G. C. Wheeler.
The Larva of Leptanilla (Hymenoptera: Formicidae).
Psyche 35(2):85-91, 1928.

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19281 The Larva of Leptanilla 85
THE LARVA OF LEPTANILLA (HYM. : FORMICIDX) University of North Dakota
Leptanilla revelierei sardoa Emery
Larva:Body long, slender ,subcylindrical, or t'hocephalic and straight except for the thorax which is slightly curved ventrally; with eleven distinct postcephalic segments. Diameter greatest at the sixth abdominal segment; decreasing slightly toward the posterior end which is rounded and terminates in a small hemis- spherical boss; and diminishing progressively to the anterior end, except for a slight constriction at the first abdominal seg- ment. Relative diameters of the segments (beginning with the prothorax as the unit) : 1.00-1.30-1.50-1.45-1.80-2.00-2.45- 2.80-3.00-2.95-2.75. Relative lengths of segments: 1.0-1.9- 3.4-3.1-3.6-4.0-5.3-4.0-3.7-3.3-7.7. (Fig. 1A) Projecting downward and forward from the ventral side of the prothorax there is a curious structure suggestive of a plow- share. This is furnished with three hairs: a short, simple, slightly curved seta arising just back of the apex on the ventral side, and two longer pendulous hairs, which are curved at their distal ends and bifid at the tips, arising dorsolaterally just back of the middle of the structure.
(Fig. 1B and E)
On either side of the fourth abdominal segment near the posterior border there is a bare circular area enclosted by a narrow heavily chitinized band, the whole structure (provisional- ly called "tympanum") being about 0.037 mm. in diameter. It is bordered by a fringe of stiff hairs, which are stouter and a trifle longer than those on the adjacent integument; there are also a few of these on the heavily chitinized band. Attached to the bare area near its posterior margin is an internal tube-like structure; this is twice bent and its diameter increases toward the inner end; its length is about 0.06 mm. (Fig. ID) 'Contribution from the Zoological Laboratory of the College of Liberal Arts at Syracuse University.
Pu&e 35:85-ill (1928). hup ttpsychu einclub orgtlS/lS-085 html



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86 Psyche [Itm
Hairs of four types: (a) Minute, thin, somewhat flexuous hairs (length 0.01-0.03 mm.), which form a rather dense covering for the entire body, except the head, prothorax, "tym- panum)" and caudal boss; these are arranged in transverse rows encircling the body; they are spaced at distances roughly equal to their length, which is least at the anterior end and greatest at the posterior. (b) A few short, stout, rather stiff hairs, irregularly distributed and ranging in length from 0.02 mm. on the prothorax to 0.08 mm. on the last abdominal seg- Fig. 1.-Larva of Leptanilla wvelierei sardoa Emery: A, in profile, X60;,,B, head and prothorax in profile, X410' C
cephalk aspect of head X400" D, "tympanum, dorsal vim,
X580; E. cephalic aspect of'plkvshare-1'ke organ on pro<h;rax. '~425. ment.
(c) Long hairs with rather flexuous tips arranged sym- metrically in pairs on the dorsal surface, one pair each on the second to seventh (inclusive) abdominal segments; varying in length from 0.13 mm. to 0.16 mm. ; four of the longest forming a ring around the base of the caudal boss. Just outside this ring there are attached (d) two extremely long (0.3 mm.) hairs; these six hairs converge apically and give the appearance of a caudal appendage.




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19281 The Larva of Leptanilla 87
Head (Fig. 1C) minute, naked, its outline pyriform when viewed from in front, twice as long as its greatest breadth (which is one-fourth of its length from the occipital border), narrowed at the base of the mouth-parts, with the occipital border broadly rounded. Antenna1 rudiments situated one-third of the length of the head from occipital border; long, narrow and apparently adnate to the head. Tentorium (?) conspicuous, in the form of ,
a long, narrow, median bar, which is abruptly widened at the posterior end and furcate anteriorly, each division leading to- ward the base of a mandible.
Labrum semicircular, the margin finely undate, the basal angles produced outside the mandibles into stubby flaps which are toothed on their anterior and distal borders (Fig. 15). Mandibles long, slender, slightly curved, acute, simple, feebly chitinized and directed downward and somewhat backwards along the sides of the labium. Maxillae lobiform, each with three sensillse. Labium narrowed at the base, broader at the distal border, which is smooth and slightly curved; with lobiform sense-organs at the anterior corners, each with three sensillse; opening of sericteries not evident. Trophorhinium wanting. This description is based on three larvae, which have been cleared in potassium hydroxide (10%)) stained with acid fuchsin, and mounted in balsam on slides. They are labeled "Sardegna: Golfo Aranci. I. 1909 A. Dodero."
I am indebted to Dr. Rafaelo Gestro of theMuseo Civico di Storia Naturale of Genoa, thru the kindness of Dr. W. M. Wheeler, for this material.
The genus Leptanilla has always been more or less incertoe sedis. Emery, when he established it in 1870, placed it in the "Dorylidse" near Typhlopone. Mayr, however, in a letter to Emery (date not given-see Emery 1904) dissented, maintaining that it belonged with the Myrmicinse. Emery was evidently convinced, for in 1875 he removed it to the "Mirmicidei" in the neighborhood Stenamma and Liomyrmex. In 1877 he moved it to the vicinity of Monomorium and Leptothorax in the "Myrmici- dei genuini" but marked it with a query to signify uncertain position. In 1881 Ern. Andre had it in the first tribe, "Myrmi-



