List of the Insect Fauna of the County. 103 



the growth."" Hofmeister observed the same prmcixole when 

 he mamtained that the growth of the gall is due to the fact 

 that it encloses an active living grub ; ^^ but he has over- 

 looked those very obvious circumstances in which we find the 

 galls fairly formed and often well grown before the larva- state 

 of their legitimate inhabitants is reached. Here we fall back 

 on Hartig, who had already clearly demonstrated the absolute 

 growth of the curious pedunculate eggs of the Cynipid* and 

 other terebrant Hymenoptera.^^ Dr. Holhs gave a quotation 

 from Guibourt, which I here include/^ relative to the com- 

 mensalism between the active life of the gall and of the 

 gall-maker; and then continues, " With some reservation I 

 accept the theories of Hofmeister and Guibourt, with regard 

 to the origin and growth of the gall-nut, but I must introduce 

 a third element into their formation, which appears to have 

 been somewhat overlooked by these writers, and that is, the 

 active growth of the plant itself. "^^ This all-important 

 element had probably been understood, still it needs enun- 

 ciation. It is most certainly a fact that a gall is never 

 produced, except on those parts of a i^lant which are in 

 active growth and in full receipt of the sap-flow. It may 

 also, I think, be taken as a fact that the more active the 



11 'Flora of Berwick-upon-Tweed,' ii. 108. 



12 ' Die Lehre von der Pfanzenzelle,' p. 634. (Leipzig, 1867). 



13 ' Wiegmann's ' Ai^cliiv fiir Naturgeschichte,' iii., p. 151, pi. iv., 1837. 

 Germar's ' Zeitscluift fiir die Entomologie,' ii., p. 171) (1810), and iii., 

 p. 327, pi. i., figs. 5, 6 (1811). Also consult 'Over de Legboor van 

 Aphilothrix radicis, Fabr." By Dr. M. W. Beijerinck, in the ' Tijdschrift 

 voor Entomologie,' vol. xx., pp. 186—198, plates 11 and 12 ; 1876—7. 



i-i " Une autre observation qui est commune aux autres galles, c'est que 

 tant que I'insect y est enferme, la galle du chene tauzin offre une couleur 

 rougeatre et verdatre, et une surface luisante qui indiquent qu'elle 

 participe a la vie de I'animal ; tandis qu'apres sa sortie, elle prend une 

 couleur terne et grisatre et semble mourir." 'Histoire naturelle des 

 Drogues simi^les,' 1849 ; ii., 278. 



15 In a note on insect gall buds, Mr. A. Stephen Wilson, of Aberdeen, 

 under date May 15th, 1879, thus writes to 'Nature' (vol. xx., p. 55) :— 

 "The insertion of the ovipositor brings a medullary ray into action, 

 producing a tuberculated bud, and it is only the bud which the larva 

 feeds upon. The growth of a bud is an intehigible cause of the growth 

 of a gall, but we can infer nothing from the injection of a fluid." 



