96 



Mr. R. J. Ashton on the 



thick rib. This rib, when the insect unites its wings, passes 

 throujrh the narrow slit above mentioned, and thus catches and 

 is retained in the groove during the insect's fliglit. Of the efficacy 

 of this simple contrivance for the purpose in question, any one 

 may satisfy himself by the difficulty experienced in disengaging 

 the wings of one of these insects when united. I must not omit 

 in this place to mention the instance exhibited here of the perfec- 

 tion usque ad iniiim with which all the creations of Omnipotence 

 are endowed; for although the apparatus I have thus endeavoured 

 to describe is so minute as to require an exceedingly high micro- 

 scopic power to examine it, yet is the interior of the groove dis- 

 covered to be lined with a pubescence apparently similar to that 

 beneath the tarsi of many insects, doubtless principally for the 

 purpose of protecting the membrane of the wing from abrasion or 

 injury by friction whilst inclosed in it. 



The other form of the structure to which I have above alluded 

 is the following. In the insects so constituted, a small portion of 

 the anterior edge of the hinder wing is turned upwards, and from 

 it a simple corneous process projects backwards, the general form 

 of which is represented at fig. 8, as it occurs in the above men- 

 tioned insect, Ccntrotus cornutus. This process does not occur 

 upon the principal nervure of the wing which runs along the 

 anterior margin, but ratlier on the (generally narrow) portion of 

 membrane found anterior to that nervure, and quite at the edge 

 of the wing. This tooth or process of the posterior wing catches 

 into a corresponding recess formed in the hinder margin of the 

 under side of the anterior wing, the edge of which, at that point, 

 is bent down and reflected forwards, forming a small channel for 

 the reception of the above process. (Fig. 7.) I have ascertained 

 that tlie under side of the process above described is finely 

 dentated, and have little doubt that there is a corresponding in- 

 dentation in the recess, which considerably strengthens the union 

 of the parts when joined. 



The j)oint at which the wings unite is, in all cases that I have 

 examined, situated at the apical extremity of the hinder nervure 

 of the anterior wing, and where that wing possesses a membra- 

 nous piece at its extremity, as in Nolonccta, is just at the point of 

 division between the corneous and membranous points ; conse- 

 quently the point of union varies according to circumstances 

 connected with the form, &-c. of the wing, in some being pro- 

 portionably nearer to, and in others further from the base of the 

 wing. 



From the examination I have made amongst insects of this 



