W. S. Creighton.
Notes on Three Abnormal Ants.
Psyche 35(1):51-55, 1928.

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19281
Notes on ihree Abnormal Ants
NOTES ON THREE ABNORMAL ANTS.
Abnormalities in ants appear to fall into three fairly well defined categoriesl viz.: (1) sex mosaics and intersexes) (2) aberrant forms produced through altered food supply, (3) freaks. To the first group belong the various kinds of lateral mosaics as well as the rarer anterio-posterior type. The latter oft>en show characteristics which mark them as intersexes rather than t.rue mosaics. The second group is composed of a large number of peculiar forms which arise from pronounced nutritional irregu- larities. Lack of food may produce dwarf individuals in all three castes) while loss of food due to the presence of parasites gives rise to pseudogynes or the shriveled victims of Orusema. In the event of an overabundance of food unusually large males and femalesl egg-laying workers andl more rarely, repletes may result. It is impossible to draw any hard and fast line between the mem- bers of this group and those forms considered normal since in many cases conditions which originally must have been quite aberrant havel in timel become an integral part of the life of the species (e. g. the repletes of Myrmecocystus or the microgynes of certain Formicas). In the third group may be included those in- dividuals which show duplication1 loss or malformation of parts. Most of these conditions seem to be due to injuries in the larval or pupal stages, More rarely the changes are of an atavistic nature.
Many of the members of this group are veritable en- tomological nightmares? monstrosities with double scapes or legs; fantastic creatures with shortened and twisted antennz and limbs or misshappen thoraces; freaks without eyes, or Iack- ing tarsal, antemall rarely even petiolar joints. In this paper are described three abnormal ants, two freaks and an ergatandromorph. Both freaks are in the collection of Dr. Wheeler through whose kindness I am enabled to describe them. It is therefore my pleasure to thank the donors for their 1Contributions from the Entomological Laboratoq of the Bussey Tnsti- tution, Harvard Univer&y, No. 291.




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52 Psyche [MW~
contributions.
The first of these) a queen of Monomorium mini- mum Em. which lacks the left eye) was taken at Urbana) Ill. by Mr. M. R. Smith. Plate. 1, Fig. 4 shows the head of the insect. The asymetry caused by the absence of the left eye is further increased by a narrowing of the same side of the head. The left half is very little more than half the width of the right except just behind the mandible where it suddenly flares out to full width. The left ocellus is misshappen and displaced. Dr. P. W. Whiting informs me that similarly deficient individuals occasionally arise in his Habrobracon stocks, and when) as more rarely happens) both eyes are absent, extreme microcephaly results. No dissection was made of the insect here described but it seems likely that the greater portion of the left optic tract is absent. The cross sectional area of the mandibular muscles must also be greatly reduced. In all other regards the specimen ap- pears to be perfectly normal.
The second abnormality is a dealated queen of Myrmica scabrinodis var. (probably sabuleti Mein.) which lacks both petiole and post petiole. This astonishing insect was found by Miss H. Andrews at Boulder, Colo. in 1916. Figs. 5 and 6 show the thorax and abdomen in profile and from above. The thorax is joined directly to the gaster) the two petiolar joints having fused with the anterior face of the first gastric segment. The joints are broadened and flattened past recognition) forming a fan-shaped area on the gaster, Nevertheless their nature is strikingly apparent because of their characteristic rugose sculp- ture and lighter color. On the right side of the gaster close to the fused nodes is a small tubercle, It has no apparent connec- tion with them nor any obvious significance. At least two similar abnorn~alities have been previously described. Donis- thorpe) in 1922) published a short paper containing an account of a dealated queen of Leptothorax acervorum F. which lacks the petiolar joints. The altered condition of this insect he considers an atavism. In 1927 Karajew described an aberrant worker of fWegaponera j~tens F. in which the petiole is absent. Unfor- tunately the insect was not figured but the author notes that* in other respects it was normal.
The last specimen to be dealt with in this paper is an ergat-



