140 
Psyche 
[December 
of the Ichneumonoidea.” Keilin 2 has found comparable 
structures on the apterous larvae of many families of 
Diptera. He calls them organes sensoriels vestigiaux des 
pattes. They are always in the same position on the thoracic 
segments and they always consist of three or four sensory 
hairs, which are sometimes mounted on small protuberances. 
Keilin concludes that they are vestigial legs because of their 
general occurrence throughout the Diptera; because of the 
constancy of their form and constitution ; because they are 
found exclusively on the ventral surface of the thoracic seg- 
ments ; and finally because of their relations to the imaginal 
buds. This conclusion is in accord with that of Perez. 3 
Among the ant larvae these leg vestiges attain their maxi- 
mum size in the army ants (Dorylinae). In the genera 
Dorylus, Eciton, and Cheliomyrmex they are relatively large, 
subcircular, convex, slightly elevated papillae. In the mature 
larvae of Eciton hamatum (Fabr.) (Fig. 1) and Dorylus 
(Anomma) wilverthi Emery the diameter of the papilla is 
0.05 mm. This is also the size in both young (?) larva 
(2.8 mm. long) and a mature larva (5 mm. long) of 
Cheliomyrmex megalonyx Wheeler. I can find nothing to 
suggest a sensory function. In E . hamatum the surface of 
the papilla is roughened, but in the other two species it is 
apparently quite smooth. The close relationship between 
vestigal legs and imaginal buds is shown in Figs. 2, 3, and 5. 
In some genera of other subfamilies the vestiges are small 
transversely elliptical papillae, but more commonly they 
appear merely as short transverse lines (grooves or ridges?) 
which are often difficult to find (Fig. 11) . In some genera I 
have found no trace of the vestiges ( e.g ., Eusphinctus stein- 
heili Forel and Lioponera luzuriagae Wheeler & Chapman). 
It is not surprising that these vestigial legs have been 
overlooked in ant larvae, for in addition to being minute and 
inconspicuous (except in the Dorylinae), it is very difficult 
to distinguish them except in exoskeletons cleaned with a 
solution of potassium hydroxide and stained with acid 
fuchsin. 
In addition to the vestigial legs I have found some other 
puzzling structures in ant larvae. On the mesothorax and 
2 Keilin, D. 1915. Bull. Soc. France Belgique. 49: 166-173. 
3 Perez, C. 1911. C. R. Soc. Biol., Paris. 71: 498-501. 
