G. C. Crampton.
A Comparison of the External Anatomy of the Lower Lepidoptera and Trichoptera from the Standpoint of Phylogeny.
Psyche 27(2-3):23-34, 1920.

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PSYCHE
VOL. XXVII . APRIL-JUNE, 1920
Nos. 2-3
A COMPARISON OF THE EXTERNAL ANATOMY OF
THE LOWER LEPIDOPTERA AND TRICHOPTERA
FROM THE STANDPOINT OF PHYLOGENY.
BY G. C. CRAMPTON, Pn.D.,
Massachusetts Agricultural College, Amherst, Mass. Dr. August Busck and Dr. Bethune-Baker have very generously furnished the material upon which the following observations on the Lepidoptera were based, and Mr. Nathan Banks has kindly identified the adult Trichopteron described in the following dis- cussion. To these gentlemen I would express my very sincere gratitude and appreciation for their generous assistance which has made this study possible.
One hundred years ago, that keen observer Leach, 1817 (2061. Misc., Vol. 3) linked together the orders Trichoptera and Lepi- doptera in a group to which Haeckel, 1896, applied the term "Sorbentia"; and most entomologists since Leach's time have agreed in regarding the orders Lepidoptera and Trichoptera as extremely closely related. Speyer, 1839 (Oken's Isis, 1839, p. 94) was, so far as I am aware, the first to suggest that the lepidopterous "family Micropterygidseyy forms a transitional group leading to the Trichoptera, and later in 1870 (Stett. Ent. Zeit., 1870, p. 202), he carried the comparison between the two groups still further. Subsequent investigations have served to confirm Speyer's views, and since the micropterygoids occupy such an important position from the standpoint of the phylogeny of the Lepidoptera, their affinities have been much discussed.
Chapman, 1894 (Trails. Ent. Soc. London, p. 335) divides the micropterygoids into two families, the Micropterygidse and Erio- cephalidse. Meyrick, 1912 (Genera Insectorurn, Fmc. 132) treats them as a single family, the Micropterygidse, and divides them into three subfamilies, the Mnesarchseinse, Eriocranianse and Microp- teryginse. In the following discussion, these insects (which belong Pu&e 27:23-M (1920). hup ttpsychu einclub orgt27t27-021 html



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to three distinct families) 'will be treated as comprising a single superfamily, the Micropterygoidea, which constitutes the lepi- dopterous suborder Prolepidoptera.
Packard, 1805 (Monogr. Bornbycine Moths, Part 1, Noto- dontidse) makes E~ocephdta colfkella the "type" of a distinct suborder of Lepidoptera which he calls Lepidoptera laciniata, or Protolepidoptera, while he places Micropteryx in another suborder' which he calls the Paleolepidoptera. Chapman, 1916 (Trans. Ent. Soc. London, 191 6-1917, p. 310) raises Micropteryx to ordinal rank, proposing for it the name Zeugloptera, thus differ& from practically all of his predecessors, who agree in regarding the micropterygoids as lepidopterous.
On page 307 of Part I1 of his treatise on Insects (Cambridge Nat. Hist.), Sharp, 1909, in discussing the fact that Brauer's distinction between the Lepidoptera and Trichoptera on the basis of the presence of mandibles in the pup% of Trichoptera no longer holds good, makes the statement that "unless it should be decided to transfer Micropteryx to Tnchoptera, and then define Lepidoptera and Trichoptera as distinguished by the condition of the pupa, it would appear to be very difficult to retain the two groups as distinct." On page xvii of the Proceedings of the Ent. Soc. of London, Sharp, 1896 had likewise suggested that the microptery- golds "should be treated as a group of Trichoptera whose larvse are not aquatic in habits." Cornstock, 1918, in his book on the "Wings of Insects," has followed these suggestions, treating the .
Mimopterygina as a suborder of the Trichoptera, and referring to them as ternatrial Trichoptera. In reviewing Cornstock's book, Tillyard, 1919 (Ent. News for May, 1919, p. 149) criticizes him for removing the micropterygoids from the Lepidoptera to the Trichoptera from the study of the wing-veins alone, and states that "even from the point of view of the wing-venation it is scarcely defensible, for a careful study of the freshly turned pup= of any of the older families of Lepidoptera will show that their wing- tracheation agrees closely with that of MtCTovieryx, particularly in the different courses of Cu and I A in fore and hind wings. Moreover the pupal wing of Microyteryx has acomplete tracheation; the imaginal wings have broad well developed scales of a higher type than any found in die Trichoptera; the fore wing does not possess a separate M4; and the hind wing has a definite frenulum.



