Synneuronidae on the other.
In order to make this more clear we will add some more Figures of wing-venation of relevant species and some comments, and integrate it with ROHDENDORF's text.
ROHDENDORF himself has also seen the great differences within the present type, that is the ancient lifting many-veined (bibionoid) wing-type. Therefore he, in a more or less integrated way, distinguishes four different subtypes (without naming them, but let us call them I, II, III, and IV) within this type, respectively containing the following families
] :

According to ROHDENDORF group II has descended from (ancestors of) group I, while the latter came from certain Fungivoroids.  Group IV has descended from (ancestors of) group III, while the latter came from some other Fungivoroids.

[With this scheme in mind it will be easier to follow ROHDENDORF's text from where we take it up again (We will say so when we do).
As a last remark concerning ROHDENDORF's description and exposition of the present wing-type we say that part of the name given to it by ROHDENDORF is not very significant, namely the part "many-veined" in ancient lifting many-veined (bibionoid) type.  Precisely as "many-veined" this type is not significantly contrasting with the representatives of the ancient lifting venationally attenuated (fungivoroid) type. We take it that in naming the present type -- the bibionoid wing-type -- ROHDENDORF has called it "many-veined" after the nature of its most primitive and oldest representative, and that is certainly Eoplecia : see Figure 9, below 

In HENNIG, 1954, we find a drawing of the wing-venation of yet another species of the genus  Amasia,  and this genus is included in the family Bibionidae by HENNIG :

Figure 1a :  Wing-venation of  Amasia  funebris MEIG.  ( Bibionidae [or : superfamily Bibionidea, family Amasiidae] ).
(After HENNIG, 1954)

[Some more Figures should be added here] :
In addition to the in Figure 1 (bottom image) depicted Eucorynoscelis  eximia BOH.  ( Canthyloscelididae) we give here the wings of two more genera, apparently closely related to  Eucorynoscelis :

Figure 1b :  Wing-venation of  Corynoscelis  eximia BOH.  ( Corynoscelidae).
[The species  eximia BOH. we have, as it seems, already encountered in Figure 1 (bottom image), there placed into the genus Eucorynoscelis. As can be seen, they differ with respect to M2. But this could be attributed to mere individual variation within one and the same species.]   (After DUDA, 1928, from HENNIG, 1954)

Figure 1c :  Wing-venation of  Synneuron  annulipes LUNDSTR.  ( Corynoscelidae [ or: superfamily Scatopsidea, family Synneuronidae] ).  In addition to the coalescence of the anterior medial vein with the Radial Sector we see here a coalescence, at one point only, of the Radial Sector and the Radius.
(After DUDA, 1928, from HENNIG, 1954)

It seems that in the complex Canthyloscelididae-Corynoscelidae-Synneuronidae there is a tendency to reduce the venation eventually leading to that of the family Scatopsidae. The next Figure depicts a wing of a representative of this family which is supposed to include wings of the present type.

Figure 2 :  Wing-venation of  Scatopse  fuscipes MEIG.  ( Scatopsidae).
(After HENNIG, 1954)

In addition to the wings of the Scatopsidae the transformational tendencies in the above mentioned complex (or perhaps some group already within the Scatopsidae) may also have led to the wings of the Cecidomyiidea  [ = Itonididea] :

Figure 2a :  Wing-venation of  Lestremia  cinerea MEIG.  ( Itonididae [or : superfamily Cecidomyiidea (=Itonididea), family Lestremiidae)].
(After HENNIG, 1954)

[After having added Figures and comments, we will now continue with ROHDENDORF's text, where he successively discusses the features of the ancient lifting many-veined (bibionoid) wing-type, to begin with the shape of such wings] :

Shape of the wing
Anterior margin very slightly but clearly convex, less often totally straight (in Scatopsidae). The apex of the wing [as apex] indistinct. Hind margin strongly convex, with a distinct anal lobe, generally projecting as a rounded rectangular outgrowth, less often weakly expressed (some Scatopsidae and Canthyloscelididae).
The wings are moderately elongate, generally 2-2.5 times longer than wide, less often shorter (some Scatopsidae).
The basiala usually distinct as a result of the presence of the sharp proximal boundary of the anal lobe and the humeral cross-vein. An alula is not developed, the posterior margin of the basiala is straight. There is a weakly developed wing-scale. See next three Figures.

