HABITATIONS OF INSECTS. 



383 



found in galls besides grubs of different kinds, wbich they ra- 

 tionally conceived to spring from eggs, were chiefly at a loss 

 to account for the conveyance of these eggs into the middle 

 of a substance in which they could find no external orifice. 

 They therefore inferred that they were the eggs of insects 

 deposited in the earth, which had been drawn up by the roots 

 of trees along with the sap, and after passing through dif- 

 ferent vessels had stopped, some in the leaves, others in the 

 twigs, and had there hatched and produced galls ! Redi's so- 

 lution of the difficulty was even more extraordinary. This 

 philosopher, who had so triumphantly combated the absurd- 

 ities of spontaneous generation, fell himself into greater. Not 

 having been able to witness the deposition of eggs by the 

 parent flies in the plants that produce galls, he took it for 

 granted that the grubs which he found within them could not 

 spring from eggs : and he was equally unwilling to admit their 

 origin from spontaneous generation, — an admission which 

 would have been fatal to his own most brilliant discoveries. 

 He therefore cut the knot, by supposing that to the same ve- 

 getative soul by which fruits and plants are produced is com- 

 mitted the charge of creating the larvae found in galls ! ^ An 

 instance truly humiliating : hoAV little we can infer from a 

 man's just ideas on one point, that he will not be guilty of the 

 most pitiable absurdity on another ! 



Though by far the greater part of the vegetable exeres- 

 t^ences termed galls are caused by insects of the genus Cynips, 

 they do not always originate from thi« tribe. Some are pro- 

 duced by weevils of diflerent genera and species. Thus those 

 on the roots of kedlock (Sinapis arvensis) I have ascertained 

 to be inhabited by the larvae of Nedyus contractus and assimilis. 

 From the knob-like galls on turnips, called in some places the 

 ambury, I have bred another of these weevils ( Curculio pleu- 

 rostigma Marsh., Rhynchcenus sulcicollis Gyll.), and I have 

 little doubt that the same insects, or species allied to them, 

 cause the clubbing of the roots of cabbages.^ It seems to be 



1 De Insectis, 233, &c. 



2 Mr. Westwood informs us that he has not detected any other larvee in the 

 clubs at the roots of cabbages than those of a species of Muscidce {Anthomyia 

 brassiccB), and which had evidently been produced from eggs laid in crevices of 

 the already formed clubs. 



