G. C. Crampton.
A Phylogenetic Study of teh Mesothoracic Terga and Wing Bases in Hymenoptera, Neuroptera, Mecoptera, Diptera, Trichoptera and Lepidoptera.
Psyche 26:58-64, 1919.

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58 Psyche [June
Fig. 1.
Diagrammatic figure of the posterior respiratory organ of a dipterous larva indicating the several diagnostic characters. *Diameter of circular plate. 1, 2, 3, 4, first, second, third and fourth interspiracular spaces of left stigmal plate. I, 11, 111, dorsal, median and ventral slit-like spiracles, respectively, of right stigmal plate.
IV, the left circular plate or "button." Fig. 2. The micro-protractor showing arrangement of ruled angles. The various possible combinations from 5' to 360' indi- cated by the concentric lines.
A PHYLOGENETIC STUDY OF THE MESOTHORACIC TERGA AND WING BASES IN HYMENOPTERA,
NEUROPTERA, MECOPTERA, DIPTERA, TRICHOP- TERA AND LEPID0PTERA.l
In several papers dealing with the phylogeny of insects, the Hymenoptera, Neuroptera, Mecoptera, Diptera, Siphonaptera, Trichoptera, Lepidoptera and their allies were grouped in a super- order called the "Panneuroptera." A portion of the evidence for such a grouping, based upon the study of the genitalia of males, has already been presented in Psyche, Vol. 25, p. 47, and in the Proc. Ent. Soc. Washington, Vol. 21; and in the present paper, I would briefly review the evidences of relationships indi- cated by the nature of the mesothoracic terga and wing bases in these insects. The terminology here adopted is that previously applied to the terga and wing bases of the Embiidse, Plecoptera, Coleoptera and Dermaptera (Psyche, Vol. 25, p. 4), the Blattidse, Plecoptera and Neuroptera (Jour. N. Y. Ent. Soc., Vol. 24, p. I), the Orthoptera (Ann. Ent. Soc. America, Vol. 11, p. 347), and the Hymenoptera and Diptera (Jour. N. Y. Ent. Soc., Vol. 22, p. 248). In the lower insects, the metathorax is subequal in size to the mesothorax, and in a few instances is even larger than the meso- thorax. In the insects here considered, however, the mesothorax is usually the larger of the two, and since the metathorax becomes 1Contribution from the Entomological Laboratory of the Massachusetts Agricultural College, Amherst, Mass.
Pu&e 2658-66 (1919). hup Ytpsychu einclub orgt26?26-058 html



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PSYCHE, 1919.
VOL. XXVI, PLATE I.
WID TH OF'
~~~c~~P--Respiratory Apparatus of Dipterous Larvae.



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19191 Crampton-Terga and Wing-Bases of Insects 59 reduced to a narrow transverse band in the tergal region of the Diptera, I have restricted the present discussion to the mesonotum alone, since it is usually well developed in most of the insects of this group.
In the mesonotum of the insects here discussed, there is a tend- ency for the prescutum (" psc," Figs. 1,3,5, and 6) to become pro- longed further backward into the scutal region "sc," thereby be- coming longer than broad, while in the lower insects it is frequently broader than long. On the other hand, the scutellum, "sl," which may become very narrow and prolonged far forward into the scutal region, "sc," in such lower insects as the Blattidse, etc., in the insects here discussed tends to become somewhat broader than long. The mesothoracic postscutellum, "psl," is usually unde- veloped in such lower insects as the Blattidse, Mantidse, Acrididse, Dermaptera, Coleoptera, etc., but in the Embiidse and Plecoptera it is quite well developed, as in the insects under consideration. The mesothoracic tegula "t" is frequently quite large in the insects under discussion, and is usually developed only in the mesothorax, while in the lower forms, it is usually small, or not developed in the mesothorax, although in some cases it may be developed in both meso and metathorax in the lower insects. The sclerite labeled "a" in Figs. 1, 2, 4, etc., is usually not well developed in lower insects, while in many of the higher insects it is quite large, its better development in the latter insects being probably correlated with the superior powers of flight in the higher forms. I have not observed the middorsal suture "ms" in many lower insects (excepting the Plecoptera and Embiidse), while it appears to be present in many of the higher insects, although it is not present in all of them. As may be seen from the accompanying diagrams (Plate 11) the general plan of the sclerites is relatively simple, and is adhered to quite closely by most of the insects here shown. It is thus a much simpler matter to compare the different insects together in at- tempting to trace their paths of development than is the case with the wing venation, where the complex and intricate patterns, with their bewildering array of modifications, make it very difficult to trace out the paths of development followed by the different groups of insects, unless one has practically all of the intermediate stages; and even then he may be led astray by the study of only one set of



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primitive in respect to one parkicuhr featurn, may be m1athely one mmce merely serving to check that dram from other sources. On this accounty I would present the evidene furnished by a study asme a trimgulav outline, ,and the e
)roach each other near the middle of the



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shown in Fig. 5 this is not the caw, due to the fact that it waa chosen to illustrate the tendenq in some Newoptera for the wing bme and tergum h approach the condition mmming in certain Mecoptera md Diptera.
