IO ENTOMOLOGICAL NEWS. [Jan., '07 



Litomastix truncatellus oviposits in the egg of various spe- 

 cies of Plusia. The eggs of the parasite, which may be fer- 

 tilized or parthenogenetic, are deposited singly, but occasionally 

 the same female returns and deposits a second egg within 

 that of the host. Several females may select the same egg, 

 but this probably occurs rarely under natural conditions. The 

 course of development of the fertilized and the parthenogenetic 

 eggs is the same but, as in the bees, the fertile egg gives rise 

 to females, while the unfertilized egg produces only males. 



Silvestri found in the maturation and early segmentation 

 stages of the egg, features of great interest from an embryo- 

 logical viewpoint, but too technical for discussion here. It 

 may be mentioned in passing, that the polar nuclei and their 

 protoplasm do not degenerate but, later, form an envelope 

 which surrounds the germinal region. 



In the development of the egg there occurs a process of poly- 

 embryony which, however, differs in detail from that re- 

 ported by Marchal for Encyrtus and Polygnotus. One of the 

 most striking features is that there are developed two very 

 different types of larvae. From a single egg there originate 

 about a thousand normal larvae of the form typical of endo- 

 parasitic hymenopterous larvae. In addition to these, there are 

 produced one hundred or more vermiform asexual larvae. 

 These lack any trace of circulatory, respiratory or genital sys- 

 tems, or of malpighian tubes. They are provided with strong- 

 ly-developed mouth parts. 



The sexual larvae transform into pupae when the host larva 

 has completed its growth, and later, into adults. The asexual 

 larvae, on the other hand, degenerate completely, never giving 

 rise to adults. 



At first thought it might seem that these asexual larvae are 

 abortive forms, without special function. Considering, how- 

 ever, the development of their mandibles, and of the skeletal, 

 muscular, and digestive systems, it appears to Silvestri natural 

 to believe that, being able to penetrate readily the organs of 

 the body of the host-larva and having mandibles especially 

 adapted for tearing, they have the function of breaking down 



