1917] Parthenogenesis in the Pear-slug Saw-fly 331 



and hawthorn saw-fly leaf-miner, Proj'enusa collaris Mac- 

 Gillivray, by Parrott and Fulton. j In this regard they give 

 the following: "Out of doors the females appeared in larger 

 numbers at a somewhat earlier period than the males, but 

 judging from collections taken at irregular intervals it does not 

 appear that marked numerical differences existed between the 

 sexes. To all appearances the adults copulated freely. In one 

 breeding cage, containing no males, two females made their 

 appearance, and these were isolated and supplied with cherry 

 twigs to induce oviposition. This they did, and five days later 

 three eggs hatched. This experience suggests that fertilization 

 is not absolutely necessary for the development of the eggs and 

 also indicates that parthenogenesis may occur, although it is 

 perhaps not an important factor in the life of the species. " 



Experiments at the Iowa Station. 



Webster in his bulletin states that parthenogenesis probably 

 occurs in the pear-slug saw-fly, but that it had not been satis- 

 factorily proved. However, he showed that virgin females 

 would deposit eggs and that these eggs would hatch; yet none 

 of the larvae hatching from parthenogenetic eggs was reared to 

 maturity. In regard to these experiments, Webster states: 

 "Both Mr. Ness and Mr. McCall confined virgin female saw- 

 flies in insectary. cages and obtained eggs from them. Some 

 of these eggs hatched, but the larvae were weak and in no case 

 did they live more than a few days. None reached the second 

 stage." These experiments seemed to show that there was not 

 a complete normal parthenogenesis like that which exists in 

 the plant lice, or in fact in the case of some of the other species 

 of saw-flies, but a type similar to that known to exist in the 

 silk worm, where only a few unfertilized eggs hatch, and the 

 issuing larvae never reach maturity. 



Breeding Experiments Carried on by the Writer. 



During the month of May, 1913, while rearing the black 

 cherry aphis, Myzus cerasi Fab., as food for Coccinellidae, the 

 life histories of which I was studying, three females of Caliroa 

 cerasi emerged in the aphid breeding cages. These breeding 



tParrott, P. J., and Fulton, B. B. The Cherry and Hawthorn Sawfl}^ Lea-j 

 Miner, Bui. Xo. 411, New York Agric. Exp. Sta. (1915). 



