78 Mr. P. Cameron on the 



would yield males or females. The unfertilised eggs of 

 S. cingulatus might produce males ; but the probability is 

 that Hemicliroa riifa and Pliyllotoma nemorata would 

 give issue to females, seeing that no one has ever caught 

 or bred the males of these common species. There is 

 equally good evidence that complete parthenogenesis occur 

 with Eriocampa ovata, L., and PoecUosoma pidveratum. 

 Fall, (obesimi Klug.). The late Frederick Smith once bred 

 between 300 or 400 flies from the larva; of E. ovata, and 

 not one of them was a male, while it has recently been 

 shown by Mr. Bridgman* that an unfertilised female can 

 lay fertile eggs, but Mr. Bridgman's larvas unfortunately 

 died young. I have] shown too elsewhere i" that P. pul- 

 veratum (whose- male is unknoAvn) is a parthenogenetic 

 species. I think then we are justified in concluding that 

 complete and mixed parthenogenesis exist in the Tentlire- 

 dinidce. 



Von Siebold in his book has analysed Ilartig's Blatt- 

 ivespen in reference to the scarcity of males with these 

 insects, and shows that Hartig was apparently unac- 

 quainted with the males of 7G species out of a total of 381. 

 Since the publication of Hartig' s classical work, our know- 

 ledge of the habits of saw-flies has enormously increased, 

 while the differences between the sexes are much better 

 understood. Still, with all that, the males of many species 

 remain to be discovered. I find that out of some 330 

 British species, the males of 53 have yet to be found. No 

 doubt many of these are rare and little known forms, so 

 that much stress cannot be laid on them as showing the 

 scarcity of males, but the same result is shown in another 

 way. Tabulating the British species in my collection, I 

 find that, in addition to the maleless species noted above, 

 54 species are represented by females only, so that 

 altogether I have never seen the males of 107 species. 

 In the large genus Nematus, the males are very much 

 rarer than the other sex, even with common species. 

 Nematus pavidus, | for example, is a species I breed regu- 



* Ent., 1878,191. 



t Ent. M. Mag., xv., 12. 



J Last autumn I found about tvro dozen of the larrse of this species on 

 a willow bush, nearly full-fed. They were placed in a jar together with 

 not more than a, day's supply of food, and forgotten for a week. Most of 

 them were then found dead : two spun cocoons and yielded ichneumons 

 (Mesoleius opticvs), and three had turned to pupa? without spinning a 

 cocoon. These proved to bo two males and one female, the former of the 

 usual size, the latter rather small and dark coloured. 



