G. C. Crampton.
The Origin and Homologies of the So-called “Superlinguæ” or “Paraglossæ” (Paragnaths) of Insects and Related Arthropods.
Psyche 28:84-91, 1921.

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84 Psyche [June
THE ORIGIN AND HOMOLOGIES OF THE SO-CALLED c'SUPERLINGUA'' OR "PARAGLOSSB" (PARAGNATHS) OF INSECllS AKD RELATED IU~RTHROPODS.
BY G. C. CRANPTON, PH. D.,
J!tassachusetts Agricultural College, hnherst, Mass. In several recent papers puldished in the Fiftieth TLeport of the Entomological Society of Ontario, the T1ransactions of the Entomo- logical Society of London, and the Annals of the Entoinologica~ Society of America, I have called attention to many current niis- interpretations of the homologies of various structures in insects; but since no figures were there given, in which the parts of insects were compared with those of Crustacea and allied arthropods, 1 would present the following brief consideration of the comparative anatomy of the paragnaths (or '(superlingud') in insects, Crus- tacea, etc., as the second of a series of papers dealing vith the coinparative morphology of insects and their arthropodan relatives, from the standpoint of evolution (the first paper of the series, which deals with the evolution of the mandibles, has recently been published in the Journal of the New York Entomological Society). During the course of these investigations, it has been a source of continual amazement to me that such patently impossible, and obviously untenable views concerning the interpretation of the mouthparts of insects, as are now current among entomologists, could have gained such universal acceptance in these days of scien- tific progress, when abundant, and easily-examined material, illus- trating the true interpretation of the parts so clearly that the veried tyro could not mistake them, is available to anyone with enterprise enough to capture a comnlon mayfly naiad (nymph) from the nearest stony brook, and compare it with any common Asellt~s from the nearest pond! That this statement is not exag- gerated may be seen, for example, when one conlpares the much- misunderstood "superlingu~,'' "paraglossz~ or 'cmaxillulze'' of an insect, such as the common mayfly naiad shown in Fig. 2 (Plate V), with the corresponding parts in one of the common Ligyda exotica (Fig. 1) from the Carolina coast. The ubiquitous Asellus



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19211 Cran~pto~~-~~uperl~ngu@ or Paragloss@ of Insects 85 comrnunis, found in almost any pond, would have served equally well for the purpose of comparing the perlin lingua?' (paragnatlis) in the two groups of arthropods, but Ligyda has a large median lobe, or ling~~a, which is not developed in Asellus, thus making it somewliat easier to compare all of the parts under consicleration, in the two groups of arthropods (insects and Crustacea), and on this account, Li,qyda, rather than -4sellus is here used for the pur- pose of comparison.
If the mderlip and maxi112 of the niayfly naiad are removed, as in Fig. 2, one may readily observe immediately behind, and between, the mandil~les id"^ a structure called the ,hypopharynx, which is coniposed of a median, tongue-like lobe, the lingua, "li", and a pair of lateral lobes, "pg", which the entomologists call CL superling~m", or parag gloss^" (a term which should be restricted to the outer lobes on either side of the gloss% of the labium). Similarly, in the crustacean shown in Fig. I, if the underlip and the two pairs of maxillz are removed) one may observe immecli- ately behind, and between, the mandildes, "mcY, a hypopharynx (exactly like that of the n~ayfly shown in Fig. 2) composed of a median, tong~~e-like ling~m~ "li", and a pair of lateral lobes, "pg", which the carcinologists call paragnaths. In the following disc~~s- sion, T have applied the carcinologists' term paragnaths, to the corresponding struct~~res in insects, and I have applied the ento- mologists' terms ling~~a and hyyopharynx to the corresponding structures in Crustacea, and allid arthropods. The absolutely patent correspondence hetween the parts of th~? hypopharynx of an insect (Fig. 2), and a crustacean (Fig. I), which is so simple and ~~tterly ol~vio~~s, that it should be evident to anyone possessed of even the rudiments of a knowledge of comparative anatomy, has apparently suffered through its very obviousness and simplicity, for the hunian mind is apt to regard the obvious with suspicion, as though it were a snare to entrap the careless or undiscriminating olxer~er, and to seek for subtler analogies which appeal more strongly to the imagination, and stimulate the speculative f acuities. The unmistakeable resem- blance between the hypopharynx of an insect (Fig. 2) and that of a crustacean (Fig. I), however, is not merely a superficial re-



