William Morton Wheeler.
An Anomalous Blind Worker Ant.
Psyche 23(5):143-145, 1916.

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19161 Wheeler~An Anomalous Blind Worker Ant 143 the ants you sent me with F. Smith's types (two workers on one card, one large, one medium) of Solenopsis soevissima at the British Museum on Saturday and they agree perfectly in every way. The types were taken by H. W. Bates at Para." There can be no doubt, therefore, that Forel's pylades is merely a synonym of scevissima Smith.
Forel disagrees with me further on the rank of this form, main- taining that it should be regarded as a distinct species and not as a subspecies of geminata, because the polymorphism of the worker is very feeble, owing to the complete absence in the colonies of any large-headed forms like those of geminata. This is a matter of personal opinion. I called attention to the fact that two of our North American forms, maniosa Wheeler and xyloni Mac- Cook are in this respect intermediate between scevissima and gemi- nata, and I may add that the Brazilian form medusa, recently described by Mann, is even more polymorphic than geminata since its largest workers have the head greatly enlarged and flaring in front, with very strongly curved mandibles. If scevissima is ele- vated to specific rank, these forms should also have the same status, but in my opinion they may all be regarded as so many subspecies of a single variable species. I admit that it might be more logical to include aurea Wheeler as still another subspecies, with ambly- chila Wheeler as its variety. Owing to the great accumulation of forms in this section of the genus Solenopsis within recent years I am not altogether averse to regarding soevissima,.geminata, maniosa xyloni, electra, medusa and aurea as so many different, though very closely allied, species.
AN ANOMALOUS BLIND WORKER ANT.
Several years ago Prof. C. F. Baker sent me from Catalina Island, Calif., a number of ants which I described as Aphce- noqaster patruelis Forel var. bakeri. Later he gave me a vial of additional specimens from the same colony. While mounting these I detected among them a single eyeless worker, which seemed to be worth describing and figuring as, to my knowedge, nothing like it has been seen in the genus Aphanogaster nor, indeed, in any



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144 Psyche [October
other genus of ants possessing well-developed eyes in the normal workers. The workers of Aphoenogaster bakeri, like those of all the species of the genus, are monomorphic or very feebly poly- morphic, and the eyes, though not large, are nevertheless well developed. The exceptional specimen is in all respects normal except in the shape of the head and the absence of visual organs. '-Ìö,
-4 -a. Head of normal worker of Aphoenogaster patruelis Fore1 var. bakeri Wheeler.
b. Head of eyeless worker of
same.
The head, as will be seen from a comparison of the figures, is sub- oblong and the sides, especially at the middle, are very distinctly concave, probably owing to an absence of the optic ganglia. On the left side the integument, where the eye should be, is slightly rugose and presents what appears to be a single minute, pigmented ommatidium; on the right side the integument in the correspond- ing concavity is smooth and rather pale. That the eyeless indi- vidual had been living and working for some time like its normal sisters is shown by its mature coloration and the blunted teeth of its mandibles.
As colonies of Aphcenogaster contain, as a rule, only a single fertile queen, it is very probable that the anomalous specimen above described and the normal workers are all daughters of the same mother. We may, therefore, assume that the eyeless worker is a mutation, strictly comparable with the eyeless specimens that have appeared in certain cultures of the fly Drosophila, and we might infer that the normally eyeless workers and females of such ant genera as Dorylus and the corresponding phases of certain species of Eciton, in which the eye is reduced to a single omma- tidium, arose as similar mutations. We might be tempted, more- over, to extend this inference to other peculiarities of worker ants,



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19161 Wheeler-An Anomalous Blind Worker Ant 145 since many such peculiarities are merely suppressions or absences of structures that are well developed in the males and females of the same species. I doubt, however, whether we are justified in drawing such a sweeping conclusion in the face of numerous facts which indicate even more forcibly that the worker characters have arisen from continuous and fluctuating variations. In many genera of ants with polymorphic workers (Camponotus Pheidole, etc.) and in many genera containing numerous species, though with monomorphic workers (Solenopsis, Monomorium, etc.) the eyes show a gradual or serial diminution. Discontinuity may, therefore, be conceived to arise in the development of these struc- tures by a selective survival of certain stages or phases, just as it does in the series of species or of dimorphic workers of the same species. The absence of wings is another character in worker ants which is sometimes supposed to have arisen as a mutation, but, though very rare, anomalous workers with vestigial wings (pterergates) are known t,o occur. I have recorded and figured such cases in Myrmica and Cryptocerus, and others have been ob- served in the former genus by Wasmann and Donisthorpe. Recently I have found an even more instructive case, an Australian Monomorium, allied to M. rothsteini Forel, the normal females of which have very small wings, too small to be of any service as organs of flight. These females, which will be described and fig- ured in a future paper, are, in fact, truly brachypterous, like cer- tain well-known species of Diptera, parasitic Hymenoptera, Hete- roptera and Orthoptera, and suggest that the complete loss of wings in the worker is merely the final stage in a gradual diminu- tion of these organs and has, therefore, originated from continuous variations. As the worker phase of the ants must have been per- fected and fixed as a family character not later than the Eocene Tertiary and probably as early as the Cretaceous, it is not sur- prising that at the present time organs characterizing stages inter- mediate between the workers and females should be so rarely resuscitated as anomalies.




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