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Organic Evolution in terms of the Implicate and Explicate Orders.

Part LXXIIIa

Diptera (midges, mosquitoes, flies) (Va)

The evolutionary diversification in the Order Diptera revisited.

Derivational Lines, Morphoklines and Polyphyletic evolution of empidoid wings

First (and only) derivational line :

( This line starts with some precursors (rhagionids and omphralids) of the empidoid wings)

As always, a "derivational line" orders venations of a series of existing [or having existed] species. It does not represent the actual phylogeny of those species, but indicates what kind of venational transformations might have taken place in the Implicate Order in the many parallel lines (morphoklines) (see below) each resulting in the venation of one of the species of the derivational line.

(for its position in the diagrams of morphoklines, see 1st diagram below)

Rhagio  scolopaceus,  Rhagionidae.    
Subcosta (SC) well developed. Radial Sector (RS) 3-branched. R3 absent. Discoidal cell present.
The cross-vein ta [= r-m] present in its original condition. M1, M2, M3, and M4 present.  tb1 [= base of M4] present.  tb2 [= m-cu] present. CuA [labelled as  cu1b  in the Figure] and 1A [in the Figure labelled as 1a] present, separately reaching wing-margin.

(for its position in the diagrams of morphoklines, see 1st diagram below)

Spaniopsis  clelandi,  Rhagionidae.    
Radial Sector (RS) still 3-branched. R3 absent.
M1, M2, and M4 present. M3 in the process of reduction.  tb1 [= base of M4] suppressed.  tb2 [= m-cu] present. CuA and 1A with a short commom stalk.

(for its position in the diagrams of morphoklines, see 1st diagram below)

Omphrale  fenestralis,  Omphralidae.    
Radial Sector (RS) still 3-branched. R3 absent.
M1 and M4 present, M2 and M3 absent.  tb1 [= base of M4] suppressed.  tb2 [= m-cu] present. CuA and 1A with a longer [than in Spaniopsis] commom stalk, reaching wing-margin.

The wing-venation of  Omphrale, although perfectly derivable from that of  Spaniopsis, is a side-line, i.e. it is not a direct link between  Spaniopsis and the rest of this derivational line. Its specialization consists in freeing the posterior wing-margin of veins, a process not continued in the rest of the line.

(for its position in the diagrams of morphoklines, see 1st diagram below)

Homalocnemis  nigripennis,  Empididae.
Length about 5 mm.
Radial Sector (RS) still 3-branched, but fork of R4+5 shortened. R3 absent.
M1, M2, and M4 present. M3 absent. Discoidal cell still present.  tb1 [= base of M4] suppressed.  tb2 [= m-cu] present. CuA and 1A converging, but not reaching hind-margin, i.e. the common stalk has disappeared.

The wing-venation of this species is not derivable from that of  Omphrale  (because of its three M's) but reverts back to  Spaniopsis.

(for its position in the diagrams of morphoklines, see 1st diagram below)

Systropus  excisus,  Bombyliidae.    
Radial Sector (RS) still 3-branched. R3 absent.
M1 and M4 present, M2 and M3 absent.  tb1 [= base of M4] suppressed.  tb2 [= m-cu] present. CuA and 1A with a commom stalk, reaching wing-margin.

(for its position in the diagrams of morphoklines, see 1st diagram below)

Hilarimorpha  singularis,  Hilarimorphidae.    
Radial Sector (RS) still 3-branched, fork of R4+5 short.
M1, M2, and M4 present. M3 absent.  The intermedial cross-vein tp vanished, therefore discoidal cell absent.
CuA and 1A ending with a common point in the wing's hind-margin.

As a result of the disappearance of the discoidal cell this venation is  derived (i.e. it is in a derived condition) with respect to  Homalocnemis ,  but primitive with respect to the cubital cell (this cell is still long, and is closed only at the wing-margin). So these two venations show specialization-crossing.
Also with  Systropus  the present form (Hilarimorpha) has a specialization-crossing :  the latter is derived with respect to the absence of the discoidal cell, but primitive in its number of Medial branches.

(for its position in the diagrams of morphoklines, see 1st diagram below)

Cyrtosia  meridionalis,  Bombyliidae.    
Radial Sector (RS) has become 2-branched by loss of R4.
M1, M2, and M4 present. M3 absent.  The intermedial cross-vein tp vanished, therefore also in this form discoidal cell absent.
CuA and 1A ending closely together in the wing's hind-margin.

As a result of the disappearance of the discoidal cell also this venation is  derived  with respect to  Homalocnemis,  but primitive with respect to the cubital cell, i.e. this cell has not yet been closed. And the present venation also has a specialization-crossing with that of  Systropus (number of branches of RS and M).