Figure 3 :  Bibio  japonicus  DUDA.  ( Bibionomorpha-Bibionidae).  Wing-base, basiala.  Schematic.
Abbreviations as usual.  Ch = chaetarium (chaetarium radiale and chaetarium anale).
(After ROHDENDORF, 1946)

Figure 4 :  Basiala of wing of  Corynoscelis  exima BOH.  ( Corynoscelididae).  Schematic.
Abbreviations as in previous Figures :  from top to bottom : Costa (C), Subcosta (SC), Radius (R), Anterior Cubitus (CuA), and Posterior Cubitus (CuP).
(After ROHDENDORF, 1946 )

Figure 5 :  Basiala of wing of  Scatopse  notata MEIG.  ( Scatopsidae).  Schematic.
Abbreviations as in previous Figures.
(After ROHDENDORF, 1946 )

Skeleton of the wing
The resting position of the wings [still of the ancient lifting many-veined (bibionid) type] is such that they are held together along the body. Very characteristic is a sharply expressed costalization of the wing-venation, which is accomplished by the significant strengthening of the Costa, the Radius, and the base of the medial vein together with a weakening of all the other veins, and, finally, by the reduction of radial and medial branches, and the shift of the strengthened veins to the fore margin and to the wing-base (see especially Figure 2, above ).  Only in some, undoubtedly original, forms of this type costalization is weakly developed, as in Amasiidae, Axymyiidae, and Canthyloscelididae (see Figure 1, above ).
The number of radial veins usually is equal to only two. Only in the ancient relict groups a larger number of radial branches is preserved, namely three branches in Amasiidae and Canthyloscelididae and four in Axymyiidae
[According to me, however, things are as follows :  The venation, as it is shown in the top image of Figure 1, suggests that the vein ending up just after the wing-tip belongs to the radial system of veins (as if it were the third branch of the Radial Sector). But I think that this vein really is the first of the medial veins (M1) and that the radio-medial cross-vein, because of it having acquired a more or less longitudinal course, looks like the base of the last branch of the Radial Sector. If this is correct, then also the Axymyiidae -- judging from the wing depicted in Figure 1 (top image) -- have only three radial veins. However, another drawing of a wing of the same species (Axymyia  furcata McATEE) [but an idividual evidently coming from quite a different place] indicates that there is -- in that new specimen -- yet another, albeit short, radial branch, adding up to four radial veins after all. See next Figure].

Figure 6 :  Wing-venation of  Axymyia  furcata McATEE.  ( Axymyiidae).
(After CURRAN, 1934, from HENNIG, 1954)
[But still my interpretation of the above mentioned vein as being M1 (and not the last branch of the Radial Sector) still holds, and more so if the vestige drawn in Figure 1, top image  is really a vestige and not some accidental feature of the drawing. So if this drawing is correct (and also, of course, the other drawing), then the wing of  Axymyia  has two long branches of the Radial Sector and a short or vestigial third branch.]

Always three medial branches present. Cross-veins well expressed only in Amasiidae and Axymyiidae (r-m  and  mcu) and partly so in Canthyloscelididae (only  mcu) [the  r-m  cross-vein has disappeared as a result of the coalescence of the last radial vein and the first medial vein (see Figure 1, bottom image )]
In the majority of forms of the main families Bibionidae and Scatopsidae the cross-veins are, in connection with the development of costalization, strongly modified, being placed differently, or even having been disappeared completely. As a rule the basiala lacks a phragma. Only in the Canthyloscelididae there is developed a peculiar phragma which connects the bases of the radial and cubital veins, by which the wings of these insects are clearly distinguished from the other representatives of the type (see Figure 4, above and compare it with the Figures 3 and 5). There are, in the basiala, large and dense, well expressed chaetaria at the base of the radial and second anal vein.

