The British Guiana Museum. 239 
into the pupa, surrounds itself with a case or " cocoon'' 
of minute delicate threads, and from these the silk of 
commerce is derived. After a period of rest, the pupa 
changes into the fully developed inseft or imago. In the 
three orders of the Cicadas and Bugs, the Grasshoppers, 
and the Dragon-flies, the metamorphosis is incomplete ; 
in these, the larva has the form of the adult inse6t, but is 
destitute of wings. By the outgrowth of the wings 
(which, in inserts, are simply the lateral extensions of the 
second and third joints of the thorax), the adult form is 
reached. In the remaining insefts, which are wingless, 
there is no metamorphosis, the larva differing from the 
adult only in size. 
Among the butterflies and moths (Lepidoptera) , forms 
easily recognised by the hairs or scales on the wings, 
are to be seen the gorgeously coloured blue butterflies 
(Morpho), with their variously-marked, brown underwing; 
the pale grey and yellow, long-tailed forms with black 
markings (Papilio) ; the beautiful Dido (Cethosia) with 
its pale yellow green areas — quickly destroyed by light — 
and with its curiously-shaped pupae, brilliant during life 
with mirror-like areas ; the fairy-like diaphanous forms 
(Hoetera) ; the vividly-coloured, black and golden green 
striped, and tailed moth (Urania) ; the large dark-grey 
or ashy-black moths (Erebus) variously marked ; the 
different forms of the narrow-winged hawk-moths ; and 
an interesting series of the Attacus silk-moth (Attacus 
aurata), shewing the eggs, the caterpillar, the cocoons, 
the corded silk from the cocoon, the chrysalis, and vari- 
ous sizes of the fully developed imago. In many other 
examples different stages of the inserts are also shewn. 
Among the beetles (Coleoptera) , forms distinguished by 
HH 2 
