( cxvii ) 



an inherited structure like the spines at the apex of the elytra 

 in Uroplata already alluded to, then we should expect to find 

 indications of it in closely allied forms, but this is not the 

 case. If it is associated with some habit of the insect and is 

 useful, then it must be useful in more than one way, as insects 

 of totally different habits have it. And if, generally speaking, 

 it is a useful form of claw, then it is remarkable that so few 

 insects have developed it. 



Another point which suggests itself to one's mind is that 

 perhaps the reason why so few insects have developed complex 

 claws is that they are rendered unnecessary by the sticky 

 hairs or adhesive pads on the undersides of the tarsi. We 

 find, however, that many insects which have these sticky hairs 

 have also bifid or pectinate claws, such as Amphionycha, 

 Corynodes, Ctenochira, Pieris, Lycama and many others which 

 can walk on glass perfectly well. Among those which I have 

 tried on clean vertical glass I may as well just mention here 

 that all the Ichneumonidie, Trlchoptera, Tlneina, and all the 

 Diptera (except perhaps Tipula) could run freely on it, but the 

 Syrphidx were uucertain. Halictus and some other small bees 

 were fairly at home, but Bombus and Apathus were quite 

 helpless, as were also Colias and Vanessa. Adrastus, the little 

 Elaterid that I have mentioned among those with pectinate 

 claws, was very uncertain. 



Some insects when resting only touch the object they are 

 standing on with the extreme tip of the tarsus. I noticed 

 that when Fieris was resting on the glass it was holding on 

 only by the apex of the pulvillus which projected just beyond 

 the tip of the claws ; it needed a magnifying glass to see this. 

 Plusia gamma, which seemed to be holding, was found, when 

 looked at with a magnifying glass, to be slipping very slowly 

 all the time, but it kept its position by darting forward its 

 right foot, and when this had slid down some distance the left 

 one was shot forward, and so on. I have already alluded to 

 the necessity of taking into account the adhesive hairs. The 

 spines on the tarsi of fossorial Hymenoj)tera and other insects 

 must also not be forgotten. I should imagine that these 

 spines would act somewhat in the way of a thumb. When 

 settling on any object the claw would probably be the first 



H 2 



