1914 ENTOMOLOGICAL SOCIETY. 57 



Contraction of the anal cell losers. 

 Anal cell conservers. 



Second anal vein conservei's .Lycaotince 



Tenthredinince. 

 Cimbicirvce 



Second anal vein losers. 



Second anal cell reduced by atrophy. 

 Costal area conservers. 



Eadial cross-vein conservers HoplooampincB 



Dineurince 



Eadial cross-vein losers MonoctenincB 



Cladiince 

 NematinoB 



Costal area losers lUennocampinoe 



FenusincB 

 ScoUoneurince 



Second anal cell reduced by coalescence fli/lotonmice 



Schizocerince 



Anal cell losers Acordulecerince 



There are many facts in the development of the Tenthredinoidea of great 

 interest. One of these is the method of reproduction of many of the species. A 

 great variation exists in the number of individuals of the two sexes; in only a 

 few species are the males as numerous as the females. The males, while fre- 

 quently differently colored, do not ordinarily differ markedly in structural charac- 

 ters, though they are usually smaller in size. The number of males is always 

 less, not only among captured, but among bred individuals. Males are unknown 

 in certain species, while in others, where the males are known, the females repro- 

 duce parthenogenetically. Practically none of the American species have been 

 experimented with from this point of view, but much has been written with regard 

 to the European forms. Von Siebold has shown that males are unknown for 

 about one-fifth of the German species and Cameron that they are unknown for 

 about one-third of the British species. The fact that no males are known for 

 any given species does not signify that the species reproduces only partheno- 

 genetically, for many of the species are rare, in many cases only a few individuals 

 have been collected, the number of males is always much less than that of the 

 females, so that the possibility of the collection of males is much less. It has, 

 however, been shown conclusively by many different investigators that eggs laid 

 by virgin females of certain species will produce larvse. The parthenogenesis is 

 a mixed one, for among the known parthenogenetic species males are known for 

 certain species and in the case of these species larvae may be produced from eggs 

 laid either by virgin females or impregnated females. The conditions would 

 suggest that the parthenogenesis was a progressive one, for in certain species the 

 eggs laid by virgin females produce both males and females, in others only males, 

 and in still others only females. The known parthenogenetic species all belong to 

 the family Tenthredinida?. Pteronus rihesii and Lygaeonemafus erichsonii are 

 well known examples. 



