No. 568] BIOLOGY OF THE THYSANOPTERA 



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Additional Data Bearing on the Life Cycle and Sex 



In view of the fact, to be discussed later, that Anapho- 

 thrips striatus has hitherto been known almost exclu- 

 sively in the female sex, and is known to reproduce par- 

 thenogenetically, and the fact that in the collections here 

 recorded the males constitute nearly 25 per cent, of the 

 total, the question arises, are these males functional? If 

 not functional in this species, are the males functional in 

 other species? A number of observations and experi- 

 ments I have made bear on these questions. 



A single pair of Anaphothrips striatus was found copu- 

 lating in nature, which Uzel would have considered proof 

 that parthenogenesis did not occur. The testes of the 

 males are plainly visible without dissection. Suspecting 

 that they might not be fleshy organs at all, but chitinized 

 structures, perhaps vestiges of testes, I boiled a number 

 of specimens in caustic potash. The testes disappeared, 

 from which I judge they are not merely chitinous bodies. 

 I can say nothing of their cellular nature, owing to the 

 loss of material killed and fixed for that purpose. Nu- 

 merous sections of another species Anthothrips verbasci, 

 however, reveal well-developed testes. Cell divisions 

 (probably the spermatocyte divisions) and nearly mature 

 spermatozoa in bundles were observed in these sections. 

 Though the number of chromosomes could not be deter- 

 mined, it is an interesting fact that spindles in side view 

 usually showed a lagging chromosome. 



Finally, with further regard to the functioning of 

 males, I have attempted to breed several species par- 

 thenogenetically. The results in the case of Euthrips 

 tritici were so far encouraging that two larva? appeared 

 on the plant on which virgin females had been previously 

 placed. But in these cases I could not be certain that the 

 food plant was uninfected. Experiments with Anapho- 

 thrips striatus and Anthothrips verbasci gave negative 

 results, but in each case failure to obtain young by par- 

 thenogenesis may have been dne to the conditions. 



Some observations on the place of pupation may also 