Coverings of the wing
The wings of this type are covered with diverse spinelets. The representatives of the Bibionidae, Amasiidae, and Axymyiidae, on the whole wing-membran carry a dense covering of large microtrichia which by their large size are distinguished from the microtrichia of all other Diptera. The absence of macrotrichia on the wing-membrane of these forms was for me the basis to presuppose (ROHDENDORF, 1946) the original [primitive, initial] nature of these structures, that is, their not yet having differentiated into micro- and macrotrichia. The [wings of the representatives of the] Canthyloscelididae and Synneuronidae [the latter belonging to the superfamily Scatopsidea] already possess both forms of spinelets :  there are many small microtrichia, among which are strewn a few larger [ones :] macrotrichia. In Scatopsidae we see only a few true microtrichia. On the veins [in contrast to the wing-membrane] macrotrichia are present almost in all groups. Scales are absent. The posterior wing-margin with elongate macrotrichia. The 'germ' of the wing-scale with long spinelets. Nerve system and sensoria of the wing not investigated.

Functional characteristics
The way of life of the insects possessing bibionoid wings is more or less known. The larvae of Bibionidae and Scatopsidae live in rotting substances, in soil or in dung. The winged insects fly toilsome, but often quickly assume flight, visiting flowering plants. The way of life of Amasiidae and Axymyiidae is very little known :  It is said that a European species of the genus  Amasia (A. funebris MEIG.), while having wings, cannot fly. The flight of Canthyloscelididae and Synneuronidae is totally unknown.
There are no precise data about flight (wing-beat frequency, speed, etc.).

[Before giving ROHDENDORF's exposition of the history of the present wing-type and its subdivision into four subtypes (mentioned ABOVE ), we include here parts of RODENDORF's 1946 discussions of the fossil families Paraxymyiidae, Protobibionidae, and Protoscatopsidae, especially where he discusses the question asking to which recent families (such as Axymyiidae, Bibionidae, Scatopsidae) they are closest. We include these discussions because they not only teach us something about the mentioned fossil families (which are afterall often based on single poorly preserved fossils) but also about the recent families themselves, especially how to interpret the venation of their wings. In addition we shall add Figures and comments.]

Family Paraxymyiidae  (Jurassic).

Based on  Paraxymyia  quadriradialis ROHD. :

Figure 6a :  Wing-venation of  Paraxymyia  quadriradialis ROHD.  ( Paraxymyiidae). Jurassic.  Interpretation of wing-venation according to HENNIG.  Length of wing 2.25 mm.
(After ROHDENDORF, 1946, from HENNIG, 1954)