In both the Trichoptma (Fig. 9) md
the hpidopter~ (Fig. 4) there is a mked tendency for the kgda "t " to become large-& tendency which is somewhat less developed in the Hymenoptera (Fig. I) and in ce&h Neuroptera, dtho~~gh there are evidences of it in these in*& as well. The teguIa, however, is best developed in the Trichoptem and Lepidopkra, and in &eae ins&å the region labeled "s" (Figs. 9 and 4) is vmy similar in outline, as is true of the incision in the margin of the region immediately bhind that labeled "s.*' In both Trichop- tera and hpidoptma (Figs. 2 and 4) the alar ossicle Meled "n" is comparativeIy well devdopd, aa is ah h e of the scImite labeled $'a"; and in both Trichoptera and Lepidoptexa, there ig a mark4 tendency toward the formation of a membranous area "ma" (Figs. 9 and 4) in the postwut~lhr region ‰ÛÏpsi. The above-mentioned dmihities between the Trichoptera and bpidopkra are in full mcod wit& the evidenm of close relatian- ship d~aun from other sources, such m the preseuw of a miled probowis in such Trichoptma as Pkxf~ofmms pmmhsti, the lepidoptemid character of the venation and wing-outlines of cer- tain Trichoptem, the simiIarity in the mtenm, legs, genitalia, outline of the abdomen, and other featum which point very clearly ta a community of descent, or a merging of the lines of descent of the hpidoptera md Trichoptera as they are traced back to their point of origin; and (as haa keen pointed out in a papF soon to be published in the Trans. Ent. Sm. Landon, dealing with the phylogeny and in~~timships of the higher in&) these matmni&tl featurea d the adult insects, aa well as the study of larval &a&m, clearly point to the Trichopha rather than the Mecopterm m the stem fom from which Lqidopba have sprung, despite the ehrh of Handlirwh and Tillyard to emphmize the rnecoptmid chmter of the venation of the Iepidopterous wing. The Mwoptem me also related to the Lepidoptera, but less closely than the Trichoptera axe, and I am more inclined to regard the lines of demt of the Mecoptern, Trichoph, and lipid~rma as springing off from a cornon point of a stem re- sembling the Neriroptm% very cl~ly, though the linea of descent



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of the Trichopma and Lepidoptera appear to merge in a single line tw we trace them back to this common point of origin. The mesothoracic terga md wing biwea of tipdid Diptent and the B&mdike Mmoptm are strikingly &nilar (Figs. 3 and 6). In both of these tps of iweets, the mea~thorack twga become very elmgate* and the wing k s home shifted backward by thee1ongationof theprescutdregion "pc" (Figs.3 and 6). The whg bases are also &her nmw or constricted in these insects, as is indicated by the extent of the hrd bhk line bordering the cut afT wings in Figs. 3 and 6. A similar tendency is shown in the Xewopkmn depicted in Fig. 5, md it is quite psibIe that the nemopterid Newoptem resemble the common ancestors of Mecop- *era and Diptem in some mpecta, especially in the evident tend- ency toward the elongation of the head region md the reduction +
of the hind wings to nmw ribbon-like stmdum, which is cmried s
3
3
1
-
#ti11 further in ihe Diptera. The outline of the mtellnm "d" i very similar in fie Dipteran and Mmopterort shorn in Figs. : and 6% and the bulging region bearing the 1dxl "psl" in Fig. apparently comesponds to the median region laheld "mt" i~ Fig. 6. The whites desipnted as "prt'' in fig. 3 pmbab!y mr mwmd +n+hne bminm the esm~l~bl in Fin 6 The nwwih su.,y ".*.. .., --.,-- --.+-.**e *--- --- ---* -- -am. -. --.. r-.,-v-- 1
region "pc" tends to assume a similar outline in both inwcts, the tegula "t" is small in both, and the ah- ossicle "n" is not ptly developed in either of these inmh. The outline of the tergum, and the nature of the wing bases aa well aa the featum mntioned above would indicate a close reIationship hetween the tipdid Dip- ha and the Bitiw-like Memptera, 4 this is borne out by the natum of the head, m h n ~ , mouthpmts, legs genitalia and character of the &domen in the two goups, so that the markd similarity in qipearmce between Bttams and the lower Diptera is not merely a superkial resemblance, hut extends to the mme minute details na well. 1 wmld therefom maintain that the linea (
Mmptera and Diptern merge rn we trace
1
mon origin, and the Newoptera appear to
be as mucn mze cumman stock as any other insects, from which the lines of development of the Trichoptma and Lepidoptera, and the Mecoptera and Diptera, ha* sprung.
