The Scottish Naturalist. 157 



male. In ^gilips and Megapdmus both sexes are equally 

 common. 



Parthenogenesis has been clearly demonstrated in Neniatus 

 ribesii {ventricosiis) the common gooseberry sawfly, by the re- 

 searches of Thorn, Kessler and more especially by Von Siebold, 

 (see his '' Beitrage zur Parthenogenesis der Arthropoden " pp. 

 107-130). In this species the result of the parthenogenetic 

 brood is male, as is the case with Apis, Polistis and Vespa. 

 Parthenogenesis also appears to occur with Xematus 7?iiliaris, 

 Pz. {viridis H.), a very common saw-fly, with 2 or 3 broods in 

 a year, and which has the males nearly as numerous as the 

 females. I had 4 larvae of 7?iiliaris in a bottle by themselves. 

 They spun up, and at the end of July 4 females came forth. I 

 supplied them with a fresh willow leaf, and one of the creatures 

 laid 4 or 5 eggs on it, from which in due time larvae issued, but 

 unfortunately they did not reach maturity, having perished 

 during the winter in the cocoons. 



The number of saw-flies of which no males are known is not 

 inconsiderable. There are some widely known species which 

 have been frequently bred, and hundreds caught, yet no males 

 have been discovered. This is the case with Dineura ver?ia, 

 HcmicJiroa rufa, Phyllotoma nemorata, Bk?inocampa luteiventris, 

 B. albwes, Poeciloso?na pidveratum, P. luteola, Hoploccwipa 

 brevis, Eriocainpa ovata, Fenusa betulce. With others again the 

 males are known, but are extremely rare. Stro?igylogaster 

 ciiigidatus I have taken in hundreds, and have only managed 

 to secure one male, which I bred. N'e?natus gallicola has been 

 extensively bred by Mr. F. Smith, and he only " obtained a 

 single male out of several hundreds of the flies " (Proc. Ent. Soc. 

 Lond. part iii. 1876. p. 22). Croesus varus is only known to 

 have a male from the rather doubtful account of its original 

 describer, Villaret ; and that of Blennocainpa epjnphium from a 

 single specimen taken by Brischke (Beitr. zur Parth. a. Arth. 

 p. 228). The $ of Eriocampa adiwibrata is known, but is 

 certainly very rare. The same remark holds good with 

 HeinicJiroa alni, Selandria straj?iinepes, and others. 



It would be of great interest to prove if species like Plem. rufa 

 would produce females without the aid of the male. I am 

 anxious to investigate this subject, and should be greatly obliged 



for larvae of the species noted above. 



« 



31 Willowbank Crescent, Glasgow, 19th August, 1877, 



