A FOREIGN INVASION OF ENGLAND 309 



times for long distances across country ; but their 

 prospective partners are almost always shyer and 

 more maidenly ; they hide under the leaves and 

 travel but short distances, considering it more lady- 

 like to stop at home and wait for suitors than to 

 go out and seek them. They are not new women. 

 Indeed, so great is their modesty that they often 

 hide in holes in the ground to escape observation ; 

 and they usually alight on the earth, as their colour 

 is blackish, and they are there less exposed to the 

 attacks of birds and other enemies than on the 

 green foliage. It is a noticeable fact in nature that 

 many species of animals seem thus to know in- 

 stinctively the colours with which their own hues 

 will best harmonise, and to poise by preference 

 on such colours ; many dappled or speckled insects, 

 for example, resting with folded wings on the 

 dappled and speckled flower-bunches of the carrot 

 tribe, while green insects affect rather green leaves, 

 and brown or black insects come to anchor on the 

 soil, which best protects them. This is not quite 

 the same thing as what is called protective colour- 

 ing, such as occurs in desert animals, most of 

 which are spotted like the sand, or in the fishes 

 and crabs which frequent the sargasso-weed in the 

 Sargasso Sea, all of which are of the 'same pale 

 lemon-yellow tint as the seaweed they lurk among ; 

 for this case of the Hessian fly includes a delibe- 

 rate choice of ingrained habit. The insect has 

 many objects of many different colours spread 

 about in its neighbourhood, but it habitually selects 

 as its resting-place those particular objects which 



