THE SPURGE MOTH. 293 



continually spin as they crawl along. But no caterpillar is 

 known which is gifted with the instinct of cutting off leaves 

 and bringing them home for food, and we may therefore infer 

 that the leaves in question were growing on the branches, and 

 that the nests had been purposely spun round them. 



These are, however, one or two species of British insects 

 belonging to the lepidoptera, which do cut off leaves and use 

 them for the construction of the cocoon, though they do not 

 employ them for food. These insects are moths, belonging to 

 the genus Acronycta, and popularly called Spurge Moths, on 

 account of the plant on which they reside. One of these species 

 makes a. really curious pensile cocoon from the leaves of the 

 cypress spurge {Euphorbia cyparissias), rather a scarce perennial 

 plant about a foot in height, growing about woods and the 

 borders of the fields. The leaves of the stem are lance-shaped, 

 and those of the branches almost linear, like grass blades, and it 

 is of these lattei; that the insect makes its habitation. 



About October, the caterpillar begins to make its house, and 

 does so in a very curious manner. Detaching a leaf from a 

 branch, it fastens one end to the stem, and then bends the leaf 

 so as to form a loop, and fastens the other end in a similar 

 manner. A number of the leaves are placed nearly parallel to 

 each other, so that when they are firmly woven together they 

 form a bag-like cocoon, fixed to the stem of the plant by one 

 side, and being upright like that of the bumet motL Its tex- 

 ture is, however, very unlike that of the burnet, being loose, 

 almost wholly composed of vegetable matter, and comparatively 

 flimsy. 



It has well been remarked that the strength, or at all events, 

 the weather-resisting power, of a cocoon depends upon the length 

 of time which is occupied by the insect in undergoing its trans- 

 formation, those creatures which only spend a few weeks in the 

 pupal state being content with a mere web or hammock of silk, 

 while those which pass the winter in the pupal condition make 

 habitations which are comparatively substantial. 



This rule, however, is not without its exceptions, as we find 

 the pupae of several butterflies, the' common cabbage butterfly, 

 for example, merely hung against walls, &c., without any protec- 

 tion around them. Instinct leads them to choose such spots as 