Sc [subcosta] moderately short, thin, but clear. It ends up in C [costa]. Rs [radial sector] branches off from R [radius] with a sharp angle and consists of three strong branches that end up in C. The cross-vein  r-m  lies in the middle of the wing between the two branches that branch off from the trunk of Rs.  M [media] weak, having three branches. The common trunk of the medial system of veins is reduced, it is visible [in the fossil] in the form of a weak trace lying along the large basal cell. Cu [cubitus] thin. Anal veins not visible [in the fossil]. The wing is fairly broad.
The described group is idiosyncratic and possesses very primitive features, such as the presence of a radial sector with three branches, all of them strongly expressed and well-developed, as well as some, undoubtedly, features expressing specialization, such as the reduction of the common medial trunk, the weakly expressed Sc, the stronger development (thickening) of the veins of R and Rs together with the weakening of M and Cu.
What then are the relationships of the Paraxymyiidae with the other [nematocerous] Oligoneura? The most characteristic feature of specialization of the wing of this group consists in the reduction of the basal part of the medial trunk which also can be observed in the recent families Mycetobiidae (for  Mycetobia  pallipes MEIG. see HERE ),  Macroceratidae (for  Macrocera  lutea MEIG. see HERE ),  Ceroplatidae (for  Zelmira  fasciata MEIG. see HERE ),  Ditomyiidae (for  Ditomyia  fasciata MEIG. see HERE ),  Diadocidiidae (for  Diadocidia  ferruginea MEIG. see HERE ),  Axymyiidae (for  Axymyia  furcata McATEE. see HERE ) [here the medial trunk is present, but, I assume, weakly so],  Pachyneuridae (for  Pachyneura  fasciata ZETT. see HERE ) [here the medial trunk is weak],  and some others. Another important feature of the structure of the wing in Paraxymyiidae consists in the position of the branches of the Radial Sector, of which the first [that is, the most proximal] one branches off from the common trunk [of Rs] significantly proximally from the cross-vein  r-m.  This latter cross-vein thus lies between the two anterior branches of Rs [that is, lies on that level].
Such a positioning of the anterior branch of Rs is, among Nematocera, observed in only a few families, such as in Axymyiidae (for  Axymyia  furcata McATEE. see HERE ),  Phryneidae  [ = Rhyphidae] (for  Phryne  fuscipennis MACQ. see HERE ),  and for a part [that is : approximately or almost] in Mycetobiidae (for  Mycetobia  pallipes MEIG. see HERE )  and  Pachyneuridae (for  Pachyneura  fasciata ZETT. see HERE ).  This process of specialization of the wing-venation is, in the mentioned families, apparently already a more or less final stage :  At first there takes place the reduction of branches of the Radial Sector. In Mycetobiidae (for  Mycetobia  pallipes MEIG. see HERE )  and  Phryneidae  [ = Rhyphidae] (for  Phryne  fuscipennis MACQ. see HERE )  the second branch [that is, the distal one of the two anterior branches of Rs] has completely disappeared, while in Axymyiidae (for  Axymyia  furcata McATEE. see HERE )  and  Pachyneuridae (for  Pachyneura  fasciata ZETT. see HERE )  the two branches [originally branching off from the common trunk of the Radial Sector] have partly coalesced to form a single forked vein.
Fossils belonging to the upper Liassic group of Nematocera, especially the Protorrhyphidae  (for  Protorhyphus  stigmaticus HANDL. see HERE )  and the Eopleciidae (see Figure 9, below ), show, with respect to the structure of the radial system, a great similarity with the Paraxymyiidae [see Figure 6a, above ].  Especially remarkable is the fact that the branching pattern of the Radial Sector as it is present in all mentioned Nematocerous families is common to that in the Brachycera-Orthorrapha and even in Brachycera-Cyclorrapha :  In all these diptera the cross-vein  r-m  lies distally from the branching-off point of the first branch of the Radial Sector. See, for example the wing of  Rhagio  scolopaceus LW.  (Rhagionidae) (top image) and of  Erinna  atra MEIG.  (Erinnidae) (bottom image), both belonging to the Brachycera-Orthorrapha, HERE .
On the other hand, the high degree of specialization of the wing-venation -- reductions in the medial system, weakening of subcosta -- make it impossible to see the Paraxymyiidae as the ancestors of whatever recent group coming close to them in regard of the branching structure of the Radial Sector. The Axymyiidae, as well as the Paraxymyiidae, originated from ancestors which were close to the Liassic Eopleciidae. The Paraxymyiidae acquired a series of features of high specialization (here : features of reduction) while at the same time having preserved some primitive features.

Family Protobibionidae  (Jurassic)

Based on  Protobibio  jurassicus ROHD. :

Figure 6b :  Wing-venation (as far as preserved in the fossil) of  Protobibio  jurassicus ROHD.  ( Protobibionidae). Jurassic.  Length of wing 1.5 mm.
(After ROHDENDORF, 1946, from HENNIG, 1954)

