A HISTORY OF CORNWALL 



CYNIPIDAE 

 Gall-flies 



Most of the Gall-flies (Cynipidae) lay their eggs in the meristematic tissue of plants, chiefly, 

 however, on the oak, and a secretion apparently from the larva itself causes an exuberant local 

 growth of tissue that results in the formation of a gall. The oak apple, the oak spangle, the 

 marble gall, and the moss-like bedeguar on the rose are familiar examples of such pathological 

 growths. Some of the gall-flies, however, like the members of the genus Synergus are inquilines or 

 guest-flies, laying their eggs in the galls formed by the gall-makers either during or subsequent to 

 the growth of the gall. The typical cynipid gall-maker presents the remarkable anomaly of an 

 alternation of generations, the autumn-formed gall producing females only, which by parthogenetic 

 birth give rise to a spring brood of males and females. These last, as a rule, are only about one- 

 third the size of their parent, and are very dissimilar in form of gall and in general appearance from 

 the generation from which they arise. For thirteen species the galls both of the agamic and of 

 the sexual generation have been found in Cornwall, and in the majority of cases the corresponding 

 ' flies,' together with various inquilines and parasites, have been successfully raised. The process 

 with many of the autumn-formed galls is long and tedious, some of them not appearing till the 

 third year. 



Even more remarkable than this alternation of generations displayed by many of the species 

 is the apparently complete absence of the male in Cynips Kollari and in Andruw albopunctatus. So 

 far as can be ascertained, these species are propagated by perpetual parthenogenesis as only the 

 agamic forms are known. 



Till five years ago this section of the Hymenoptera had received no attention in the county, 

 but in the autumn of 1900 an appeal to the members of his agricultural class at the Technical 

 Schools, Truro, resulted in a plentiful supply of galls of many kinds being brought in to the writer. 

 To Commander Arthur Rogers, R.N.R., and to Mr. William Borlase, his thanks are specially 

 due for the valuable services these skilled collectors so freely rendered in diligently searching out 

 many of the rarer forms. 



The accompanying list of Cynipidae contains in all thirty-seven species. Where both broods of 

 those that exhibit alternation of generations are known from actual observation to occur in the 

 county, the specific names by which the two generations are still distinguished are bracketed 

 together, the agamic generation in each case taking precedence : 



Rhodites eglanteriae, Htg. 



rosae, L. 



spinosissimae, Gir. 

 Aulax glechomae, Htg. 



hypochaeridis, Kieffer 

 Xestophanes potentillae, Vill. 

 Periclistus caninae, Htg. 



Brandti, Ratz. 

 Synergus melanopus, Htg. 



rheinhardi, Mayr 



radiatus, Mayr 



fascialis, Htg. 



thaumacera, Dal. 

 - nervosus, Htg. 



Diastrophus rubi, Htg. 



Andricus ostreus, Gir. 

 ( fecundatrix, Htg. 

 { pilosus, Adler 



(Andricus globuli, Htg. 



\ inflator, Htg. 



f radicis, Htg. 



\ trilineatus, Htg. 



' sieboldi, Htg. 



\ testaceipes, Htg. 



corticis, L. 



collaris, Htg. 



curvator, Htg. 



autumnalis, L. 



ramuli, L. 



quadrilineatus, Htg. 

 ( callidoma, Gir. 



( cirratus, Adler 



glandulae, Schenck 



solitarius, Fonsc. 



albopunctatus, Schlecht 



Cynips Kollari, Htg. 

 JTrigonaspis renum, Gir. 

 \ megaptera, Pz. 

 (Biorhiza terminals, Fabr. 

 ( aptera, Fabr. 



Dryophanta folii, L. 



divisa, Htg. 



longiventris, Htg. 

 'Neuroterus lenticularis, 



Oliv. 

 , baccarum, L. 



fumipennis, Htg. 



tricolor, Htg. 



laeviusculus, Schr. 



albipes, Schr. 



numismatis, Oliv. 



vesicatrix, Schlecht 



ENTOMOPHAGA 



Ichneumons and their Allies 



The Ichneumon flies and their allies constitute Nature's most powerful check on the excessive 

 increase of our insect population. Insects derive their sustenance very largely from the vegetable 

 kingdom, and the destruction of all vegetation through the undue multiplication of phytophagous 

 larvae like the Lepidoptera would be an ever-present danger but for the singular habits of this great 

 family, every member of which is a parasite, dwelling in most cases in the body of a larval host, 

 appropriating the nutriment the latter digests, and ultimately causing its death. The female 

 ichneumons, as a rule, insert their eggs into the bodies of the selected larvae, and the resulting 

 legless maggots during their development lie motionless in the dorsal half of their host, and either 



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