(for its position in the diagrams of morphoklines, see 2nd diagram below)

Clinocera  inermis,  Empididae.
Subcosta and R1 shortened. Radial Sector (RS) still 3-branched.
M1, M2, and M4 present. M3 absent. Discoidal cell still present.  tb1 [= base of M4] suppressed as in  Homalocnemis as a result of M4 now forming the posterior margin of the discoidal cell.  tb2 [= m-cu] present. CuA and 1A converging and coalescing more or less close to wing-base with a common stalk, which does, however, not reach the hind-margin of the wing.

This form cannot actually be derived from  Cyrtosia  and neither from  Hilarimorpa,  because it again has a discoidal cell. It may be derived from  Homalocnemis  or from  Systropus (but less so from the latter, because of the number of branches of M ).

(for its position in the diagrams of morphoklines, see 2nd diagram below)

Dolichocephala  irrorata,  Empididae.
Subcosta and R1 markedly shortened. Radial Sector (RS) still 3-branched if not counting R3 (branching off from R2+3 and coalescing with R4). This R3 may be just an atavism, i.e. a  re-activation of R3's old bed, and therefore not a primitive feature but a newly-formed [and evolutionarily merely temporary] structure.
M1, M2, and M4 present. M3 absent. Discoidal cell still present.  tb1 [= base of M4] suppressed.  tb2 [= m-cu] present. CuA and 1A converging and coalescing already at wing-base with no common stalk.

(for its position in the diagrams of morphoklines, see 2nd diagram below)

Chelifera  melanocephala,  Empididae.
Subcosta, and especially R1 not so much shortened as in  Dolichocephala.  Subcosta ending up in R1. Radial Sector (RS) 3-branched.
M1, M2, and M4 present. M3 absent. M1 and M2 with a common stalk branching off from discoidal cell.  tb1 [= base of M4] suppressed.  tb2 [= m-cu] apparently present as a stretched-out vein, such that it is a continuation of CuA. The latter sharply bends towards 1A forming with it a triangular cubital cell. The common stalk of CuA and 1A is short and does not reach the wing-margin.

This form stands more or less on itself, but may nevertheless be placed in the present derivational line.
The next form also stands more or less on itself because it has well-developed anal lobe.

(for its position in the diagrams of morphoklines, see 2nd diagram below)

Gloma  fuscipennis,  Empididae.
Subcosta ending up in the Costa again and runs close to R1. Radial Sector (RS) still 3-branched.
M1, M2, and M4 present. M3 absent. Discoidal cell still present.  CuA strongly curving back on 1A, their common stalk not reaching wing-margin.

(for its position in the diagrams of morphoklines, see 2nd diagram below)

Hormopeza  obliterata,  Empididae.
Radial Sector (RS) still 3-branched. R2 running close to R1
M1, M2, and M4 present. M3 absent. Discoidal cell still present.  CuA, as in  Gloma, strongly curving back on 1A, their common stalk hardly reaching wing-margin.

(for its position in the diagrams of morphoklines, see 2nd diagram below)

Leptopeza  flavipes,  Empididae.
Subcosta ending up in R1. Radial Sector (RS) becomes 2-branched, because of the disappearance of R4 (or of its coalescence with R5).
M1 almost competely reduced, M2, and M4 present. Discoidal cell still present.  CuA strongly curving back on 1A, their common stalk not reaching wing-margin.

(for its position in the diagrams of morphoklines, see 3rd diagram below)

Sciopus  albifrons,  Dolichopodidae.
Subcosta ending up in R1. Radial Sector (RS) 2-branched.
M1 and M2 having a common stalk branching off from the discoidal cell.  M1 curves up towards R4+5 (or R5), as it does in many higher flies.  M4 present. This is a more primitive configuration -- as to the number of Medial veins -- than it is in  Leptopeza (Empididae). Discoidal cell still present.  Cubital cell very small, i.e.CuA strongly curves back on 1A already at the very base of the wing. Their common stalk not reaching wing-margin.

Despite the more primitive structure of M1 and M2, the present form is clearly  derived  with respect to  Leptopeza  by the strong shift of the cubital cell toward the wing-base.
From this venation that of the following is clearly derivable.

(for its position in the diagrams of morphoklines, see 3rd diagram below)

Dolichopus  picipes,  Dolichopodidae.
Subcosta ending up in R1. Radial Sector (RS) still 2-branched.
M2 vanished. M4 still present. Common stalk of CuA and 1A longer than in  Sciopus, but still not reaching wing-margin.

(for its position in the diagrams of morphoklines, see 3rd diagram below)

Rhamphomyia  platyptera,  Empididae. Wing of male.
Subcosta ending free. Radial Sector (RS) 2-branched.
M1, M2 and M4 present. Discoidal cell still present. Cubital cell as in  Hormopeza  or  Leptopeza. Common stalk of CuA and 1A reaching wing-margin.

