The Orders of Insects i6i 



allied to one another in spite of considerable differ- 

 ences in the nature of their wings and in the details 

 of their life-histories. The Flies whose hindwings are 

 reduced to stalked knobs form an easily recognised 

 order (Diptera), as do the Beetles (Coleoptera) with 

 their horny forewings and powerful biting jaws. 

 Flies and Beetles agree with the Lepidoptera in passing 

 through a passive pupal stage. This character of the 

 life-history is shared also by the insects of another 

 universally recognised order, the Hymenoptera, which 

 are distinguished by the possession of four clear 

 net-veined wings (the hind-pair being always much 

 smaller than the front pair), and biting mandibles. 

 The leading features of the Orthoptera have already 

 been mentioned. A few families of small wingless 

 insects, Springtails and Bristletails, with jaws with- 

 drawn into the head capsule, or with abdominal limbs 

 present throughout life, make up the orders Col- 

 lembola and Thysanura. 



The vast majority of the families not included in 

 the orders hitherto mentioned agree in the possession 

 of four membranous, net-veined wings and biting 

 jaws. On this account they have often been regarded 

 as forming a single order, the Neuroptera (3). But 

 such divergence is to be found among these insects 

 in their life-histories and in many details of their 

 structure, that by most modern students they are 

 divided into six or seven different orders (96, 97). 

 Objection may be taken to whichever of these two 

 courses be followed. The difference between a 

 Termite and a Dragonfly is less marked and con- 

 spicuous than that between a Moth and a Beetle, 

 and therefore it may be urged that the same term 

 should not be used to define such uneven distinctions. 

 But we have seen that all the terms used in insect 

 classification must bear values differing in different 



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