Sc [subcosta] well developed, a little shorter than half the wing. It ends up at C.  Rs [radial sector] splits into two branches of which the longer (the posterior) branch reaches the wing-tip, while the short (the anterior) one ends up into R [radius] already quite a distance from the latter's end-point.The cross-vein  r-m  lies obliquely, and is long. M [media] and Cu [cubitus] weak. Because of bad preservation their structure is not clear. There is a transverse  mcu.  C, R, and Rs, strong, significantly thicker and darker than M and Cu. The wing is elongate, almost 3 times as long as wide.
The family Protobibionidae, described on the basis of a single genus, is very interesting :  In itself it connects purely fungivoroid characters with those of the specialized wings of the recent family Bibionidae :

Figure 6c :  Wing-venation  Bibio  marci L.  ( Bibionidae).  Length of wing about 8.5 mm.  (After HENNIG, 1954)

The original nature of the branching-off of  Rs  from  R  places the genus  Protobibio  close to the families Allactoneuridae [recent] (see for  Allactoneura  nigrifemur ENDERL. HERE  and Pleciofungivoridae [fossil] (see for  Pleciofungivora  major ROHD. HERE ).
On the other hand, the considerable length and oblique position of  r-m,  the significant thickening of the veins C, R, and Rs, brings the Protobibionidae close to the family Bibionidae, especially to the genus  Philia (=Dilophus). The characters by which the Protobibionidae differ from the recent Bibionidae consist in the presence of the anterior, albeit short, branch of the Radial Sector, the stronger, but short, Subcosta, the different shape of the basal parts of M and Cu, and the presence of a true  mcu.  Some of these characters are clearly more progressive in comparison with Bibionidae (such, for instance, the shortened Sc). They do not make possible to see the Protobibionidae as direct ancestors of the Bibionidae. But it is evident that the Protobibionidae came from ancestors of Bibionidae not long before [the origin of Bibionidae] and should be placed in the direct proximity to that [phylogenetic] trunk.

Family Protoscatopsidae  (Jurassic)

Based on  Protoscatopse  jurassica ROHD. :

Figure 6d :  Wing-venation (as far as preserved in the fossil) of  Protoscatopse  jurassica ROHD.  ( Protoscatopsidae). Jurassic.  Length of wing 2.0 mm.
Identification of veins according to HENNIG.  The latter assesses the first vein after the Costa as subcosta, which might be problematic because of the considerable thickness of this vein in the fossil wing. ROHDENDORF assesses it as Radius, which is probably better despite the Radial Sector then being very peculiar.
(After ROHDENDORF, 1946, from HENNIG, 1954)

The venation of the wing of  Protoscatopse  is strongly contracted and shifted toward the anterior wing-margin. A large part of the wing is without veins, it is membranous. Sc is absent. R almost straight. Rs with three branches. The Costa [C] runs a little past the end of the last branch of Rs. It does not reach the wing-tip. M delicate and thin. It has two branches. Cu almost straight. It is strong only up to the middle of the wing, and continues in the form of a fold. The wing is fairly narrow.
This newly described form is closest to the representatives of the recent family Scatopsidae, but differs from it by a series of clearly more primitive features. See Figure 2 which we reproduce here :

Figure 2 :  Wing-venation of  Scatopse  fuscipes MEIG.  ( Scatopsidae).
(After HENNIG, 1954)

Such primitive features are :  the presence of branches of the Radial Sector (developed two short anterior branches) lying in the cell between R and the main trunk of Rs. They demonstrate the secondary reduced condition of the venation of the system Rs in recent Scatopsidae. Then we have -- still in  Protoscatopse -- the nature of the coalescence of M with Rs (these veins are here positioned idiosyncratically, being apparently coalesced along a certain distance). The point of branching-off of M from the common trunk M + Rs lies markedly more distally than the R-Rs fork, and lets us remember the wing-venation in representatives of the family Corynoscelidae [ROHDENDORF writes : Corynoscelididae], see Figure 1b (and 1c), above .
These features of the wing-venation of the described Jurassic form (Protoscatopse) allow us to come up with serious corrections as regards the existing interpretation of the wing-venation of recent Scatopsidae on the one hand, and clarify the mutual genetic connections of these groups on the other. Until now [1946] (Duda, 1928) the wing-venation in Scatopsidae is compared with that in true Oligoneura, namely with that in Lycoriidae  [ = Sciaridae], and therefore it was held that Rs in its basal part has been transformed into a transverse vein and that the real radio-medial cross-vein (r-m) [ta in the next Figure] became integrated with the system of the straight strong vein M-Rs. See next Figure.

