204 Journal New York Entomological Society. [Vol. xvi. 



and are then found near or at the entrances. They creep very slowly, 

 with a wave-like motion of the flat and viscid ventral surface, which 

 so closely resembles the foot of a slug, and keep the fringed border of 

 the body in close contact with the surface over which they are moving. 

 The anterior end, however, is occasionally raised for a few moments. 

 At such times one may see the small pointed head of the larva moving 

 about uneasily under the fringed border as if in search of food. What 

 this food is, has not been determined, Laboulbene (1882) surmised 

 that it might be the ant larvae, but I am inclined to believe that it is 

 the minute pellets of food, which, after their moisture has been ex- 

 tracted, are ejected from the hypopharyngeal pockets of the worker 

 ants. These pellets are scattered about the nest, especially about the 

 superficial galleries, and though hard and dry, must contain consider- 

 able nutriment. They are probably eaten not only by the Microdon 

 larvae but also by many other synoeketes (Clytra, Coscinoptera, etc.). 



The larvae of the common European and North American Micro- 

 dons are usually of a dirty white or drab color, with yellow or brown 

 fringes of hairdike processes around their creeping sole, and a promi- 

 nent, heavily chitinized tubercle near the posterior end. Usually no 

 traces of segmentation are to be observed in their elliptical bodies, 

 but in some adult larvae of M. tristis, just before pupation and after 

 their upper surfaces had been dried by exposure to the air, 1 have been 

 able to discern in certain lights a distinct division of the body into 

 seven or eight subequal segments. When the time for pupation 

 arrives the larva remains stationary on its creeping sole, contracts 

 somewhat, becomes harder and more convex and of a deeper brown 

 color. The reticulations or markings, with which the upper surface 

 is sometimes ornamented, become more pronounced, and a pair of 

 short tubercles or protuberances make their appearance near the an- 

 terior end in addition to the single respiratory tubercle at the pos- 

 terior end. 



I am convinced that there is but one annual brood of these insects, 

 at least in temperate regions, and that the larvae, after passing the 

 winter in the ant-nest, pupate in April or May. The flies hatch 

 early in June and are much less active than other Syrphidae. They 

 are most frequently taken in sweepings in meadows or rather low 

 grounds. During July young larvae may be found in the nest and 

 these mature by autumn. I believe, therefore, that Mann (1882) 

 must be mistaken when he claims to have seen several specimens of 