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1920] Crampton-Lower Lepidoptera and Trichoptera 25 In all these points this family is definitely Lepidopterous. Neither the larval form nor the imaginal mouthparts are Trichopterous, so that there is really no justification for so radical a change, which must remain as a serious blemish in a fine work." In order to test the validity of Tillyard's criticism, it has seemed preferable to examine structures other than the wing veins in com- paring the micropterygoids with the Tricoptera, and for this pur- pose, I have chosen the primitive little Trichopteron Philopotamus distinctus. These small caddice-flies are particularly interesting because the females have only rudimentary wings-a condition which, so far as I am aware, has been recorded but once before among North American Trichoptera. The bodies of both males and females are of a dusky black color, and the wings of the males are of a slightly ashen hue. Both sexes are found on stones along the banks of swiftly running streams, particularly in the neighbor- hood of waterfalls, and those found about Amherst first appear the latter part of April. The females have rather long hind legs enabling them to flee rapidly over the surface of the water with quick leaping movements, when disturbed, while the males under these conditions dart to the surface of the water, and after making a short series of "leaping" flights, come to rest on the bank a short distance from the place whence they were dislodged. At the beginning of the season, neither males nor females are readily disturbed, and may be easily captured by a quick grasp with a pair of forceps. The small white larvae which appear to be those of Philopotamus crawl over stones in swift-running brooks, and pupate in their cases made of sand, usually attached to the upper surface of stones. The pupse, if I remember aright, are protected by a parchment-like case lining the outer one made of sand. I am hoping to find out more of the life history of these insects later, since the habits and cecology of insects should be studied in addi- tion to their structures, in attempting to determine their affinities; but for the purpose of the present paper, it will be sufficient to compare the chief features of their anatomical details with those of the micropterygids.
The head capsule of Philopotamus (Plate 11, Fig. 2) is surprisingly like that of the micropterygid Mnemonica (Fig. 4) in outline, and these two types of head approach the nearest to that of the neurop- terous ithoniid Oliarces clara, Banks (an insect which should be



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26 Psyche [April- June
placed in the family Ithoniidae, judging from the nature of its thoracic sclerites, head capsule, and other features, although this has not yet been done in any grouping of the Neuroptera which I have seen thus far). In fact, it is very probable that the ithoniids are quite like the forms which gave rise to the lines of descent of the Lepidoptera and Trichoptera, though Tillyard and Handlirsch seem to think that the Mecoptera (or their fossil relatives) repre- sent the ancestors of these two groups. The galeae of the maxillae (see structures labeled "mx" in Fig. 4, of the micropterygid) are not developed in the Trichopteron shown in Fig. 2, but Ulmer, 1905 (ZoBl. Anz.28, p. 56) and Cummings, 1913 (Ann. Nat. Hist. XI, p. 308) describe the maxillae of the Trichopteron Dipseudopsis having the parts well developed, and with the galesel as long as those of Mnemonica ("mx" of Fig. 4). The pupa of Mnemonica (Fig. 9) has huge crossing mandibles suggestive of the type found in Trichoptera (Fig. 7), but I have not found any Trichoptera in which the mandibles are enlarged at the tips as in Mnemonica, nor have any of the trichopterous pupae which I have examined, a frontal process like that labeled "e" in Fig. 9 of the pupa of Mnemo+ca.
The lateral region of the thorax of Mnemonica (Fig. 1) is aston- ishingly like that of the Trichopteron (shown in Fig. 3), the out- lines of the upper and lower divisions of the mesothoracic epister- num ("aes2" and " kes2") being very similar in both instances. It may be remarked in passing, that the region labeled "aes" is not the entire episternum, nor is the region labeled "kes" the trochantin (which is labeled " tn" in both figures) as is usually stated to be the case, and the hinder portions of the coxae labeled "me" are not detached portions of the epimeron "em," which have become adherent to the coxse~but these features have been thoroughly discussed in an article dealing with the basal segments of the leg in insects (Zool. Jahrb. Abt. Anat., 39, p. 1) and need not be gone into further here.
As is true of all Lepidoptera which I have examined, the meso- thoracic merocoxa "me2" (Fig. 1) or posterior division of the coxa extends along the entire posterior border of the anterior coxal division " vc2" in Mnemonica (Fig. l), and there is no " basicoxite" 1 The proboscis of Plectrota~sus is not "coiled," as was formerly stated to be the case, but is merely folded.




