4 OHIO STATE ACADEMY OF SCIENCE. 
I desire Ao study: materialyfrom-all parts of .North America 
and offér.to name’spécimens foe! anyone who will send them in; 
asking nothing for the naming except such CSU as the 
sender . himself is pleased. to. donate. “) 
It is the desire to make. this paper ARE enough to be Bh 
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 sa places. 
All of the Chrysops whose eg ¢ laying habits [ 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 Nymphez 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 
