492 Habits of a Cynipideous Insect, 



How these galls are formed is a question not yet solved ; 

 although some ingenious, and some, even among the latest, 

 very untenable theories have been proposed for its solution. 

 Into this question, however, I do not here propose to enter. 



In the modern systems of insects, we find this family, not- 

 withstanding its habits of feeding, in the larva state, upon the 

 vegetable matter contained in galls, introduced into a series of 

 families, all of which are parasitic upon other insects in the larva 

 state. This, at first sight, and with the knowledge only of 

 facts hitherto recorded, appears very unwarrantable, in respect 

 to the natural relations of these groups; and yet, when we 

 examine the general structure of the gall flies (and more par- 

 ticularly the neuration [nerving] of the wings, articulation of 

 the antennae, arid peduncled abdomen), it is very evident that, 

 notwithstanding their diversity in habits, the gall flies are 

 more nearly allied to these parasitic families than to any other 

 hymenopterous insects : whilst the facts subsequently detailed 

 establish the correctness of these views, and open an interest- 

 ing field of enquiry into the natural relations of affinity and 

 analogy of the aberrant hymenopterous groups; into which, 

 as being too dry for more general readers, I also refrain froril nl; 

 enteringj jniJ jglid// bsabfittB zudi ^nhto 'ic te C9 * 



In the autumn of 1832, Mr. Stephens [Entomologice Bri- 

 tanniccB cultorum magister) mentioned to me, that having, 

 during the preceding summer, placed a quantity of aphides, 

 which appeared to be ichneumoned (to coin the term), in a 

 pill-box, he found, on examining it some months afterwards^'!* 

 a quantity of small dead gall flies ; the interior of the bodies 

 of the aphides having been entirely consumed. 



Being anxious to obtain farther particulars relative to so 

 interesting a point of natural history, I carefully examined the 

 rose lice for some time, in the early part of last summer 

 (1833) ; and, on the 20th of June, I was rewarded by observ- 

 ing a small cynipideous insect, similar to Mr. Stephens's, in 

 the act of depositing an egg in the body of an aphis, con*-uod 

 siderably larger than itself. So intently was it occupied, that 

 I was enabled to cut off the sprig, to carry it into my study, 

 and to examine the insect, when there, with a lens of a quar- 

 ter of an inch focus. On its withdrawing its ovipositor from 

 the body of the aphis, upon which it was at the time engaged 

 in depositing an egg, it had not far to travel to find another 

 nidus for the reception of another of the germs of its future 

 progeny, since it took its station on the back of the aphis next 

 to the one from which it had just dismounted. I observed that 

 it invariably placed itself with its head looking towards the 

 head of the aphis, even if it ascended in the contrary direc- 

 tion. When once mounted, it kept its station as firmly as the 



