4 OHIO STATE ACADEMY OF SCIENCE. 



I desire to study paterial, from all parts.of.^North America 

 and' offer to name specimens for anyone who will send them in; 

 asking nothing for the naming except such specimens as the 

 sender himself is pleasfed to donate. 



It is the desife to make this paper plain enotigh to be easily 

 understood, but the student must understand that it is necessary 

 to have perfect specimens in order to be sure of his results in all 

 cases. Many of the characters used in determining species in this 

 family are easily damaged, consequently in collecting and pinning 

 great care should be exercised. 



EGGS AND EGG-LAYING. 



All the species of the family I have observed ovipositing, 

 place their eggs on some object that projects from and overhangs 

 the water or that stands in wet and marshy places. 



All of the Chrysops whose egg laying habits I know and 

 many species of Tabanus place their eggs over water while other 

 species of Tabanus oviposit on plants standing in wet ground. 

 Some species are very precise in placing their eggs. Thus T. 

 stygius, which is a very common species at Sandusky, follows 

 the interesting habit of ovipositing on the upper surface of the 

 leaves of Sagittaria just above the point where the petiole meets 

 the expanded part of the leaf. 



So closely is this habit followed that a hundred masses of 

 eggs are found thus located to one placed otherwise. _ A few 

 masses were observed on Nymphae leaves but located exactly as 

 when placed on Sagittaria. Only a very few masses were ob- 

 served not placed in exactly the same position in reference to the 

 leaves on which they were found. 



In a certain marshy place where I have seen, in different 

 years, numerous masses of eggs of T. atratus I noticed that these 

 masses were nearly always found on the same species of Scirpus 

 and situated very much alike in the great majority of cases. 



I have watched several females of C. callidus during the 

 entire process of oviposition which in this species usually occupies 

 from twenty minutes to half an hour ; during which time some- 

 thing like one to three hundred eggs are laid. 



The female alights on the leaf head downward and begins 

 by pushing the tip of her abdomen forward toward the sternum 

 of the thorax and placing the protruding end of an egg against 

 the leaf. This end sticks fast and she then moves the tip of her 

 abdomen backward until its normal position is reached and the 

 egg becomes free. By the same movement one or two eggs are 

 then placed to one side of this one and two or three on the other 

 side of it. The unfinished end is soon observed to be V-shaped; 

 the female moving very gradually forward and placing the end 