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19201 Crampton~Lower Lepidwtmi awl Trichoptera 97 like that labeled "cm " in the Trichopteron (Fig. 8). On the other hand, the mexocoxa "meg" of Fig. 3 extends only port way down the remainder of the coxa in all of the Trichoptera which I have examined, and in all of them there occurs a msoihwacic basicoxite "cm " (Fig. 8) which is absent in all of the Lepidoptera I have seen. Since these features seem to be constant in the groups under discussion, they are probably diagnostic for the orders iq question, and by applying this test to the micropterygids, they are seen to be clearly Lepidoptera and not Trichoptera! I would especially emphasize the importance of this apparent1 y conclusive test, since it is the only feature (of which I have any knowledge) which hoIds good in ail cases examined, and on this account it should be of great diagnostic value in attempting to determine whether an insect is lepidopterous or trichopterous. The &gal region of the thorax is very similar in the lower Lepidoptera and Trichoptera (Figs. 5 and 81, but the mesothoracic scutellm of Mwm0n.h (Fig. 8, 4'sla"), as is the case in most of the other Lepidoptera, tends to become somewhat "transversely oval" in outline, while that of the greater part of the Trichoptera (Fig. 5, "&") is more triangular in outline. This feature may also prove to be of diapo~tic value; but I doubt that it d l be fomd to hold in all cases, although I have been unable to find any excep- tions thus far, In most Lepidoptera examined, there occurs a tegub-bearing rod labeled "t" in Fig. 8 of Mnemonics; but I do not find exactly this type of structure in most of my caddice-fly material. Both of these primitive representatives of the orders Trichoptera and Lepidoptera have a wing-coupling apparatus of the ]'urn-frenate type (i. e. both jugum " j " and frenuhun "fr" are present in the insects shown in Figs. 5 and 8) so that Tillyard's distinction between the two orders on this score, will not hold. Since I have not made a study of the wing veins, I shall not attempt to discuss this phase of the matter; but so far as the nature of the jugurn-bearing region '' jf " and the alar ossicles " np," " ba," " a," etc., are concerned, the basal portions of the wings, like the tergal sclerites, are strikingly similar in the two insects under discussion. In all of the Trichopterous larvse which I have examined, homo- logues of the styli or gonopods ("s" of Fig, 6) are to be found in the posterior region of the abdomen; but I have been unable to find these structures in any lepidopterous larvae, and since the larvse of