The tergurn of the Hymenoptma (Fig, 1) is as mu& Eke that of the Newoptera (Fig. 5) rn my, a d in general, the Hymenoptma



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seem k be qtite closeIy related to the Newoptera. The line of dewlopmat of the Hymenoptera therefom probably arose near the base of the neuropteroid stem, though the Hymenoptera me in some respects intemediate betwmn the Nemopkra and the Pmcid~. The Hymenoptera have m y charwters suggative of affinities with the Mwptera, dtho~gh the Mecoptemn ~hom in Fig. 3 is not so we11 suited as Pawpoiks and other primitive Mecopha for demonstrating this reMon&ip. Since the mecop- bran line of devdopmmt originated at a point quite far down on the main neurciptemn stem, it is merely to be suppod that the &Iemptera will show evidenws of a rather close relationship to the Hymenoptem, which dm mupy a position far down this main stem, md siddy, since the Trichoptem branched off from this main stem very near tbq point of migin of the Mecopha, both Trichoptem and Mecop- ahow indications of d3initie.a with the Hpemptera RA we11 as with the Neuroptem; but the resemblances between the Hpenoptera, Mecoptera and Trichopkra are the most patent in the lmd stages of these insects. Since the Hymen- optma resemble Mecoptent in some respecb, and since the Diptma also resemble. Mecoptera in mmy mpcts, it is to be expected that there will be certain points of ~semblmm behem the Hpenop tera md Dipbra dso; but 1 do not consider that the Hymenoptera and Dipkera are w chely rehbd aa MacGiUivray and other students of the wing venation have hen led to suppose, from the& , studia of this one set of ~tructures done. That the Siphonaptera -
(the %em) were descended from Dipka-like ancestors is admitted by prwtica1Iy all recent investigators; but she these foms are wingless, it has not seemed dvisabIe ta include a study of their bga in a paper ddhg largely with the wing-basm. The evidence of xelationship among the insects here &-d, as indicated by a study of the krga and wing haws, is in full accord with the evidenm from other stmctums as well, and the eonclwiom here reached may b bidy summuid ns follows. The Neuropbra are a~ primitive as any representatives of the superorder (the Pameuroptem), and probably have departed aa Ettle as any from the condition typical of the fom ancestral to the group as a whole. The Hymenoptera are a h very primitive, and occupy a pmition far down on the main newoptemid akm, The Mecoptera and Trichoptera arose from newopteroid mcestom,



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64 Psyche [June
and are also related to the Hymenoptera. The line of develop-
ment of the Diptera merges with that of the Mecoptera, and the line of development of the Lepidoptera merges with that of the Trichoptera as all of these are traced back to the common neurop- teroid stem. The Trichoptera are probably a little more closely related to the Neuroptera than to the Mecoptera, but their line of descent branched off from the common neuropteroid stem very near to the point of origin of the mecopteron line of development on the same neuropteroid stem. There are some reasons for re- garding the Mecoptera as the stem forms from which the lines of development of the Diptera, Trichoptera and Lepidoptera have sprung; but the Neuroptera are on the whole as near as any, to the ancestral forms from which all of these insects are descended. a. = Adanal process or ossicle pf. = Prescutal fontanelle. (adanale). PO. = Posttergite.
j. = Juxtategula.
prt. = Pretergite.
m, = Median ossicle (medip- ps. = Parascutellum. terale) . psc. = Prescutum.
ma. =Membranous area of post-
psl. = Postscutellum.,
scutellum. pt. = Parategula.
ms. = Middorsal suture.
ptg. = Postalare or pleurotergite.
mt. = Meditergite.
s. = Suralare.
n, = Notopteral ossicle (notop-
sc. = Scutum.
terale) . sl. = Scutellum.
pa, = Prealar bridge (prealare) .
so. = Scutal organ.
t . = Tegula.
Fig. 1.
Mesonotum and wing-base of the Hymenopteron Ceplz- aleia.
Fig. 2.
Mesonotum and wing-base of the Trichopteron Neu- ~onia.
Fig. 3.
Mesonotum and wing-base of the Mecopteron Bittacus. Fig. 4. Mesonotum and wing-base of the Lepidopteron Phassus.
Fig. 5.
Mesonotum and wing-base of the Neuropteron Nemop- tera .
Fig. 6.
Mesonotum and wing-base of the Dipteron Tipula.



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PSYCHE, 1919.
VOL. XXVI, PLATE 11.
C~~~~~~~-Mesothoracic Terga and Wing-Bases,



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