STREPSIPTERA. 



737 



Order 20. STREPSIPTERA.* 



Minute insects ; males freely flying with large metathoracic 

 wings, the mesothoracic pair being reduced to small dimensions 

 (p. 61o) ; no cross nervures. The parasitic female is reduced to a 

 blind, almost formless sac. 



These extraordinary insects are by some authorities classed 

 with the Coleoptera. Their life history is as follows. The egg 

 whilst still within the body of the mother, which it must be re- 

 membered is a parasite shut up inside the body of some Hymenop- 

 terous or Hemipterous host, gives rise to a small active, six-legged 

 larva, known as a triungulin, so called from the three processes 

 at the end of each tarsus. 



A single mother may give 

 rise to many hundreds of 

 these microscopic, active 

 larvae, which find their 

 way on to the outside of 

 the body of the host. 

 Sooner or later they reach 

 the larvae of the host, 

 and boring their way 

 through the skin enter 

 these larvae and com- 

 mence to feed on their fat 

 body. When the host's 

 larva pupates, the larval 

 parasite pushes one end of its body through the soft membrane 

 uniting two of the abdominal segments. If this host-larva is 

 about to turn into a male, the parasite in turn pupates, and 

 from the pupa emerges the winged and active male Strepsipteron ; 

 but if the host -larva be destined to become a female, the parasite 

 undergoes little but retrogressive change, until it becomes a 

 female Strepsipteron so degenerate that it is still a matter of 

 dispute as to which end represents the head and which the tail. 

 The male seems to live but a very short time ; in the case of Xenos 

 about twenty minutes, whilst the male Stylops lives a day or two, 



* Von Siehold, Arch. Naturg., ix, 1843, p. 137. Newport, Tr. Linn. 

 Soc. xx. 1851, p. 351. Nassonoff, Zool. Centrbl, i, 1894. Meinert, Ent. 

 Meddel, v, 1896, p. 148, and Ov. Danske. Selsk., 1896, p. 67. Brandt, 

 Hor. Soc. Ent. Boss., xiv, 1879. 



Z III 3 B 



FlG. 470. Stylops childreni (after Kirby). a larva 

 b female : c male. 