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88 Psyche
cidse verse," of the "Myrmicidse" but
with the "Dorylides."
[June
mentioned its affinities
Fore1 in 1893 did not mention the genus but might have meant to include it in the subfamily Myrmicinse, when he said that the fourth tribe (('Myrmicii") included "les autres genres de la sous-famille des Myrmicinse." And later (1901) he excludes it from the Dorylinse when he says, "Done, je maintiens la sous- f amille Dory line limit 6e aux genres Dorylus, A enictus, Eciton et Cheliomyrmex." In von Dalla Torre's "Catalogus" (1893) it was still in the Myrmicinse but near Trigonogaster and Pheidolo- geton. In 1895 Emery was still of the opinion that it belonged in the subfamily "Myrmi~ini'~ in the second tribe ('(Myrmicii7') near Huberia and Phacota. But nine years later (1904)) after describing the female of L. revelierei Emery, he returned it to its original subfamily (Dorylinse). In the following year, however, in Ashmead7s skeleton it stood between "?Li~myrmex'~ and Epi- pheidole in the tribe Stenammini, subfamily "Myrmicinse," family "Myrmicidse". In 1907 Santschi described males of three species, which he referred to the Genus Leptanilla and claimed that their doryline affinities justified Emery's original allocation of the genus. It should be noted, however, that males of Leptanilla have never been taken with females or work- ers; hence it is not certain that those described by Santschi belong to this genus. In the "Genera Insectorurn" (1910) Emery established for the genus a separate tribe (Leptanillini) in the subfamily Dorylinse, where it seemed destined to abide in isola- tion; Wheeler (19 10: "Tribe Leptanillii"), Fore1 (1917), and Fore1 (1921: tribe not given), and Wheeler (1922) have not dis- turbed it. But recently Wheeler (1923) has suggested that even further isolation may be necessary:
.
"Most myrmecologists recognize only five subfamilies of ants and regard the Cerapachyinse as belonging to the Ponerinse, the Pseudomyrminse to the Myrmicinse. It is probable, how- ever, that future myrmecologists will increase the number of subfamilies. I believe that the tribe Leptanillini, which Emery includes among the Dorylinse, will have to be separated out as a distinct subfamily (Leptanillinse). Dr. George C. Wheeler



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19281 The Larva of Leptanilla 89
finds that the larva of Leptanilla is very aberrant, and the characters of the adult are either quite unlike those of other Dorylinae or only superficially similar and due to convergence, or similarity of subterranean habits." (page 335) The larva of Leptanilla does bear certain resemblances to the known doryline larvae (Dorylus, Aenictus, Eciton, Chelio- -ex) : the long, slender, subcylindrical, orthocephalic, nearly straight body, narrowed progressively from behind forward; the small, feebly chitinized mandibles; the absence of a tropho- rhinium on the mouth-parts. On the other hand, it differs in the constriction at the first abdominal segment; the long hairs on the abdomen, especially the extremely long pair at the posterior end; the absence of hairs on the head; the shape of the head, which in the~or~linae is suborbicular. But these differences become trivial and insignificant beside the four which not only differentiate it from the Dorylinae, but also from all other known formicid larvae (130 genera). Leptanilla is unique in the (1) possession of the plowshare-like structure on the ventral side of the prothorax, (2) the "tympanum" on either side of the fourth abdominal segment and (3) the toothed flaps of the labrum and (4) in the position of the mandibles, which are directed down- ward and somewhat backward along the sides of the labium instead of lying across the front of the labium with their apices nearly touching or crossed.
These aberrant characters of the larva of Leptanilla support the contention of Dr. W. M. Wheeler (quoted above) that the tribe Leptanillini should be removed from the Dorylinee and raised to the rank of a subfamily.
Concerning the functions of these peculiar structures nothing is known. The plowshare-like structure on the prothorax might be an exudatorium; the "tympanum" suggests an auditory organ. If the larvae of this rare ant (or of any related species) are ever collected again, they should be kept alive in an artificial formicary and studied for the purpose of solving these problems. Also some specimens should be suitably killed and fixed for histological examination.
It is interesting in this connection to note that another



