ON THE ORIGIN AND [CHAP. 



Coleoptera, from which, however, they differ in 

 their transformations. Fabricius, Olivier, and Latreille 

 regarded them as Orthoptera ; but Dr. Leach, on 

 account of the structure of their wings, considered 

 them as forming the type of a distinct order, in which 

 view he has been followed by Westwood, Kirby, and 

 many other entomologists. 



The Thysanoptera, consisting of the Linnaean genus 

 Thrips, are minute insects well known to gardeners, 

 differing from the Coleoptera in the nature of their 

 metamorphoses, in which they resemble . the Orthop- 

 tera and Hemiptera. The structure of the wings and 

 mouth-parts, however, are considered to exclude them 

 from these tw r o orders. 



The Trichoptera, or Caddis worms, offer many 

 points of resemblance to the Neuroptera, while in 

 others they approach more nearly to the Lepidoptera. 

 According to Westwood, the genus Phryganea " forms 

 the connecting link between the Neuroptera and Lepi- 

 doptera." 



The last of these small aberrant orders is that of 

 the Aphaniptera, constituted for the family Pulicidas. 

 In their transformations, as in many other respects, 

 they closely resemble the Diptera. Strauss Durck- 

 heim indeed said that " la puce est im diptere sans 

 ailes" Westwood, however, regards it as consti- 

 tuting a separate order. 



As indicated by the names of these orders, the 

 structure of the wings affords extremely natural and 

 convenient characters by which the various groups 

 may be distinguished from one another. The mouth- 

 parts also are very important; and, regarded from 



