PREFACE. XV11 



could not discover such a difference in their appearance, as 

 would have led me to suppose them in the larvae state ; 

 the antennae and legs were much thicker in proportion to the 

 bulk of the whole body, than when full grown : in fact they 

 bore pretty much the same resemblance to the mature 

 insect, that a lamb bears to a ewe, being ill- proportioned 

 in the legs, &c. In point of activity, however, they much 

 exceeded the adult, and moved with a degree of rapidity 

 not usual to such insects, at least to the Family Pediculidae. 

 In many species as will subsequently appear, a very great 

 difference in colour and markings is observable after each 

 moult, so much so, that unless an opportunity of examin- 

 ing a series of all sizes and ages occurs, the identity of 

 the species would scarcely be conjectured. Lastly, Mr. 

 Westwood, in his able and elaborate Introduction to the 

 Modern Classification of Insects, holds the same opinion as 

 Dr. Leach, that these animals undergo no metamorphosis, 

 and from his investigations having induced him to consider 

 a distinct metamorphosis as the fundamental characteristic 

 of the class Insecta, he consequently excludes the Lice 

 (Anoplura), as well as the Spring-tailed Insects (Thysa- 

 nura), from the class Insecta altogether : I could have 

 wished Mr. Westwood had given his views as to what class 

 he considered they ought to belong ? With respect to the 

 Classification and Natural History of this remarkable order 

 of parasites, although both have been neglected, there is 

 not such diversity of opinion concerning the former as there 

 is obscurity and paucity in the latter. In the earliest at- 

 tempt at the classification of animals with which we are 

 acquainted, that of Aristotle (330, B.C.). there is a division 

 of the insects, "Evrojua, into two orders, deduced from the 

 presence or absence of wings, whence we have "Evro/za 

 TTrtXwra, and "Evro^a aVre/oa ; divisions considered so per- 

 fectly natural as to have been retained by nearly all suc- 

 ceeding writers. Though the peculiar insects with which 



