94 INTRODUCTION. 



ing to black. Occasionally, however, they are of 

 brighter hues ; that of Geometra alniaria is bluish ; 

 that of the dark crimson under wing (Catocala 

 sponsa), lilac; and that of the common Magpie- 

 moth (Abraxas grossulariata), a species remarkable 

 for the similarity of its colours through all its diffe- 

 rent stages, is ornamented with alternate rings of 

 black and yellow. 



The security which arises to the pupse of butter- 

 flies from being hung out of the way of danger, is 

 provided for among moths, by enveloping them in 

 a dense tissue of silk or extraneous substances, and 

 frequently by burying them in the earth or in the 

 interior of plants. This covering of the chrysalis, 

 of whatsoever materials it is composed, is named the 

 cocoon. Silk is almost always used in its composi- 

 tion, and in very many cases it is the only substance 

 employed. In structure, texture, and many other 

 properties, cocoons vary extremely. Sometimes the 

 caterpillars content themselves with filling a certain 

 space with threads, crossing each other in various 

 directions, and leaving many voids between them : 

 in the centre of this loose web the chrysalis is placed. 

 In other instances the fabric is more closely woven, 

 but still sufficiently open to allow the chrysalis to 

 be seen, and apparently inadequate to protect it 

 from the weather. In such cases, however, addi- 

 tional shelter is often obtained by drawing round 

 it a few of the leaves among which it is usually 

 placed. Many hairy larvae increase the compactness 

 of their cocoons by stripping their own bodies and 



