18 



strongly chitinized hooks, and work by being moved endwise,, 

 backward and forward. When drawn in the anterior ends point 

 directly forward, but when protruded these same ends point 

 downAvard and backward, thus forming a pair of hooks by 

 means of which the larvte hold their prey, consisting of a va- 

 r'ety of invertebrates of various sizes. They are able to pro- 

 trude these mandibles very quickly, and when they strike a 

 hard object a grating sound is produced. A careful study of 

 the food of the larvae of horseflies is of more than ordinary 

 interest, since it is claimed by some that, as they are predaceous, 

 tlicy may take enough injurious species to admit them to the 

 roll of beneficial insects. 



The color of the full-grown larva is dull whitish in general, 

 but there is a conspicuous band of black or dark brown at the 

 inion of each two segments. For part of the length the bands of 

 Hack are but slightly narrower than the others. 



In the species under consideration the pupa stage was 

 reached by the middle of May, or before, and lasted about two 

 weeks. It is likely that the change to the pupa occurs much 

 earlier in Louisiana than in Ohio. It may be best to state here 

 that this horsefly is a species which occurs almost continuously 

 during the sunnner season, so that the date of pupation probably 

 varies with the specimens without regard to seasons. The pupa^ 

 of this fly is about an inch and a quarter in length. 



ON CERTAIN CONDITIONS PRESENT IN LOUISIANA. 



Horseflies appear to be very abundant in Louisiana, espe- 

 cially in certain sections, and in the light of what "has been said 

 already there seem to be valid reasons for this condition. An 

 atlas which I use for reference contains this statement in 

 regard to the general relief of the State : 



"Remarkably low and level, with slight elevations in the 

 west. About 8,450 squar-e miles are subject to overflow, making 

 h^vees necessary." 



The total area of the State is given as -19,626 square miles, 

 s.i we have figures to show fhat one-sixth of the entire State 

 is subject to overflow if levees are not constructed. There are 

 many rivers and small streams in nearly all sections, together 

 with many fresh water lakes, and with the swamps and marshes 



