THE EVOLUTION OF THE CATERPILLAR 621 



but they are interesting because they show that, however 

 far up the scale of progressive development the perfect insects 

 have risen, so long as the larvas live in surroundings which are 

 not subject to the influences of light, their outward appear- 

 ance does not change to any extent. 



Before passing on to consider the very varied forms which 

 come into the open, a departure which is comparatively unusual 

 in the Order, but leads very naturally from the subterranean 

 habit, may be given some attention. This is the case of the 

 wood-boring and leaf-mining species. The purpose of con- 

 cealment has, in this case, not been satisfied by approximation 

 of colour, and most of the leaf-mining species are of whitish or 

 indefinite coloration. They are, from the very nature of the 

 case, exceedingly minute, and the perfect moths are seldom 

 more than one-eighth to a quarter of an inch across the wings. 

 They are, however, exceedingly beautiful, and under the micro- 

 scope are seen to have elaborately patterned scales, often of 

 rich metallic colours, gold and silver being particularly pre- 

 dominant. The method of these tiny caterpillars is to con- 

 sume only the inner substance of the leaf, so that the tougher 

 outer coats, above and below, remain unbroken, and the 

 result of their operations is a pale marking, commencing as 

 a fine line, which wanders erratically about the leaf and grows, 

 like a river, as the miner increases in size. 



There is an incredibly large number of these minute moths, 

 the British species alone being approximately 200 to 300, and 

 practically all our commoner plants have one or more species 

 of miner devoted to them. Those who are interested in this 

 pigmy race, may study them readily enough by collecting the 

 mined leaves and preserving them in a jar (covered with a 

 sheet of glass) until the winged insects appear. 



Ill 



The wood-borers are comparatively few in number and in 

 this country are confined to the families Sesidece, Zenzeridce, 

 and Cossidce. Of the first family there are about a dozen 

 British species, all of which are remarkable for the fact that 

 their wings have very few scales upon them — they have a 

 striking resemblance to wasps, bees, and insects of other 

 orders. That they have diverged from the common ancestral 

 stock to a much less degree than the majority of Lepidoptera, 

 is perfectly obvious from their general appearance, and the 

 fact that their larvae are naked and whitish in colour and thus 

 conform more closely to the primitive type of grub, is addi- 

 tional evidence. In fact, when the whole of the circumstances 

 of this group are studied^ it seems passing strange that the 



