i6 OHIO BIOLOGICAL vSURVEY 



fouud in amber: Voliccella, Crior/mia, Eristalis, Helophiliis, Merodon, 

 and Mile si a. 



GENERAL CHARACTERS: THE EGG 



The eggs of this family that I have seen (mostly of aphidophagous 

 species) are all chalk-white in color, and hence conspicuous on the darker 

 surface of the leaf or twig on which they are usually deposited. They 

 are elongated-oval in outline, subcylindrical, truncated at the micropjdar 

 end, rounded at the opposite end; flattened slightly to the surface on 

 which they are deposited, slightly humped above. The length is fre- 

 quently a little less than one millimeter. 



The entire exposed surface of the shell, except a small region around 

 the dark micropyle, shows a delicate and very beautiful sculpturing, con- 

 sisting, in aphidophagous species, of numerous microscopic elevations of 

 the surface, arranged in lines obliquely around the egg. Each of these 

 elevations has a main body, longer than wide, and radiating from this a 

 greater or lesser number of delicate, arm-like projections extending into 

 the spaces between adjoining bodies. The arms may branch slightly and 

 may end freely, or meet similar processes from the same or other bodies; 

 often making a rather complex network of slender white arms between 

 the larger elevations. (Figs. 17, 43, 63, 143.) 



CHARACTERS AVAILABLE FOR CLASSIFICATION 



I know of no naked-eye characters that are specific. However with 

 further study we may be able to distinguish the eggs of many species 

 microscopically. There is a considerable variation in size of the eggs, 

 especially between the different genera. In addition to this the charac- 

 ters which are likely to prove useful are to some extent the shape of the 

 egg; the .size, shape, and number of the elevated, sculptured bodies on the 

 shell; the number of arms radiating from them; the relative width of sepa- 

 ration of the bodies; etc. These characters are difficult to see clearly, 

 requiring high magnification and very favorable illumination. 



The time of oviposition for the aphidophagous species may be said 

 to be considerably correlated with that of the appearance of aphid 

 colonies. The others are subject to the usual .seasonal conditions. No 

 definite dates can be given which are generally true except to say that 

 ovipo-sition for the first spring generation commonly takes place very soon 

 after what we recognise as the Spring awakening of our fauna and flora. 



The duration in the egg-stage was determined for two species (see 

 under Syrplius amerieanus p. 55 and Allograpta obliqua p, 58 ) in which 

 it ranged from 55 hours to 3.5 days (indoors.) The egg-stage of 

 Mcsogramma poliia is said by Ashmead to be three or four days. 