Figure 6e :  Wing-venation of  Lycoria  bicolor MEIG.  ( Lycoriidae). Compare with  Scatopse  fuscipes MEIG.  ( Scatopsidae), Figure 2, above .
(After HENNIG, 1954)

The position of the veins in Corynoscelididae did not fit into this system, and therefore it was held that this group was an aberrant [phylogenetic] branch [See Figure 1c, above]. The clear relict- and very ancient nature of the Corynoscelididae was not taken into account by the majority of authors who ignored the very interesting and instructive wing-venation of these rare insects.
In comparing the wing-venation in Scatopsidae, Corynoscelididae, and the new Jurassic form [Protoscatopse) we directly see the remarkable similarity in the branching of the veins  Rs  and  M  between Corynoscelididae and Protoscatopsidae :  This similarity consists in the coalescence of the trunks of  Rs  and  M1+2,  precisely as in Ceroplatidae, see next Figure :

Figure 6f :  Wing-venation of  Zelmira  fasciata MEIG.
( Ceroplatidae-Macroceridae (=Zelmiridae)).  (After HENNIG, 1954)

and [precisely as] in other related groups. Compare Corynoscelididae Figure 1c, above with Protoscatopsidae Figure 6d, above .  Together with all this, the general nature of the specialization of the wing-venation, that is, its shift to the fore-margin and its strengthening there -- especially the mutual approach of the trunks R and M+Rs in Protoscatopsidae and Scatopsidae :  Compare Protoscatopsidae Figure 6d, above  with  Scatopsidae Figure 2, above  -- cleary demonstrates that the base of Rs, that is the Radial Sector's branching off from R, has been disappeared in Scatopsidae, and that the so-called "base of Rs" is in Scatopsidae no more than the shifted proximal anterior branch Rs-Rs1 .
Now it is the right place to investigate the question whether the described Jurassic group [Protoscatopsidae] is a direct ancestor of recent Scatopsidae and Corynoscelididae. Right from the beginning we must, answer this question, with a definite "no" with respect to the Corynoscelididae. This latter group carries a series of most primitive structural features, forbidding to see it as the descendant of the already highly specialized Protoscatopsidae. Such a primitive feature of the Corynoscelididae is the weak mechanical specialization of their wings. The family Corynoscelididae is undoubtedly a very ancient -- relict -- group, which branched off from the common trunk of "scatopsoid" forms much earlier than the Protoscatopsidae.
Something totally different we see in the relationships between Scatopsidae and Protoscatopsidae. The absence of any trace of a Subcosta can be accounted a specialization of Protoscatopsidae as compared with the recent Scatopsidae. All of the rest of the venation as described above lets me reckon this Jurassic group to be very close to the first original forms of the recent Scatopsidae.

* * *

After having clarified the position of Corynoscelididae and, especially Scatopsidae, we can now continue with the exposition of the  Ancient lifting many-veined (bibionoid) wing-type,  as described by ROHDENDORF, 1951. Already given was :

Now we continue with  The history of the type and its transformations.  These transformations of the type during its history have resulted in the formation of subtypes. These subtypes are, as has been said earlier, only more or less implicitly exposed in ROHDENDORF's text. In order to follow this text properly we should have in mind the explicit system of the four subtypes I, II, III, and IV, as established  ABOVE .

The history of the type and its transformations
There exist fairly many paleontological documents concerning the history of the ancient lifting many-veined (bibionoid) wing-type. See next Figure.

