34 OHIO BIOLOGICAIv SURVEY 



of the eyes, their pilosity and the size of the facets are somewhat 

 unstable, but often useful characters. 



From the thorax we occasionall}^ get characters in the shape or 

 ornamentation of the scutellum. In the legs, length, thickness of special 

 parts, vestiture, peculiar spines, etc., are of value, though often confined 

 to males only. In the abdomen, shape, flattening, length, width and 

 de])ression, and occasionally peculiarities of certain segments and of the 

 hypopygium, are to be considered. Williston makes the interesting 

 observation that the species with slender abdomen are quickest on the 

 wing, the short, thick-set ones never soaring but commonl}- resting on 

 flowers and leaves. 



Color-markings are very extensively used in this family- both as 

 specific and as generic characters. In some genera they are very reli- 

 able, in others practically worthless. In general it is best not to rely 

 upon them unless coupled with definite structural characters. 



Macrochaetae are conspicuously rare in this family, and hence the 

 vestiture is of decidedh' secondar}- importance. A few genera have 

 bristles; elsewhere the only characters are relative density- or .scarcity of 

 pile or pube.scence; or the pollenosit}' of special parts. 



The adult insects of many .species have .several periods of common 

 occurrence each .sea.son. Little can be said in a general way about the.se 

 dates. We have been much surprised to find how early in vSpring, adult 

 Syrphids maybe taken. In 1910 and 191 1 a number of species were 

 taken the last few days in March and the first of April about blo.ssoming 

 Willow {Salix sp). Some species are probably active as soon as the first 

 flowers bloom in .spring, and .some are to be found all summer long, and 

 as late as November in autumn. 



I am not aware that there are any accurate observations as to the 

 length of life of the adults. I found the Syrphidac did not thrive in cap- 

 tivity, and though they could be kept alive for a short time on sweetened 

 water, the}- were very readily killed b}' adverse conditions. Buckton, 

 however, relates an instance in which a decapitated Eristalis tcnax lived 

 for three days and nights on a microscope-.stage. Certain observations 

 lead me to believe that the adults do not ordinarily pa.ss the winter. 



In consideration of the very remarkable divergence of larval habits it 

 is suprising to find that the adults almost all have the same, or very similar, 

 habits of life. Larvae which are predaceous, phytophagous, aquatic, or 

 live in the foulest of excrement, all transform to adults which are char- 

 acteristically attracted by two things, viz., flowers and sunshine. Not 

 many kinds of images will be taken away from flowers and not man}- are 