This form can best be derived from  Hormopeza.

(for its position in the diagrams of morphoklines, see 3rd diagram below)

Microphorus  velutinus,  Empididae.
R1 very close to Subcosta. Radial Sector (RS) 2-branched.
M1, M2 and M4 present. Discoidal cell still present. Cubital cell and posterior basal cell (= the cell lying directly above the cubital cell) strongly shifted to wing-base.  CuA and 1A (forming the cubital cell) without common stalk.

The next form (Hybos) stands more or less on its own because of the long CuA. It nevertheless has qualitative affinities with  Leptopeza.

(for its position in the diagrams of morphoklines, see 3rd diagram below)

Hybos  culiciformis,  Empididae.
Subcosta free. Radial Sector (RS) 2-branched.
M1 and M4 present. Discoidal cell still present. CuA long and curved, not reaching wing-margin. 1A absent.

As has been said, this form stands more or less on its own because of the long CuA (i.e. the long cubital cell if 1A were present). It nevertheless has qualitative affinities with  Leptopeza.

The next form may more or less be derived from  Gloma.  It has lost the discoidal cell.

(for its position in the diagrams of morphoklines, see 3rd diagram below)

Bicellaria  nigra,  Empididae.
Subcosta ending up in the Costa. Radial Sector (RS) 2-branched.
M1, M2 and M4 present. The intermedial cross-vein tp has vanished, therefore this form does not have a discoidal cell anymore. CuA strongly bent backwards to 1A, forming the cubital cell. Their common stalk reaching wing-margin.

As has been said, this form may more or less be derived from  Gloma.

The next form might be derivable from  Chelifera  earlier in this line.

(for its position in the diagrams of morphoklines, see 4th diagram below)

Hemerodromia  raptoria,  Empididae.
Subcosta absent. Radius (R1) short. Radial Sector (RS) still 3-branched.
M1, M2 and M4 present. The intermedial cross-vein tp has vanished, therefore this form does not have a discoidal cell anymore. The cross-vein tb1 (= base of M4) is still present, or we might interpret this feature as follows :  Like in Chelifera the base of M4 is suppressed while the the base of M3+4 is still present, meaning that also in  Hemerodromia  the apparently preserved "base of M4" is in fact the base of M3+4.
The cross-vein tb2 (= m-cu) is present, but the latter has been stretched such that it has become the continuation of the [chief part of the] vein M4 while smoothly going over into CuA, resulting in a single longitudinal vein composed of CuA, m-cu, and M4.
CuA doesn't bend down (its curved end-piece is missing) and 1A has disappeared, so there is no cubital cell.

Because of its 3-branched Radial Sector this form cannot be derived from the previous one (Bicellaria). So it reverts back to  Chelifera  above.

The empidid wings that follow are similar to the present form but the Radial Sector has become 2-branched, M2 vanished, but in some species a remnant of the cubital cell is still present (while it is completely absent in Hemerodromia).

(for its position in the diagrams of morphoklines, see 4th diagram below)

Coryneta  stigma,  Empididae.
Radial Sector (RS) has become 2-branched.
M1, and M4 present. M2 disappeared. So the Media has become 2-branched.  CuA sharply bends down to 1A, forming a short cubital cell.  1A apparently not reaching wing-margin.

(for its position in the diagrams of morphoklines, see 4th diagram below)

Dysaletria  atriceps,  Empididae.
Radial Sector (RS) 2-branched. Media 2-branched.
1A apparently weakly present, and so the cubital cell.

(for its position in the diagrams of morphoklines, see 4th diagram below)

Tachypeza  heeri,  Empididae.
Radial Sector (RS) 2-branched. Media 2-branched.
1A apparently absent, and so the cubital cell.


Intermezzo
The last three forms, Coryneta, Dysaletria, and Tachypeza (Empididae), and all the next (13) ones  (see further below), that is, species of Tachista, Coryneta, and Stilpon (Empididae), are, as to the venational scheme of their wings -- two long branches of RS, radio-medial cross-vein, two long Medial veins connected by what seems to be a cross-vein (base of M4?), and strongly reduced cubital-anal veins -- almost identical to a number of  acalyptrate flies, such as certain Lauxaniidae, Tylidae, Agromizidae, and Chloropidae, except for the fact that in these the cross-vein connecting the two medial veins is the intermedial cross-vein, meaning that the discoidal cell in the wings of these acalyptrates is still present, and further that the remnants of the cubital-anal veins are still more clearly present in them :