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28 Psyche [April-June
the micropterygids seem to lack these structures, this feature may also be of value in distinguishing between the orders Lepidoptera and Trichoptera. The styli labeled "s" in the larva shown in Fig. 6 are apparently represented by the so-called gonopods, or gonostyli "s" of the adult male Trichopteron shown in Fig. 15 (Plate 111). Even when the gonopods "h" are well developed in .male Lepidoptera (Fig. 13), they apparently retain only one dis- tinct segment "h," while in those Trichoptera in which the gono- pods are exceptionally well developed, the gonostyle portion labeled "s" in Fig. 15, usually consists of two distinct segments. Furthermore, the dorsal lobes "sg" are of a different type in the two groups of insects, and these features may be of some value in further distinguishing between the Lepidoptera and Trichoptera. McLachlan, 1874-1880 (Monographic Revision of the Trichop- tera) on page 206 states that "Enoicyla is the only authenticated example of terrestrial habits in the larvae of recent Trichoptera. . . . The genus is scarcely less remarkable by its practically apterous female. . . . The pupae . . . have very distinct spiracles. . . . The larva lives under moss, etc., at the foot of trees, chiefly in woods, and often at great distances from water." Since some of the larvae of the micropterygoids feed on mosses (Musci) and occur in somewhat similar locations, these facts lend additional weight to the view that Trichoptera and Lepidoptera are very closely related.
In discussing the protocerebrum of Micropteryx, Buxton, 1917 (Trans. Ent. Soc. London, 1917-1918, p. 135) states that "In ~icro~ter~x' paired ocelli are present, but the median ocellus is not developed here, or in any other Lepidopteron or Trichopteron." This is very probably true of the Lepidoptera as a whole, but I find a median ocellus in many Trichoptera (see Fig. 11 of article on head region of insects in Annals Ent. Soc. America, 1917, p. 339, and Fig. 2 of the present paper). If no median ocellus occurs in any Lepidopteron, and does occur in some Trichoptera, this may be regarded another feature of some value in distinguishing between the orders.
Mr. Banks has called my attention to the fact that "scales" occur on the wings of certain Trichoptera, and their presence is therefore not diagnostic for the order Lepidoptera. Thus McLachlan (1. c. p. 274) in describing the trichopterous genus



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19201 Crampton-Lower Lepidoptera and Trichoptera 29 Lepidostoma speaks of the wings of the male as "clothed with 99
scattered black 'scales' regularly placed . . . , and some- what similar " scales" occur in certain Leptocerids as well as in the Sericostomatid mentioned above. It must be admitted how- ever, that the "scales" of Trichoptera are not exactly like those of Lepidoptera (see Kellogg, 1895, American Naturalist), though their function in certain cases (e. g. androconia-like structures of Mystacides wing, described by Kellogg, 1895) may be very like that of the scales of Lepid0ptera.I
Cummings, 1914 (Proc. 2001.
Soc. London, 1914, p. 461) states that "The occurrence of typical unicellular scent glands at the bases of hairs in Trichoptera as well as Lepidoptera is interesting, and in view of the close relationship between these two orders not wholly unexpected. . . . In Sericostoma they (scales) occur on the maxillary palpi, a position in which, I believe, they are undescribed in Lepidoptera." The absence of scales from the maxillary palpi in all Lepidoptera and their presence in some Trichoptera, may prove to be another distinguishing feature in defining the two orders. From the foregoing discussion .it is quite evident that the simi- larity in the head capsule, the general character of the mouthparts (both adult and pupal), the nature of the thoracic sclerites, the wing venation and presence of a coupling apparatus of the primi- tive jugo-frenate type, the general character of the terminal ab- dominal structures, and the occurrence of moss-inhabiting larvae, are features indicating an extremely close relationship between the lowest Lepidoptera and Trichoptera, so that Comstock's removing the micropterygoids from the Lepidoptera to the Tri- choptera has considerable justification. On the other hand, the subdivision of the mesothoracic coxa for its entire length, into eucoxa "vc" and merocoxa "me" (Fig. 1) in all Lepidoptera studied, and the merely partial subdivision of the mesothoracic cox= of all Trichoptera examined (Fig. 3 "vc" and "me "), to- gether with the presence of a basicoxite " cm" (Fig. 3) marked off by a downward-sweeping line of demarcation in the mesothoracic coxa of all Trichoptera studied, and the absence of this type of structure in all Lepidoptera examined furnish us with an appar- lBusck, 1914 (Proc. Ent. Soc. Washington, 16, p. 50), calls attention to the fact first observed by Spuler, that if the scales are removed from the wing of a micropterygid, its surface is seen to be covered with minute curved spines (like those of Trichoptera) occurring "between the scales and much more numerous than these."