Figure 7 :  Wings of fossil representatives of the ancient lifting many-veined (bibionoid) type.  From top to bottom :

(After ROHDENDORF,1946, from ROHDENDORF, 1951)

[As can be seen in  Mesopleciella  (top image in Figure above) the present type is hard to distinguish from the ancient lifting venationally-attenuated (fungivoroid) wing-type in which are included -- among others -- the wings of  Hesperinus] :

Figure 8 :  Wing-venation of  Hesperinus  imbecillus Lw.  ( Hesperinidae, Bibionidea). (After HENNIG, 1954)

[Compare this venation with that of Amasia funebris MEIG., HERE, which wings are supposed to belong to the present type.]

From the Jurassic fauna of Karatau are known representatives of the families Protopleciidae (3 genera, see Figure 7, top image ),  Eopleciidae (one genus)
[At least until 1964 Eopleciidae have not been found in Karatau (middle or upper Jurassic). The only representative of this family is Eoplecia  primitiva HANDL., found in the upper Liassic -- the Liassic is the oldest subdivision of the Jurassic -- of Mecklenburg (Germany, now Poland) and described by HANDLIRSCH] :

Figure 9 :  Wing-venation of  Eoplecia  primitiva HANDL.  Upper Liassic of Mecklenburg.
[It clearly belongs to the present wing-type.]
(After HANDLIRSCH, 1938,  from HENNIG, 1954)

and Paraxymyiidae (one genus, see Figure 7, second image ),  which possessed wings that let them be close to later Caenozoic and recent Amasiidae and Axymyiidae. In the same period (Jurassic) in this fauna (Karatau) there existed representatives of the other group of the type, namely species of the families Protobibionidae, see Figure 7, third image ,  and Protoscatopsidae, see Figure 7, bottom image ,  which already had specialized wings, that let them connect to the Caenozoic Bibionidae and Scatopsidae.
The Teriary fauna contained many species of the families Amasiidae, Bibionidae, and a few Scatopsidae. All Tertiary forms completely fall within the confines of generic characters of the recent representatives of the mentioned families. Considering the transformations that took place in the structure of the wings of the fossil representatives of the type, basing ourselves principally on the Mesozoic forms, we can note the following. Already in Jurassic times we see a great difference obtaining between the groups Protopleciidae + Eopleciidae + Paraxymyiidae and the Protobibionidae and Protoscatopsidae, corresponding with those differences, which are present in the recent fauna between the families Amasiidae + Axymyiidae on the one hand, and the Bibionidae and Scatopsidae on the other, and which must be interpreted as a secondary grouping of the bibionoid wings, that is as subtypes (see below). The essence of the changes within each of these subtypes boils down to the enhancement of costalization, which in the Jurassic forms was weaker expressed :  We see this in the fact of the existence of (1) a 'superfluous' forth radial branch in Eopleciidae, see Figure 9, above, and (2) a different position of the basal part of the medial vein, the presence of a third radial branch and of the cross-vein  mcu  in Protobibionidae, see Figure 7, third image, and (3) a large number of radial veins in Protoscatopsidae, see Figure 7, bottom image .  Another characteristic feature of the Jurassic forms is their small absolute size. It can confidently be held that the evolution leading from Protopleciidae to Amasiidae, as well as that leading from Protobibionidae to Bibionidae, went into the direction of increased size of the wings. Something different, apparently, can be seen in the development of Protoscatopsidae + Scatopsidae, the [body] size of which did not increase, but, apparently, decreased. The undoubtedly genealogically related groups Protopleciidae + Amasiidae and Protobibionidae + Bibionidae nevertheless show great differences in the directions of the evolutionary transformations of their wings, consising in the development of regressive processes in the first group and progressive processes in the second.
Indeed, the absence of large changes in wing-structure in Protopleciidae + Amasiidae, which only consists in some reductions of veins and the increase of absolute size, together with the observed reduction of the very flight-function, forces us to evaluate this [evolutionary] direction as being regressive.
Totally different things have taken place in the evolution of the trunk Protobibionidae-Bibionidae, in which the wings acquired important mechanical improvements, and the flight-function had a serious biological significance. This path of transformation of the type [that is, the ancient lifting many-veined (bibionoid) wing-type] can legitimately be called progressive.
In considering the evolutionary changes of the trunk Protoscatopsidae + Scatopsidae we must conclude that they are not regressive. But, the apparent diminution of size, the simplification of the form of the wing, the developing of an excessive costalization, bordering to a reduction of the venation, the idiosyncrasy of flight, which does not, apparently, exhibit especially high parameters of speed and steerability, do not let us evaluate this evolutionary path as being especially progressive either. The development of this subtype was a consequence of processes connected with the general direction of the evolution of the scatopsids (minute diptera with predatory larvae, the probable presence of aphagia  [= not taking food] of the winged phase, and a flight exhibiting a high wing-beat frequency).
The features of the evolutionary transformations of the wings in the families Canthyloscelididae and Synneuronidae are still totally unclear.

