520 



HEMIPTERA. 



SO on almost indefinitely, experiments having shown that the 

 power of reproduction under such circumstances may be exer- 

 cised, according to Bonnet, at least through nine generations, 

 while Duval obtained thus eleven generations in seven months, 

 his generations being curtailed at this stage not by a failure 

 of the reproductive power but by the approach of winter, 

 which killed his specimens ; and Kyber even observed that a 

 colony of Apliis dianthi, which had been brought into a con- 

 stantly heated room, continued to propagate for four j^ears in 

 this manner, without the intervention of males, and even in this 

 instance it remains to be proved how much longer these phe- 

 nomena might have 

 been continued." Dr. 

 Burnett, from whom 

 we quote, considers 

 this anomalous mode 

 of increase of indi- 

 viduals as a process 

 of bxdcUng, and that 

 the whole series, like 

 the leaves 'of a tree, 

 constitutes but a sin- 

 gle generation, which 

 results from the union 

 of the sexes in the 

 previous fall. It has 

 Fig. 517. always been sup- 



posed that the final autumnal set of individuals were males 

 and females alone. But Dr. Burnett states: "-The terminal 

 l)rood has hitherto been considered, as far as I am aware, to be 

 composed exclusively of males and females, or, in other words, 

 of perfect insects of both sexes. I was surprised, therefore, on 

 examining the internal organs of the non-winged* individuals, 

 to find that many of these last were not females proper, but 

 simply the ordinary genimiparous form. Moreover so great 

 was the similarity of appearance between these two forms — 

 true females and gemmiparous individuals — that they could 

 be distinguished only by an examination of their internal 

 Sfcnitalia." 



