INTRODUCTION. 13 



two-winged insects have a pair of small knob-like 

 threads behind the anterior pair of wings ; they have 

 been termed halteres or balancers, and are generally 

 regarded as the rudiments or representatives of the 

 hind wings. Mr. Lowne is inclined to think that the 

 function of these modifications of the posterior wings 

 is auditory ; he imagines he has discovered within 

 them certain corpuscular bodies, which he considers 

 to be otoconia. The membranous wings of butterflies 

 and moths are covered with numerous flattened scales 

 of various forms and exquisite beauty ; hence the name 

 of the order Lepidoptera from Xett/c: a scale, and Trnpov 

 wing ; while those of many others are simply clothed 

 with numerous small hairs. 



The abdomen, as has been said before, consists of 

 nine segments, but these are not always distinct ; it is 

 regarded as consisting of two portions, the abdomen 

 proper, and the post-abdomen, the latter of w^hich is 

 supposed to be marked by indications of three segments 

 between the generative outlet and the terminally 

 situated anus. The abdomen proper never carries 

 articulated appendages, with — so far as is known at 

 present — the single exception of the Sinrachtha Eury- 

 medusa, a beetle, which carries a pair on the third, 

 fourth, and fifth abdominal segments; the post- 

 abdominal segments, however, frequently carry ap- 

 pendages, as the thick bristles of the cockroaches, the 

 tubular appendages of the aphides, the forceps of the 

 earwigs. 



The organs of motion are localized in the thorax, the 

 vegetative in the abdomen. 



The accompanying woodcut will give the reader a 



