152 Journal New York Entomological Society. [Vol. xxv. 



and fresh egg-masses are easily recognized by their color, but in the 

 course of a few hours the color changes first to gray then to shining 

 black, and the majority of the egg-masses found are of this color. 



The egg-masses or egg-clusters in Chrysops callidus are elongate 

 in shape and much flattened, tapering at both ends, especially so at 

 the upper end; the lower half may be abruptly truncate. Each clus- 

 ter consists of a single layer of eggs (as Harf has previously stated), 

 which are regularly arranged in oblique rows : their whole arrange- 

 ment being like that of shingles on a roof, with the difference that 

 the lower eggs overlap the upper ones to about three quarters of 

 their length; hence the arrangement is precisely the opposite of 

 what one should expect if the intention were to prevent rain water 

 from penetrating between the eggs. However, the whole mass, 

 especially when a few days old, presents an almost perfectly even 

 surface, and full protection against moisture is afforded by a thin 

 shining outer layer or membrane, which seems to be a secretion of 

 the eggs themselves covering the whole mass soon after oviposition 

 is completed. It is only after piercing this membrane that individual 

 eggs can be removed from the cluster. (See plate X, fig. 2, which, 

 however, represents an egg-cluster of a somewhat irregular shape.) 



The egg-cluster may contain from 250-300 eggs (actual counts 

 gave 277 in one case, 260 in another). The single egg (Plate X, fig. 

 3), is spindle-shaped, tapering at both ends, but more so at the hind 

 end, by which it is attached to the surface. After oviposition, it is 

 at first s"emitransparent, and contains, in its upper third, an opaque 

 whitish mass, apparently yolk. This yolk chiefly determines the 

 whitish appearance of the cluster. 



The arrangement of the eggs in the cluster is, of course, the 

 result of the special manner in which the eggs are deposited by the 

 female. 



In the act of laying, the adult fly sits, as" stated, always head down- 

 wards on the stem or leaf of the plant selected, and begins, after 

 repeatedly trying out various places, by placing one egg about in the 

 middle of the leaf (Typha) ; it then places a second egg on the side 

 of this, but a little farther down. Evidently the fly first touches the 

 first laid egg with the tip of the abdomen, and then moves the ab- 

 domen slightly downwards, by a movement which depends on or is 

 determined by the resistance found in touching the first-laid egg. 