Lifting lightly-veined wings (muscoid functional type, see later documents) of representatives of the tyloid, agromyzoid, and chloropoid subtypes. From top to bottom :
Geomyza  angustipennis Zett. Lauxaniidae. Length about 2 mm.  (After Rübsamen, from Czerny)
Tylos  corrigiolatus L. Tylidae. Length 4 mm.
Phytomyza  kamtschatkensis Hend. Agromyzinae. Length about 1 mm.  (After Hendel)
Agromyza  frontella Rond. Agromyzinae. Length about 2 mm.  (After Hendel)
Chlorops  sp.  Chloropidae. Length 2.5 mm.
(From ROHDENDORF, 1951)

To these we may add (also acalyptrates) :

Lifting lightly-veined wings (muscoid functional type) of representatives of the drosophiloid, asteioid, and sphaeroceratoid subtypes from the family Drosophilidae. From top to bottom :
Drosophila  sp.  Drosophilinae.  Length 4.5 mm.  (range of Radial veins indicated by a brace)
Periscelis  annulipes Lw.  Periscelidinae.  Length 3.75 mm.  (After Duda)
Dinomyia  ranula Lw.  Canaceinae.  Length about 1.75 mm.  (After Becker)
Astiosoma  rufifrons Duda.  Asteiinae.  Length 2.25 mm.  (After Duda)
Asteia  concinna Meig.  Asteiinae.  Length about 2.8 mm.  (After Duda)
Limosina  sp.  Sphaeroceratinae.  Length 3 mm.
(From ROHDENDORF, 1951)

and finally the acalyptrates :

Lifting lightly-veined wings (muscoid functional type) of representatives of the anthomyioid subtype.
Top image :  Dichaeta  caudata Fall.  Ephidridae.  Length 4 mm.  The Ephydridae is a highly versatile family of at least 1000 species.
Bottom image :  Sepsis  communis Meig.  Sepsidae.  Length 2.25 mm.
(After ROHDENDORF, 1951)


It is interesting to realize that the empidoid wings (in our derivational line) belong to species of the family Empididae which itself belongs in the suborder Brachycera orthorrapha, while the above examples of wings of acayptrate flies all belong to families that themselves belong in the suborder Brachycera cyclorrapha (true flies, higher flies) and functionally to the lifting lightly-veined (muscoid) wing-type. So virtually the same wing-venation is found in (otherwise) very different flies. If we think of a derivation of one from the other then it might be from acapytrate wings to corynetoid wings (the latter belonging to genera such as Tachista of the family Empididae).
(end intermezzo)

The next forms of  empidoid wings  (continuing the above derivational line of empidoid wings) have (vitually) no trace of the cubital cell anymore. They illustrate the same venation realized in wings of various shapes (as did the examples from the acalyptrates just given).

(for the position of three of them in the diagrams of morphoklines, see 4th diagram below)

3 - Tachista  annulimana,  Empididae.
4 - Tachista  brevipennis,  Empididae.
5 - Tachista  calcanea,  Empididae.
6 - Tachista  connexa,  Empididae.
7 - Tachista  costalis,  Empididae.
8 - Tachista  interrupta,  Empididae.
9 - Tachista  ornatipes,  female.  Empididae.
10 - Tachista  sabulosa,  Empididae.
11 - Tachista  terricola,  Empididae.

In the next two Corynetas (one of them already earlier depicted) the cubital cell is still more or less present :
12 - Coryneta  cursitans,  Empididae.
13 - Coryneta  stigma,  Empididae.

14 - Stilpon  lunata,  Empididae.
15 - Stilpon  nubila,  Empididae.

The last forms depicted, 3-11 (Tachista), 12-13 (Coryneta), and 14-15 (Stilpon) need not be included in our derivational line 1, because they differ little from  Tachypeza, the last member of the line.  In fact they are all purely parallel, i.e. repeated, developments.


The corresponding four diagrams of morphoklines are then (see the above derivational line from top to bottom) :

REMARK :  In this last diagram we have, for instance, T, Hemerodromia, that has not noëtically originated from J, Chelifera, but from J1, which looks like J.  But in the first diagram we had K, Gloma also originated from J1.  So in the last diagram the naming J1 (and all items here involved) should be changed (as we had done in similar cases). But in order not to complexify matters still more we don't do it. And after all, it is certainly conceivable that from one and the same species/strategy, for instance J1, may originate more than one derived species/strategies.

It is not easy to fully express the stronger or looser derivational relationships as they were depicted in the above derivational line -- mainly consisting of empidoid venations -- in diagrams of morphoklines. The corresponding diagrams of morphoklines therefore mainly express the polyphyletic development -- in the Implicate Order -- of these species. The sequence in the derivation line of existing species and their venation is supposed to more or less reflect the courses of these (polyphyletic) noëtic transformations. What we actually "see" -- in the Explicate Order -- is not evolution, i.e. not the transformation of one form from another -- but the sequence of appearance, in the Explicate Order, of different species and types.

*  *  *


With all this we have concluded our exposition of empidoid wings. In the next document we will consider the large muscoid wing-type, which has its origin in certain empids.

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