Vol. XXX] ENTOMOLOGICAL NKWS. 135 



they are forced to aggregate at the horders. On the other hand, 

 being dependent on moisture, they do not usually go any great 

 distance away from these borders. 



It is not difficult for the entomologist to identify the Tabanid 

 larvae as such. The larvae are nearly always cylindrical in 

 shape, whitish, grayish or yellow in color, and characteristical- 

 ly hard and firm to the touch. This is due to their strong 

 chitinization and their contraction at the moment when they 

 are taken. They generally will soon begin creeping and then 

 will appear more slender and more pointed at the cephalic end. 

 The small larvae of Chrysops are usually taken when between 

 5 and TO millimeters long; the smaller ones escape attention. 

 The Chrysops larvae are whitish or greenish yellow, the end of 

 the abdomen often darker. The Tabanns larvae are found in 

 all sizes from 5 to 45 millimeters, more frequently, however, 

 of the medium size. They are usually whitish, yellowish or 

 reddish grey, either without pattern and shiny, or with gray 

 or brown transverse markings. In all larvae the proleg-bearing 

 ridges may be quite conspicuous. The larvae of most species 

 do not float at the surface but sink to the bottom of the 

 water ; certain species as, for instance, T. I'm col a and T. atni- 

 tus, have inflated tracheae and float at the surface when washed 

 out of their habitat. This facilitates their capture, and in 

 places where these larvae alone occur, a strainer is not neces- 

 sary. All that is needed is to throw lumps of mud and sod, 

 grass, bushes, etc., from the edge into the water, stir them -and 

 work them over for a while and the larvae will soon rise to 

 the surface where they betray their presence through vigorous 

 wriggling or lashing movements. 



Together with the Tabanid larvae, one may obtain, by means 

 of the strainer, the larvae of other Dipterous families, chiefly 

 Dolichopodidae, Leptidae and Tipulidae. The former two 

 families comprise larvae usually of the size of Clir\sops larvae 

 but more slender, shiny white or yellowish, the end of the 

 body not pointed or rounded but truncated or ending in several 

 lobes. The Tipulid larvae, when belonging to larger species, 

 are generally gray or blackish in color; those belonging to 