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30 Psyche [April-June
ently decisive test for determining whether an insect is lepidopter- ous or trichopterous, and when this test is applied to the microp- terygoids, they are seen to be clearly lepidopterous, not trichop- terous! The "transversely ovate " outline of the mesothoracic scutellum (Fig. 8, ccsli') in most Lepidoptera as opposed to the triangular scutellum of most Trichoptera (Fig. 5, "slgyy), the absence of a median ocellus in all known Lepidoptera and its presence in some Trichoptera, the presence of "scales" on the maxillary palpi of some Trichoptera and their absence in all known cases in Lepidoptera, and the presence of structures homologous with the posterior abdominal styli in all trichopterous larvae ex- amined, coupled with the absence of such structures in lepidop- terous larvae are features of value serving to support the above mentioned test, when applied to the micropterygoids, and the evidence furnished by these features (which seem to have a very general application throughout the two orders) should be conclu- sive. I would therefore maintain that the micropterygoids are lepidopterous, not trichopterous, although I too would emphasize the remarkably close relationship between the lower Lepidoptera and Trichoptera (See Trans. Ent. Soc. London, 1919, p. 93). In the appended diagram (text figure 1) the lines of descent of the Lepidoptera and Trichoptera are represented as though diverg- ing from a common Lepidoptero-Trichopteron stem composed of forms combining in themselves the primitive ancestral features of the two orders. Just after these two lines of descent begin to diverge as they emerge as distinct orders (the common stem, however, was probably trichopterous) the line of development of the micropterygoids appeared, carrying over from the common ancestry many primitive features occurring in the Trichoptera, yet exhibiting certain peculiarly lepidopterous characters. The line of development of such Trichoptera as Philopotamus likewise arose very near the point of origin of the micropterygoid line of development, as shown in the diagram, but since Philopotamus' line of development is on the side of the Trichoptera, it did not acquire any peculiarly lepidopterous features, though it has developed certain features in common with all other Trichoptera, as would naturally be expected. This simple and self-evident explanation will serve to show how the micropterygoids may be truly Lepidoptera, and the Ph4lo'potamus-like forms may be truly



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19201 Crampton-Lower Lepidoptera and Trichoptera 31 Trichoptera, despite the fact that both micropterygoids and lower Trichoptera exhibit a remarkable degree of similarity; and it is therefore quite evident that it is not necessary to remove the micropterygoids from the Lepidoptera to the Trichoptera, nor is it necessary to regard them as representing a distinct order. It has seemed unnecessary to append a "bibliography" at this point, since the more important reference works dealing with the anatomy on the insects in question have been given in the text of this article. If the reader is interested in the further study of the anatomy of the micropterygoids, the following works, in addition to those previously cited, may be of interest. Walter, 1885 (Jen. Zeit. f. Wiss., 8, p. 755), on the mouthparts; Tillyard, 1918, Proc. Linn. Soc. N. S. Wales, xliii, pp. 298, and 626, for wing structures; and the excellent general description of the anatomy of all stages of Mnemonics, by Busck and Boving, 1914 (Proc. Ent. Soc. Washington, 16, p. 151).
The following list of abbreviations applies to the figures of Plate IV (illustrating the following article on genitalia of higher insects) as well as to the plates of the present paper, and will therefore serve equally well for both articles. Since homologous structures bear the same label throughout the series of figures, it will be unnecessary to give a more detailed description of the various anatomical features of the insects under discussion. MI CROPTERYGIDS PHILOPOTAMUS
Fig. 1. Lines of descent of Lepidoptera and Trichoptera.



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Psyche
[April- Ju ne
ABBREVIATIONS (PLATES 11, 111, IV) .
a. ..... .posterior notal wing process (adanale). aes ..... upper division of episternum (anepisternum) . b ..... .thread of penis (penisfilum).
ba .... .wing ossicle at base of anal veins (basanale). ....... c clypeus.
......
ca cerci.
cm ..... coximarginal sclerite (basicoxite) . ex. ..... coxa.
d ...... tergal plate and setae of ninth segment. e ...... .frontal process (frontonasus). ....
em. epimeron.
ep. ..... epiproct (uncus, tegumen, or pygidium), also proctiger or structure bearing anus.
eps ..... epipodal setae.
es ...... epicranial suture.
f ....... frons.
fp ..... .frontal (tentorial) pits.
fr ..... frenulum.
g ....... " stipes " of gonopods (gonostipes) . gp ..... genal process.
h ..... .harpago or clasp; last segment of gonopod, also called " harpes " and cochlearium.
ha ..... hypandrium, or plate under genital apparatus of male. ip ...... interpleurite.
j ....... jugum, or "clavus."
jf ...... jugum-bearing region (jugifer). kes .... .lower division of episternum (katepisternum). 1. ...... labrum.
1c. .... .lateral cervical plates.
lp ..... .labial palpus.
Is. ..... laterosternite.
.....
m .median wing ossicle (mediale).
..... md mandible.
me. ... .posterior division of coxa (merocoxa, or meron) . mp .... .maxillary palpus.
.....
mx maxilla.
. np ..... notal wing ossicle (notopterale)



