Coloration and Development of Insects, 73 



become full-fed they separate, and each seeks a suitable 

 hiding-place. They do not pupate apparently on their natal 

 tree, but descend it to go in search of another, up whose 

 trunk they march, and spin their cocoons in crevices. I 

 have found them doing this on trees — firs, beeches — 

 many yards' distance from any poplars. Last September I 

 found one far from the food-plant, about six feet up on the 

 trunk of a beech, where it was readily noticed by its gaudy 

 colour. It was put into a tube, and in half an hour had 

 begun to spin its cocoon. Here, then, we have the reason 

 for the gaudy coloration acquired at the last moult ; it is to 

 make it more conspicuous than it would be if it had 

 retained the green which it had when feeding. The species 

 of this genus spin an irregular, thin, semi-transparent 

 cocoon, which is spun either in chinks in the bark, or in 

 stems of herbaceous plants. Hence they may have to go 

 some distance before a proper place is met with. 



b. Dimorphic larvae. — The question of dimorphic larva3 

 with the Tentliredinidoi is one well worthy of attention. 

 The subject is at present somewhat obscure, for although I 

 have bred forms, which I cannot separate in the perfect 

 state from diifcrently-coloured larvae, and might therefore 

 conclude that they were dimorphic larvre of the same 

 species, yet further observation might show that in reality 

 they were distinct species. I am not now referring to 

 such cases as Lophyrus similis and L. pini, and Nematus 

 cadderensis. Cam. and N. croceus, Fall, {fidvus H.) ; for 

 although in these two cases the perfect insects cannot be 

 separated by any distinct characters, yet the larvas are so 

 different in form, coloration, and habits, as to preclude 

 the idea of their being dimorphic larvce of the same 

 species. I am alluding to such forms as I have described 

 elsewhere,* where larvoe differently marked (but still 

 having some common characteristics) produced images 

 which cannot —or, at any rate, I cannot, nor can Herrn 

 Brischke and Zaddach, as they inform me in litt. — be 

 satisfactorily separated. Nematus caprece, Pz., has two 

 forms of larvae : one, the common type, green, with 

 white lines ; and a much rarer form, which is reddish, 

 but with the same markings as the other. Both feed 

 on the same food-plant (Carices) and in the same 

 locality. One or two species of Cimbex would appear 



* Fauna of Scot., p. 41, 