The above described heterogeneity among the representatives of the bibionoid wing-type evidently bears witness to the presence of secondary groupings, subtypes.
The first most primitive subtype is represented by the forms of wings in the recent Amasiidae, Axymyiidae, the fossil Eopleciidae, Protopleciidae, and Paraxymyiidae. This subtype distinguishes itself by weakly developed costalization in the wings, their large size, the presence of dense strong microtrichia on the wing-membrane. Flight in these insects is apparently slow and heavy :  some non-flying species are known.
The second subtype is characteristic of the representatives of the families Bibionidae and Protobibionidae. Costalization is well expressed by the thickening and strengthening of the anterior veins. As in the previous subtype, strong and dense microtrichia are well developed. As regards the other features this subtype is close to the first one. Undoubtedly it is its derivative.
The third subtype sharply distinguishes itself from the two previous ones. It is characteristic of the rare relict forms of the family Canthyloscelididae [As has been said above, the "families" Canthyloscelididae, Corynoscelidae, Corynoscelididae, Synneurontidae [Synneuronidae], and Hyperoscelididae, apparently belong to a single group, which might be called "Corynoscelidae" or "Corynoscelididae".]. The most typical features of this subtype are :  the development of a phragma in the basiala, see Figure 4, above ,  a rudiment [or beginnings] of the anal lobe, absence of costalization (see, for example, Figure 1b, above ),  lengthening of the wing, and the development of micro- and macrotrichia.
This subtype is undoubtedly the source of the next and most specialized subtype of wings, that is developed in the representatives of the family Scatopsidae. This subtype distinguishes itself by an extreme development of costalization, complexification of the structure of the basiala, see Figure 5, above ,  a strong development of the anal lobe (see Figure 2, above ),  shortening of the wing, and the presence of only short microtrichia.

The origin of the type [the type as a whole] of the ancient lifting many-veined (bibionoid) wings is more or less clear. On the one hand this type branched off from first forms of the ancient lifting venationally-attenuated (fungivoroid) type, which had worked out a distinct basiala and having reduced the venation, and in this way giving rise to the pleciofungivoroid subtype together with the first subtype of bibionoid wings (Protopleciidae + Amasiidae). On the other hand, the wing-subtype in the representatives of the family Canthyloscelididae is a derivative of one or another significantly more specialized form of wings, most probably of still unknown representatives of the fungivoroid type that had refined the basiala. This dual path of formation of the bibionoid type apparently precisely expresses the actual history and is, moreover, confirmed by the features of the [taxonomic] system of these insects :  Bibionidea and Scatopsidea are undoubtedly way out distinct superfamilies.
(End of the exposition of the bibionoid wing-type).

* * *

In the next document we will treat the Bibionomorpha in terms of  venational derivational lines and morphoklines  emphasizing their possible polyphyletic noëtic evolution (in contrast to their possible monophyletic evolution as discussed earlier (Parts XXVIII and XXVIII-A)). And in further documents to come we will continue with the exposition of still more functional wing-types, namely those of the rest of the Order Diptera, that is, mainly from the suborders Brachycera-orthorrapha and Brachycera-cyclorrapha (which we had not yet done in earlier documents).

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