214 STATES OF INSECTS. (Larva.) 
pterous tribes of Bombycide and Noctuide ; but a few 
Geometers (Hipparchus papilioniarius, Minea lactearia, 
&c.); most of the Hymenoptera; some Coleoptera, as 
certain of the weevil tribe (Hypera Arator, Rumicis), 
and those brilliant beetles frequenting aquatic plants 
constituting the genus Donacia; the Neuropterous 
genera Hemerobius and Myrmeleon ;-Mycetophila and a 
few others in the Diptera; and Pulex in the Apha- 
niptera—fabricate coverings of the same material. In 
all, with the exception of Myrmeleon and Hemerobius 
(and perhaps Hypera Rumicis, &c.?), which have their 
spinning apparatus at the extremity of the abdomen, the 
silken thread employed in forming these coverings pro- 
ceeds from the middle part of the under-lip, as before 
explained ; and is in fact composed of two threads gum- 
med together as they issue from the two adjoining ori- 
fices of the spinner. 
Of the Jarvee which inclose themselves in sz/k, the 
most familiarly known is the silk-worm: the cocoon of 
this consists exteriorly of a thin, transparent, gauze-like 
coating, through the interstices of which can be seen an 
inner, smaller, oval ball of a more close and compact 
texture. The whole is in fact composed of one single 
thread, but arranged in two distinct modes. To form 
the exterior envelope, which is merely the scaffolding 
by means of which the inner and more solid covering is 
constructed, the caterpillar, after fixig upon a space 
between two leaves or twigs or angles suitable for its 
purpose, begins by glueing one end of its thread to one 
of the adjoining surfaces. This thread it next conducts 
to another part and then fastens, repeating this process 
and interlacing it in various directions, until it has sur- 
