326 



Habits of the GrcenlKnise White Fly 



attached independently to the distal end of the second tarsal seg- 

 ment. 



Wings (Figs. 52, 53). There are two pairs of wings in both male 

 and female, and the venation of both fore and hind wings is exceed- 

 ingly simple. There is a series of knob-like structures running round 

 the wing margin, each knob supporting two or three hairs (Fig. 54). 



Poittvt-fi 



Poittvttiv 



Fig. 52. Fore wing. 



Fig. 53. Hind wing. 



Fig. 54. Wing margin. 



Tracheal system. The tracheal system is very complicated, as in the 

 pupa, and there are four pairs of spiracles situated as follows: a pair 

 each in the pro- and meta-thorax; a pair on the first abdominal seg- 

 ment placed a Httle antero-dorsal to the anterior pair of wax plates; 

 a pair on the sides of the vasiform orifice, ventro-laterally. 



/V^^Vly^ox". 



Fig. 55. Vasiform orifice. 



[Quaintance^ in his Classification of the Aleyrodidae, states that 

 there are three pairs of thoracic spiracles in the Aleyrodidae. Wood- 

 worth*, in A. citri, had also described three pairs.] 



Vasiform orifice (Fig. 55). The function of this peculiar apparatus 