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19281 Notes on three Abnormal Anis 53
andromorph which I took in the summer of 1927 at Boulder, Colorado. On August 10th while collecting along the foot of the ridge between Gregory and Bluebell Canyons, I found a nest of Formica nitidiventris, Em. containing an ant with wings on the left side only. The insect was in the upper galleries of the nest in the company of twenty or thirty workers. The latter fled as soon as the covering stone was raised) leaving the ergatandro- morph whose slower movements hindered its escape. When allowed to walk on a relatively smooth surface it circled to the right.
Fig. 1 shows the more important features. The left half of the insect is male) the right worker, although in the head and thorax the junction does not occur at the mid-line of the body. The structures of the opposite sides of the head appear to be quite typical as regards their respective castes. The right (worker) antenna has the requisite twelve joints of the customary shape and size. The right eye and mandible differ in no way from those of the normal worker. On the left (male) side the eye is much larger) the mandible greatly reduced and the antenna of thirteen joints, all usual male features. The clypeus is twisted to the left, a result of the obvious discrepancy in the length of the gene (Fig. 2.) Aside from the major structural differences in the males and workers of this subspecies there are certain pecularities of color and pilosity characteristic of each. Thus the head and thorax of the normal worker are a rufous brown and those of the male a deep brownish black. In Figs. 1 and 2 this darker male coloration has been indicated by stippling. Referring to 2 ib may be seen that the entire clypeus and most of the vertex and occiput are of worker origin. There is also a curious projection of worker tissue which runs downward from the vertex to the upper border of the eye. All three ocelli occur in worker 'tissue and all are of the small size characteristic of the worker.
Taking into consideration the radical differences in the thoracic
structured of the male and worker the thorax of the mosaic is less mixed than would appear at first sight. The pro- thorax of the worker has fused fairly evenly with the pronoturn of the male. The mesothorax is united with the scutum, the



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54 Psyche arch
parapsis and the scutellum. The small metanotum of the male isdapparently free throughout the greater part of its length. It lies in a deep suture which extends entirely across the thorax. The last portion of the thorax appears to be intermediate in structure between the metathorax of the worker and the epino- tum of the male. Its color would indicate worker tissue but its structure is not that of the typical worker metathorax. Both wings are present on the left side of the insect and both are fully developed. The petiole is cleanly divided along the mid- line of the body. The right half is higher and broader than the left and has an acute upper edge. The upper edge of the left half is obtuse and the coloration is a blackish brown. The differences in the shape of the opposite halves of the abdominal segments cause a pronounced asymetry of the gaster. Since the gastric segments of the normal male are of nearly uni- form length throughout) while those of the worker successively decrease in length after the second segment) their combination has resulted in a strong bending of the tip of the gaster towards the right. This bending has affected the male genital armature. All the elements in the left half of the male genetalia are present and individually quite normalz. Their relative positions) how- ever, have been somewhat altered.
In the normal male the
stipites are outermost in position. Just within and closely ap- pressed to each of these is a bifurcate organ composed of an outer) hooked volcella and an inner) foliate lacinia. Innermost
of all and somewhat above the rest are the paired inner para- mera. In addition there are present two small lobed structures, the cerci. Ordinarily these lie just above the median lobes and .are partially covered by the sixth gastric segment. They are
apparently not a part of the genetalia and are mentioned here only because a single aberrant cercus occurs in the gynandro- morph. Fig. 3. shows the position of the male genital armature in the mosaic. The stipes (s) has been turned inward toward the center so that it occupies a position above the volcella (v) and 2Emery's nomenclature is here used. For a discussion of the names ap- plied to the structures of the Formicid genetalia see Emery, Die Gattung Dorylus. Mol. Jahrb Band 8 1895.




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19281 Notes on three Abnormal Anb 55
lacinia (1) and the inner paramer (p). The ends of these may be seen projecting to the right of the stipes. Above the stipes is the sixth gastric segment of the male. Near the base of the stipes is the small, club-shaped cercus (c)., It is entirely exposed and borne on a small extruded portion of unchitinized tissue. The very characteristic circular, hair-fringed anal aperture of the worker, if present) is distorted past recogni- tion.
The legs of the two halves of the mosaic are normal for male and worker respectively. Those of the male side are darker and somewhat more curved than their opposites. Measurements
show them to be slightly shorter. The figure cannot be used in this connection since no attempt was made to draw opposite appendages in similar positions. The difference in length is such that one would expect the insect to circle gradually to the left when walking. Actually, as has been noted) it circled sharply to the right, a result probably due to the distortion of muscles in the thorax,
Lifierafiure Cited.
Donisthorpe? H. 1922. On some Abnormalities in Ants. The Entomologists Record? Vol. XXXIV., No. 5. Karawajew) W. 1927. Ein Fall von lateralem Hemaphroditisd mus bei Ameisen und ein Fall defekter Korperbildung. Folia Myrmecologica et Termitologica Vol. I R. 4-5.



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