Syrphidae of Maine. 157 



From one of these puparia left out-of-doors, a female 

 emerged June 18, another June 22, while a third disclosed 26 par- 

 asites (undetermined) July 8th, the entire lot emerging from 

 a single small hole gnawed thru the anterior end of the pu- 

 parium (Fig. 9, B). The exact date of pupation, i.e., whether the 

 full-grown larvae passed the winter, pupating in spring, or 

 whether pupation occurred sometime in a'utumn has not been 

 determined, — probably the latter. Several full-grown larvae 

 were collected by Mr.Fletcher among Myzus cerasi (Fab.) on 

 cherry, July 18, 1917. 



It appears likely that there are two more or less complete 

 generations of this species, annually, though not occurring in 

 very definite broods. Adults from overwintering larvae or pu- 

 pae evidently giving rise to the larvae which have been found 

 full sized by early July ; and the adults from these larvae pro- 

 ducing another generation, the larvae of which occur especially 

 during August. A partial third generation from eggs deposited 

 by females visiting the colonies of aphids the last week in Au- 

 gust, seems probable. 



Egg (Fig. 8, A). Lengths of seven eggs measured were 0.861, 0.8815, 

 0.89175, 0.9225, 0.9532, 0.975, and 0.9942 mm., respectively, the average 

 0.925 mm. ; their greatest diameters were respectively 0.3075, 0.308, 0.315, 

 0.328, 0.3375, 0.3485, and 0.3485 mm., the average 0.3275 mm. 



The egg is of about the usual sub-cylindrical shape, somewhat in- 

 flated in the middle and with the micropylar end a little smaller and more 

 truncate than the opposite end; also with the ventral surface flattened 

 somewhat to the twig on which it is deposited. Color white, glistening. 



The characteristic thing is the sculpturing of the chorion the micro- 

 scopic pattern of which (Fig. 8, B) suggests at first glance a very large 

 number of minute, 8-rayed spider webs, or hexagonal wheels, contiguous 

 to each other, with a very small elevated body in the center of each. Tak- 

 ing each "web" as a unit it may be described as consisting of a very small, 

 sub-conical, elevated body in the center of the web (the hub) from which 

 radiate eight, slender, slightly elevated arms arranged in four pairs. The 

 two arms extending from the central elevation, or hub, toward either pole 

 of the egg, radiate like the spokes of a wheel ; while the two which extend 

 in the transverse direction from either side of the hub (i. e. perpendicu- 

 lar to the long axis of the egg in a plane parallel to it) run practically 

 parallel to each other. A series of these parallel arms, together with the 

 hubs they connect make a ladder-like chain running almost transversely 

 (sometimes somewhat obliquely) around the egg. The individual units 

 are closely contiguous to each other so that each arm forms a spoke for 

 two central bodies or hubs, and the rim of the imaged wheel is formed 

 only by adapting the contiguous spokes of adjoining wheels. The pattern 