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86 Psyche [June
semblance calculated to decei~~e the unwary2 since the hypopharynx in the two groups not only occupies the same position, and has the same form and str~~cture in both insects and Crustacea, but it also has exactly the same e~nbryological development, and serves the same f~~nction (i. e,, that of a secondary underlip, provided with taste organs, etc.) in both groups-and what, more could one ask, to establish complete homology ? I would therefore niaintai~~ that the so-called "superling~m" of insects do not represent th9 rnaxillul~ or first maxillz of Crustacea, since they do not occupj- exactly the same position, they do not exhibit the same form and structure, they do not have exactly the same en~bryological develop- ment, and they do not have exactly the same function in the two groups; and I would claim that the so-called "superlingua? of insects most emphatically do represent the paragnaths of Crus- tacea) since they agree with these in all of the features mentioned above.
Since the "superlingux? of insects represent the paragnaths of Crustacea, by comparing the higher Crustacea, which are near insects, with the lower Crustacea, which approach the trilobites and other primitive arthropods, we are able to trace the evolution of these structures, and to determine their morphological significance. In Ligyh (Fig. I) the paragnaths, "pg", are rather closely asso- ciated with the median lingua, "li)', which appears to be formed as a projection of the pharyngeal ridge, "pc)', behind it, which appar- ently includes in its composition a portion of the sterna of certain of the mouthpart segments. In Ta,Zorchestiu (Fig. 3) the lingu2, 46 li ,, , is represented by a double ridge) or lobe-like projection of the median pharyngeal ridge, "PC"; and it would appear that the median, basal portions of the paragnaths, "pg", likewise take part in the formation of the lingua) %", so that the lingua of higher Crustacea and insects may be formed in part by the paragnaths, although the greater part of the lingua is probably formed by por- tions of the sterna of certain of the mouthpart segments, as is indicated by embryology. On either side ~f the median pharyn- geal ridge, "pc", of Figs. I and 3, are rib-like structures, "tc", which are located at the base of the trophi or mouthpaits. It is possible that the lingual lor=, "11"~ of Figs. 2 and 8, represent



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19211 Crampton-flz~perlingum or Paragloss@ of Insects 87 modifications of these rib-like or ridge-like structures in insects, and it is also possible that certain of these structures may be the precursors of portions of the tentorium of insects? although I have not been able to determine this point as yet. The pharyngeal ridge, "PC", of Fig. 3? etc., appears to represent a portion of the sterna of the mouthpart segmentsJ which are quite broad in Fig. 4; and the lingua is not developed in the lower Crus- tacea. In Mysis (Fig. 4) the paragnaths, "pg", are borne at the anterior margin of the sternite, "m-rs"? of the first nlaxillary seg- ment; and in the lower Cr~~stacea? the paragnaths appear to bt: more closely associated with the maxillul~ or first maxillz? than they are with the mandibles, thus indicating that the paragnaths may represent detached lobes of the first maxill~. In Squilla (Fig. 61, the paragnaths, "pg"? are attached to the basal portions of the maxillul~ or first maxillz, "mx", and in the very primitive crustacean -4pzi.s (Fig. '7) both paragnaths, '(pg)', and maxillul~, "rnx''> arise from the same basal laminaJ "bl", which projects internally beneath the body wall. The paragnaths an4 maxillulze in Fig. 7 are bent over backward (instead of being repre- sented in their normal upright position, as in Fig. G), in order to show that both paragnaths and maxillulz are borne on the same basal lamina. The fact that both paragnaths and maxillulz arise from the same basal lamina in such primitive forms as Apus, would indicate that the paragnaths of higher Crustacea are merely de- tached lobes of the maxillulz, possibly corresponding to the endites or gnathobase-like structures of the trunk limbs of Apus; and in the higher Crustacea, these paragnathal lobes become more or less separated from the remainder of the first maxillz (maxillulix?), and become somewhat more closely associated with the mandibles, as a secondary modification.
I do not know of any instance in which the paragnaths are situ- ated in front of the mandibles, so that the metastoma, "mts") of the trilobite Trkrthms (Fig. lo), which is situated in front of the bases of the so-called mandibular appendages, '(md", (only the tips of the basal segments of these are shown in the figure) and occupies a position between the bases of the so-called second aii- tennz, "at", is situated too far forward in the head region, to