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90 Psyche [June
formicid subfamily has been based partly upon larval characters, namely, the Pseudomyrminse established by Emery in 1899. It is now known that the characters he used (hypocephaly and the presence of antenna1 rudiments) are not distinctive. Valid characters were found, however, by Wheeler and Bailey (1920) in their study of the larvae of Pseudomyrma, Tetraponera, Pachy- sirna, and Viticicola: the straight cylindrical body and the tro- phothylax. And Wheeler (1920, 1922, 1923) has since recognized the group as a distinct subfamily.
Literature Cited.
Andre, Ern.
1881-1882. Species des hyn16nopt6res composant le groupe des formicides d7Europe, etc.
Gray, pis. 1-25, 8 suppl.
Ashmead, W. H.
1905.
A skeleton of a new arrangement of the families, subfamilies, tribes and genera of the ants, or the super- family Formicoidea. Canad. Ent. 37 : 381-384. von Dalla Torre, K. W.
1893. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus. Vol. VII : Formicidae (Heterogyna) . viii, 289, Leipzig.
Emery, C.
1870. Studi myrmecologici.
Boll. Soc. Ent. Ital. 2: 9 p.,1 pi.
1875. Le formiche ipogee, con descrizione de specie nuove e poco note. Ann. Mus. Civ. Genoa 7: 465-474, 1 fig. 1877. Saggio di un ordinamento naturale dei myrmicidei e considerazioni sulla filogenesi delle formiche. Boll. Soc. Ent. Ital. 9: 1-17, 1 pi.
1895.
Die Gattung Dorylus Fabr. und die systematische Eintheilung der Formiciden.
Zool. Jahrb. Abt. Syst. 8:
685-778, 3 pi., 41 fig.
1899.
Intorno alle larvae di alcune formiche. Mem. Accad Sc. Bologna(5),8:3-10,2pl.
1904. Le affinity del genere Leptanilla e i limiti delle Dory- linse. Arch. Zool. Napoli 2: 107-116, 9 fig.



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19281 The Larva of Leptanilla 91
1910.
Family Formicidee, Subfamily Dorylinse in Wyts- man's "Genera Insectorum."
Fascicle 102, 34 p , 8 fig., 1
PI.
Forel, A.
1893. Sur la classification de la famille des formicides, avec remarques synonymiques. Ann. Soc. Ent. Belg. 37 : 161- 167.
1901. A propos de la classification des formicides. Ann. Soc. Ent. Belgique. 45: 136-141.
1917. Cadre synoptique actuel de la faune universelle des fourmis.
Bull. Soc. Vaud. Sc. Nat. 51: 229-253
1921. Le monde social des fourmis du globe. Vol. I. xiv, 192, 3 pi., 30 fig. Geneva, Librairie Kundig. Mayr, G.
1877.
Ueber Dr. Emery's Gruppierung des Myrmiciden. Sitzb. Zo01.-bot. Gesell. Wien 27 : 23-26. Santschi, F.
1907. Fourmis de Tunisie capturees en 1906. Rev. Suisse Zool. 15, 2: 305-334.
Wheeler, W. M.
1910.
Ants: Their structure, development and behavior. xxv, 663, 286 fig. New York, Columbia University Press.
1920.
The Subfamilies of Formicidse, and other taxonomic notes.
Psyche 27: 46-55, 3 fig.
1922. Ants of the American Museum Congo Expedition. A contribution to the myrmecology of Africa. Bull. Amer. Mus. Nat. Hist. 45: 1-1139, 103 fig., 47 maps, 45 pi. 1923. Social life among the insects. Being a series of lectures delivered at the Lowell Institute in Boston in March 1922. vii, 375, 116 fig. New York, Harcourt, Brace and Company, Inc.
Wheeler W. M. and Bailey, I. W,
1920. The feeding habits of the Pseudomyrininse and other ants.
Trans. American Phil. Soc., Art. 4, 237-278, 6 fig., 5 pi.




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