SYRPHIDAE OF MAINE. 



the puparium which was found floating on the water of a lake> 

 The larval habit was not determined. 



On July 7, 1915, at Orono a larva of this species was col- 

 lected in partially decomposed human excrement near the mouth 

 of a sewer. It was apparently full grown by July 19, pupated 

 between the 2ist and 27th and emerged from the puparium 

 August 6. 



On July 10 a gravid female was captured at the same spot 

 and enclosed with a male over a small mass of the moist excre- 

 ment. By one o'clock of the same day a mass of several 

 hundred eggs had been deposited by this female. By July 14, 

 7 A. M., nearly all of the eggs had hatched and the young 

 larvae were submerged except for the posterior respiratory 

 appendage in the moisture at the bottom of the jar. The larvae 

 were kept in cages and were about full grown on September 9. 

 Three hundred and eighty-seven eggs were dissected from the 

 ovaries of a female taken about human excrement on July 21. 

 On July 27 seven puparia were taken from the drier parts of 

 the mass of excrement. One of them which had apparently 

 just pupated emerged August 8 ; others from July 28 to August 

 i. 



Egg. (Fig. 36-1, 2 5). Sub-cylindrical, elongate-ovate in outline, a 

 little smaller and more truncate at the micropylar end, slightly curved 

 on its long axis. The length of specimens measured varied from .82 

 to .86 mm., with an average of .84 mm; the maximum diameter was 

 very uniformly .255 mm. Color white, glistening. The markings or 

 sculpturing of the chorion (Fig. 36-^) are characteristic, although ap- 

 proached closely by Syritta pipiens (See p. 253). It consists of small, 

 irregular, polygonal areas, which are slightly raised, leaving between 

 them narrow, parallel-sided and rather smooth-sided channels; the 

 latter connecting with each other to make a fine dark network over 

 the surface of the egg. Each of the areas thus marked off is further 

 ornamented on its surface with about 20 to 40 circular areoles by the 

 slight depression of the surface between them. When viewed under 

 very high power (oil-immersion objective and 3-4 inch ocular) the 

 minute circular areoles are seen to be formed by the arrangement of 

 very fine finger-like elvations, (Fig. 36-1). 



The polygonal areas are of such a size that about thirty occur end to 

 end the length of the egg and about fifty or sixty side by side around it. 



Egg-laying was observed from July 10 to July 21 ; but, since 

 a good-sized larva was found as early as July 7 and since 

 adults continued to emerge at least until August, the egg-laying 



