The Scottish Naturalist. 33 



had been with any male. Those females were put on bushes of 

 Rosa canina: on May loth, 12 wasps ;^ May 13th, 16 wasps; May 

 26th, 10 wasps ; June 2cl, 6 wasps, — together, 44 wasps. Of those 

 26 wasps were observed in the act of oviposition, and the twigs were 

 marked with a thread around each. The first formation of a gall 

 was observed June 5th, and in all only nine twigs formed galls ; 

 giving the positive result that unimpregnated eggs had developed. 

 The experiment was tried again for the purpose of having surer 

 results by repetition, and to investigate why the first experiment 

 was without result in so many cases. In 1874 there were put, 

 June 2 2d, on rose-bushes 8 wasps, 4 of which were observed in 

 oviposition, none producing galls ; June 23d, of 10 wasps, 4 ob- 

 served in oviposition, 2 producing galls ; June 27th, of 12 wasps, 

 5 were observed in oviposition, producing 3 galls. 



'^ Of the 13 wasps observed in the act of oviposition, 4 were dis- 

 sected, and the receptaculum seminis stated to be entirely empty 

 (without spermatozoa). Every one of the wasps spoken of was 

 carefully observed and not lost sight of till the wasp had begun 

 the oviposition, in which act some persevered for more than 24 

 hours. Of course observation was not followed through this 

 whole time, but every few hours it was again observed that the 

 wasp was continuing the oviposition. The five produced galls 

 were in November preserved for the experiment of the following 

 year. In the spring of 1875 there were raised from them 35 

 wasps, all females, and a large number of parasites. These 

 wasps were put again on rose-bushes as soon as they appeared on 

 May 26th, June 2d, 5th, 7th, and oviposition observed on 1 1 twigs. 

 After II days some of the eggs were examined, and the embryo 

 found in different stages of development (more details are given). 

 Of the 1 1 twigs 6 produced galls, out of which were raised in spring, 

 1876, 28 wasps, all females. Those wasps were put on rose- 

 bushes June 26th, July 2d, July 4th, and oviposition observed on 

 13 twigs, which produced 8 galls. Therefore, through three years 

 parthenogenetic propagation was observed. The objection that 

 in experiments thus made in the open air oviposition could have 

 been made on the same twigs by other wasps, cannot be refuted 

 directly; but if it has been noticed so many times that only galls 

 were produced in the observed and marked places, I believe it 

 is allowable to conclude that none except the observed oviposi- 

 tion had been made. 



1 "Wasp" is used here to designate the perfect gall-insect or fly, and is 

 not restricted to a species of Vespa as is usual amongst us. — Ed. ' Sc. Nat.' 



C 