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88 Psyche [June
occ~~py a position strictly coniparable to that of the paragnaths, unless it be tr~~e that the so-called second antennze of trilobites, are in reality the representatives of the mandib~dar appendages of other arthropods. In certain trilobites there is a rather deep median incision, or elliargination in the inetastoma, thus suggest- ing that this organ may have been formed by the union of two lobes like the paragnaths; b ~ ~ t this cannot be demonstrated from the material at present available. The s~~ggestion that the nietas- tonia of trilobites niay represent the united paragnathal lobes of Crustacea, is thus merely a speculation, and has no particular bear- ing ~~pon the s~~bject of the origin and development of the parag- naths in Cr~~stacea and insects.
I imagine that there are still some individuals who will vigor- o~~sly maintain that the "superlingua? of insects must represent the maxillulz (first maxillz) of Crustacea, on the ground that Folsom, 1900, has described in a collenibolan embryo a supposed 6~ s~~perlingual" segment, or neuromere, which he claims is the rep- resentative of the first maxillary segment of Crustacea; and lie f~~rther claims that since the "superlinguze" are supposedly the appendages of this alleged "superlingual" segment, they must there- fore represent the maxillul~, or appendages of the corresponding first niaxillary segment, in Crustacea-
In reply to this argument, it is.suficient merely to call atten- tion to the fact that Philiptschenko? 1912 (Zeitschr. Wiss. Zoologic, Bcl. CIII)? who has made an exceptionally careful and thorough st~~dy of collembolan embryology, and has attempted to verify Fol- som's work on these insects (Bull. Haward 1811s. Comp. Zoology, 1900, 1701. 36, No. 5), has demonstrated that the supposed "super- Iing~~al" neuromere, or embryonic segment, described by Folsoix, exists only in its author's imagination; and recent writers who quote Folsom's mistaken obser~ations as tho~~gh they were estab- lished facts, are apparently wliolly ignorant of Philiptschenko's work? and know even less of the aii~~toniy and embryological devel- opment of the str~~ct~~res of Crustacea with which they seek to compare the struct~ire of insects. If there were no other reaso-iis for discrediting the statement that the '(superlingu& represent th maxillulz of Crustacea, the fact that the paragnaths (not the




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maxill~~lge) of Crustacea develop embryologically in exactly the same position and in the same vay as the "superlinguge" do in the embryos of insects, would be sufficient to completely disprove this unfounded and misleading statement, and it is hardly in keeping with the modern scientific spirit to continue to promulgate such misinformation, when a little time spent in the reading of the literature of the subject, or in easily conducted research, would readily convince anyone of its falsity.
Carpenter, 1903 (Proc. Eoyal' Irish Academy, Vol. 24, Section "B", Part A), interprets the structures labeled "a", "b", and "c", in Fig. 9, of the paragnath of Machilis inaritimii, as the repre- sentatives of the lacinia, galea, and palpus of the first maxilla (or "n~axill~ila") of a crustacean, in an effort to prove that the "superlinguse" (paragnaths) of insects represent the maxillulse of Crustacea. The structures which he figures in the ('s~~perliiigua" of Xachilis, however, are nothing like the true lacinia, galea, and palpus of the maxillulse themselves, in Crustacea, but are exactly like similar structures found in the paragnaths of Crustacea, as one would expect to be the case if the "superling~~se" of Machilis represent the paragnaths, not the maxillulse, of Crustacea. Liter- ally hundreds of Crustacea exhibit in their paragnaths small pro- jections like those labeled '(a" and 'V in Fig. 9; and these pro- jections of the paragnaths of Crustacea not only have the same appearance as these structures in the "superlingua" of Machilis, but they also bear the same type of hairs, taste organs, etc., as in Madiilis. Furthermore (as I have pointed out in several papers), the palpus of a maxilla of an insect, or crustacean, represents the terminal segments of a mouthpart limb (the endopodite) in which the basal segments form the body of the maxilla, the galea and lacinia being appendages (endites, or gnathobase-like structures) of the basal segments of the maxillary limb. Since the palp~s represents the terminal segments of such a modified limb, and since the ^superlinguse" (paragnaths) do not represent modified limbs, they cannot possibly have a palpus; and the small outgrowth labeled "c" in Fig. 9 of the paragnath ('(s~iperlingua") of Machili^, is merely a small, secondarily formed appendage, similar in nature to the articulated appendage "c", borne on the paragnath of the