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19201 Crampton-Lower Lepidoptera and Trichoptera 0. ...... ocelli.
p ...... styliger or "coxite" bearing styli (also called cardo, or gonocardo).
pa .... .parietal region of head, prealar bridge of thorax. pc ...... postcranial region of head.
pf ...... parafrons.
pfi .... .paranotal fringe (parafimbrium). pi. ..... propleuron.
pn .... .pronoturn.
pp ..... gonopleurite.
pr. .... .plates on either side of anus (paraprocts or parapodial plates).
......
ps podal setse.
....
psi. postscutellum.
pt ...... patagium, or patagial areas.
pv ..... penisvalvse, penis, sedeagus or phallus. s ....... styli, or gonopods (gonostyles). sa ..... .plate under wing (subalare).
sal .... .anterior tergal wing process (suralare). ......
sc scape of antenna.
.... set. scutum.
sg ..... .process above gonopod (surgonopod) probably homolo- gous with dorsal lobes rather than cerci. sl ...... scutellum.
. t ....... tegula-bearing rod (tegulifer) .
...... tf terminal filament (telofilum)
tg ...... tegula.
tn ...... trochantin.
.
vc . anterior division of coxa (eucoxa or veracoxa) Fig. 1. Lateral view of thorax of Mnemonia auricyanea, Wals. (Micropterygoid) .
Fig. 2. Frontal view of head of Philopotamus distinctus (Trichop- teron) .
Fig. 3. Lateral view of thorax of Philopotamus. Fig. 4. Frontal view of head of Mnemonics auriyanea, Wals. Fig. 5. Dorsal view of thorax and wing bases of Philopotamus.



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34 Psyche [April-June
Fig. 6. Lateral view of terminal structures of larval Trichop- teron.
Fig. 7. Frontal view of pupal head of Philopotamus only man- dibles shown.
Fig. 8. Dorsal view of thorax and wing bases of Mnemonica auriyanea, Wals.
Fig. 9. Frontal view of pupal head of Mnemonica auricyanea, Wals.
A COMPARISON OF THE GENITALIA OF MALE HY- MENOPTERA, MECOPTERA, NEUROPTERA, DIP-
TERA, TRICHOPTERA, LEPIDOPTERA, HOMOPTERA, AND STREPSIPTERA, WITH THOSE OF LOWER
INSECTS.
BY G. C. CRAMPTON, PH.D.,
Massachusetts Agricultural College, Amherst, Mass. Since the same plates have been used to illustrate both the present paper, and the preceding one dealing with a comparison of the lower Lepidoptera with the Trichoptera, the same list of abbreviations will serve for both papers, and by referring to the explanation of the labeling, given on page 32, this will obviate the necessity of repeating in the present paper, the list of abbre- viations there given.
For the Strepsipteron here described, I
am indebted to Dr. C. T. Brues. Dr. Bethune-Baker has loaned me the lepidopterous material used; Dr. R. J. Tillyard has fur- nished the neuropterous material; and Mr. S. A. Rohwer has furnished the sawfly material used in the preparation of this paper. Mr. Nathan Banks has very kindly identified the Trichop- teron referred to, andMr. A. N. Caudell has had the Homoptera identified for me. To all of these gentlemen, I would express my deep appreciation of their generosity and assistance so freely given. The genitalia of male insects have been discussed in several recent articles; but the correct interpretation has not been given to the parts in all cases. Recently, however, I have been able to examine a far wider and more inclusive range of forms than was at first available for study, and the added evidence, together with that furnished in Dr. Walker's excellent account of the parts of the



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