17 

 Insect Orders 



The insects are a very extensive and diverse class of animals and they 

 affect man in many ways. Over 700,000 species have been described 

 from all parts of the world. Because of this it is worth while to survey 

 some of the more important orders of this group. Some of the lesser 

 known orders are omitted and, of course, all of the different kinds of 

 insects within the orders listed are not given. Nevertheless, this survey 

 includes the order names, the outstanding characteristics of the orders, 

 and a list of interesting features of insects commonly encountered by the 

 average person. Scientific names are given for the orders, but common 

 names are used for smaller groups. 



Order — Thysanura 



This order contains very primitive insects known as bristletails, fish- 

 moths, etc. They have no wings and no metamorphosis. They have 

 rudimentary appendages on the abdominal segments which suggests that 

 they are related to the annelid worms. They have biting mouth parts. 

 The silverfish is covered with silvery scales and has three long ap- 

 pendages, called cerci, on its posterior end. These insects live on the 

 starch in clothing and book bindings and may also eat paper. They 

 often do considerable damage to stored books, papers, and clothing 

 before their presence is discovered. 



Order — Collembola 



This order contains the springtails. Superficially they resemble the 

 Thysanura in lacking metamorphosis and wings. They were formerly 

 placed in the same order which was known as the Aptera. Members 

 of this order may have biting or sucking mouth parts. Springtails are 

 quite a nuisance to maple syrup producers because they often land in 

 the syrup buckets hanging on the trees. Some of them are known as 

 snow fleas because they emerge from their winter hibernation so early 

 that they often fall in the snow in vast numbers. They have a spring- 

 ing organ on the underside of the fourth segment of the abdomen. 



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