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90 Psyche [June
crustacean shown in Fig. 5.
I11 Fig. 14, Plate 11, of a paper on
Anurida (L.M. B. C. Memoir No. XJII), an appendage of this kind, borne near the tip of the paragnaths as in Apseudes (Fig. 5), is figured in the "niaxillula^ (i. e. the true paragnaths) of the insect Anurida, by Imrris, 1906; and in both insects and Crustacea, these appendages of the paragnaths cannot possibly be homologized with the palpus, or terminal segments of the endopodite of the limb forming the ma~illula, or first maxilla. The principal points brought out in the foregoing discussion may be briefly summarized as follows. The great similarity between the hypopharynx of insects and Crustacea lends additional weight to the evidence of a very close relationship between these two groups of arthropods, furnished by a study of numerous other structures of the body as well; and since no such close correspondence in the details of the parts of insects and chilopods exists, it is infinitely more probable that insects were descended from crustacean-like (instead of chilopod-like) ancestors. The "superlinguae" of insects, are completely homologous with the paragnaths of Crustacea, be- cause they occupy exactly the same position, and have the same form structure, and function in the adult condition, and arise in the same location, and in the same fashion, during embryonic developnlent in both groups of arthropods, thus fulfilling all the requirements for establishing complete homology between the cor- responding parts in insects and Cr~st~acea. Since the paragnaths
of Crustacea are not the maxillulae of Crustacea, it is folly to state that the "superlinguse" of insects correspond to the maxillulse of Crustacea, if they represent the paragnaths of Crustacea instead; and it is to be hoped that if anyone is unwilling or unable to inform himself as to the truth in this matter, that he will at least refrain from deceiving others by promulgating the misinformation that the "superlinguse" of insect.^ represent the maxillulse of Crustacea,. as though it were a demonstrated fact!
EXPLANATION OF PLATE V.
Fig. 1. Posterior (ventral) view of mandibles and hypopharynx of the crustacean Ligyda.
Fig. 2. Same of a nymph of the mayfly Heptagenia. The hypoporus, or salivary pore beneath
the hypopharynx is not shown.
Fig. 3. Posterior (ventral) view of the hypopharynx of the crustacean. Talorchestia.
Fig. 4. Ventral (posterior) view of the sternum of the first maxillary seg- ment, and the paragnaths of the crustacean Mysis.



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PSYCHE, 1921.
VOL. XXVIII, PLATE V.
C~~~~~ol~~~Superlinguce or Puraglossos of Insects.



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92 Psyche [June
Fig. 5. Posterior (ventral) view of the paragnaths of the crustacean Apseudes.
Fig. 6.
Posterior (ventral) view of a paragnath and maxillula of the crus- tacean Sq u i l l a.
Fig. 7.
Anterior
(dorsal) view of a paragnath and maxillula of the crus- tacean Apus, bent over backward to show attachment to the basal lamina. Fig. 8. Ventral (posterior) view of a paragnath and the lingua of the insect Machilis.
Fig. 9. Same view of a paragnath of Machilis taken from a drawing by Carpenter.
Fig. 10. Anterior view of motastoma of the trilobite Triarthrus from a drawing by Raymond.
Abbreviations.
a, Lobule of paragnath;
at, Portion of basal segment of trilobitan limb hoinologized with second antenna; b, Lobule of paragnath; bl, basilamina, or basal lamina which bears the paragnath and maxillula; bp, BasiparagnaLh, or basal portion of paragnath; c, Epiparagnath, or appendage of paragnath; dp, Distiparagnath, or distal portion of paragnath; li, Lingua; 11, Lingua- lora, or lora of lingua; md, Mandibles; mts, Metastoma of trilobite; mx, First maxilla, or maxillula; mxs, Sternum of first maxillary segment; pg, Paragnaths, "superlinguse"', or "paragossse"; pc, Pharyngocrista, or median pharyngeal ridge; tc, Trophicostse, or rib-like structure at bases of trophi.
PROCEEDINGS OF THE CAMBRIDGE ENTOMOLOGICAL CLUB.
At the meeting of February 8, Prof. W. M. Wheeler described. the nesting habits of some ants of the genus Carel)c~ru, found in South America. These live in nests of Termites, making their ow11 burrows between those of their hosts and feeding on the young of the latter. The various forms of these ants had been obtained from the stomachs of Anteaters killed near their nests. The males and females wer'e of large size and the workers extremely small. When the males and females leave the nest for the mating flights some of these minute workers cling to their hairs, and when the females start new colonies these workers bring in food and feed the first-hatched young, which the female herself is unable to do. Another geirus of ants of small size, AUonzer'~/s, lives partly i-n the swoollen branches of certain plants, going up and down between the plant 'and the underground nest in earth-covered galleries attached to the hairs of the plant.
Prof. C. T. Brnes described some gnests of Ants and Termites from South America.
Vingless flies of the family Phoridcv live in the nests of some ants and even travel with them in their raids outside the nest.
In some termite nests are minute hymenopter-



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