160 THE EARLY STAGES OF TABANID^ 



"The terminal abdominal segment [Plate 12, Fig. 143, a, b] shows a sexual 

 distinction in the arrangement of the short spines midway on the ventral side, 

 anterior to the terminal teeth. In the male ten to twelve of these spines form 

 a continuous serrated border. In the female the spines occur in two groups of 

 four to six spines similar to those of the male, but separated by space equal in 

 width to that of one of the groups." 



"The terminal teeth of the posterior segment are arranged with two pairs 

 close together on the dorsal side and one pair on the ventral side. These teeth 

 are black-tipped and acute; all of them are directed slightly outward. The 

 lateral teeth of the two dorsal pairs are the longest. The ventral pair is smaller 

 and is set slightly in from the periphery of the segment." 



"After the final ecdysis which results in the formation of the puparium, the 

 nymph, at first a light green, gradually changes to yellow. Upon the second day, 

 the eye spots change from yellowish to pale brown, then to a chocolate color. 

 Beginning with the third day the pads of the wings and the legs, at first light 

 brown, assume the same color as the eyes. The chitinous pad enveloping the 

 wing is densely opaque, so that only the plications of the developing wing can 

 be discerned. Upon the penultimate day, the fifth or sixth usually, the abdomen, 

 which heretofore has been a uniform yellow-brown, becomes striped with light 

 orange and brown, which colors gradually deepen until the time of emergence." 



The process of emergence from the puparium is also described by 

 Mitzmain (Plate 12, Fig. 152, b): 



"In emergence, the puparium which lies buried to some depth in the sand is 

 invariably dragged to the surface where the final acts of emergence are com- 

 pleted. Two or three days prior to the act of emergence, the puparium shows 

 considerable mobility when disturbed by handling or stimulated by light. Cer- 

 tain movements, which one learns through numerous observations to be charac- 

 teristic, can be considered as actually premonitory. These occur usually from 

 ten to twenty minutes prior to the breaking of the cuticle, and serve the observer 

 as warning signs. If during this interval a low power lens is focussed on the 

 compound eye, the epidermis of the fly separating from its connective tissue fas- 

 tening of the puparium can easily be seen. This action resembles strikingly a 

 wave of water moving between the walls of the puparium and the epidermis of 

 the fly. It may be considered as the movements of a semiliquid layer between the 

 fly and its puparium. Another movement, which can be observed within a few 

 minutes after that previously described, is the momentary contraction and ex- 

 pansion of the sides of the abdomen between the two lateral ridges. This too, no 

 doubt, is effective in tearing the connective tissue lining to facihtate emergence. 

 A few minutes later the anal end of the abdomen is torn loose from its fastening, 

 and emergence of the fly begins." 



