30 BRITISH GALLS 



bears from two to five sharply pointed spines. Fig. 7 

 depicts the young state of the smooth pea gall caused by 

 RhodiUs eglanteriae. This gall is frequent in August and 

 September. It is usually situated on the upper surface of 

 a leaflet, occasionally it appears on a sepai or on the stem. 

 It becomes brown or reddish towards maturity. Fig. 8 

 shows a section of a gall with the larval cavity in the centre, 

 and cells of inquilines around it. Fig. 9 is an enlarged view 

 of the larva ; Fig. 10 the female insect, magnified. The male 

 is very similar, but the abdomen is darker. 



The little Burnet-leaved Rose is frequently attacked by 

 Rhodites spinosissima. The galls occur on the stem, leaves, 

 petioles, and flower buds. They are green at first, assuming 

 a pretty red tint at maturity. Isolated ones are either ovoid 

 or reniform ; they frequently occur in conglomerated hard 

 woody masses of various shapes. The male of R. spinosissima 

 is rare. Cameron figures the female, remarking that he 

 had never seen her consort. Many inquilines and parasites 

 have been bred from all the Rhodites galls. 



II. GALLS ON THE OAK 



The great point of interest in connexion with many of the 

 Cynipidae of the Oak is the alternation of parthenogenetic 

 and sexual reproduction. 



Parthenogenesis, as defined by Von Siebold in 1856, is 

 the power possessed by certain female animals of producing 

 offspring without sexual union with a male. Bonnet, as early 

 as 1745, observed the production throughout the summer 

 of numerous generations of female yet fertile Aphides, 

 Hartig carried out extensive breeding experiments with 

 Oak gall- wasps about 1840, and demonstrated the existence 

 of numerous species, in which only females exist. Bassett, 

 in 1873, suspected that the parthenogenetic generation of 

 these is followed by a sexual one. Two years later, Dr. Adler, 

 who was quite unaware of Bassett 's work and surmises, 

 solved the problem by careful experiments with wasps of 



