Dec, 1908.] Wheeler: Studies on Myrmecophiles. 209 



The more dorsal fringe consists of very delicate, short, curly hairs, 

 while the ventral fringe is borne on a diaphanous striated lamina and 

 is made up of flattened hairs, with long, slender, flexuous tips. The 

 anterior border of the body is distinctly notched in the middle. The 

 posterior tubercle is very long (1.7 mm.), with a ring-like groove 

 around its base, and terminates in a pair of short blunt processes, each 

 of which bears one of the anal stigmata. The whole surface of the 

 tubercle is somewhat shining and finely rugulose. 



The puparium measures 11 mm. It is smoother, more convex 

 and somewhat darker brown than the larva. The anterior tubercles 

 seem to be replaced by a pair of large, broadly elliptical discs or 

 spots, representing less heavily chitinized areas of the puparial wall. 



Larvae and puparia of this description were found in a nest of F. 

 fusca var. subsericea at Fort Lee, X. J., during April. I have some 

 larvae also from two localities in Massachusetts, collected in nests of 

 the same ant by Mr. A. P. Morse and Mr. A. C. Burrill, and there are 

 in the Museum of Comparative Zoology several specimens taken in the 

 same state by Mr. E. A. Samuels. 



We may conclude from the foregoing account that the typical and 

 most frequent hosts of Microdon in the north temperate zone are the 

 species of Formica. In tropical and subtropical regions, however, 

 where this genus of ants is absent, the hosts belong to different and 

 often to very diverse genera. Wasmann (1894) mentions Camponotus 

 hildebrandti as the host of a Microdon in Madagascar. I have given 

 an account (1901) of the larva of another undetermined species from 

 the nest of Pseudomyrma mexicana, one of the fiercest of our American 

 ants, and Brues (1903) has described and figured a very peculiar 

 puparium, which probably belongs to a genus allied to Microdon and 

 was taken in California by Prof. H. Heath in the nest of a very small 

 black Myrmicineant, Monomorium minutum Mayr. I find no mention 

 of the species of ants with which the other recorded tropical and sub- 

 tropical Microdons have been taken. We should expect the Australian 

 forms to occur in the nests of Iridomyrmex species, the South African 

 forms with the larger species of Plagiolepis. 



The relations of Microdon to its hosts appear in an interesting 

 light if we compare this insect with Cremastochilus. The larval and 

 pupal Microdon are synceketes and are usually indifferently tolerated. 

 Occasionally, however, the ants attack them even in these stages 

 although they are well protected by their hard skins and marginal 



