INS ECT ORDERS 245 



Order — Isoptera 



These are the termites. The order name means equal wings, and 

 they have two pairs of membranous wings of equal size when they have 

 wings at all, but there are many generations that never have wings. 

 They have gradual metamorphosis and biting mouth parts. Their sole 

 item of diet consists of wood. Wood is composed mainly of cellulose 

 which cannot be digested by the majority of animals, and it would seem 

 that the termites would not fare so well on it. However, they have 

 protozoans living in their intestine that secrete enzymes that can digest 

 the cellulose on which both the protozoan and the termite live. This 

 is another example of symbiosis, for the protozoan receives protection 

 and the chewed up food to eat while the termite gets the wood digested 

 and can exist on this abundant material without much competition from 

 other insects. Their bodies are soft, possessing little pigment which 

 makes them quite sensitive to light, and so they seal any openings that 

 would allow light or dry air to reach their tunnels in the wood. 



In the tropics they are extremely destructive; so much so that in 

 some places houses cannot be constructed of wood. They are quite com- 

 mon in most of the southern states and seem to be extending their habitat 

 as far north as the Canadian border. 



They are social insects with an organization of tasks somewhat like 

 the honeybee. There is a single queen and many workers of both sexes. 

 Each year a winged generation is produced with pigmented bodies ; these 

 fly out of the nest, mate, and establish other colonies. 



Order — Dermaptera 



These insects are commonly called earwigs due to the mistaken notion 

 that they crawl into the ears of sleeping persons and bore into their 

 brains to cause death. Some are without wings, but those that have 

 them have a leathery front pair and a membranous hind pair that are 

 folded both lengthwise and crosswise to fit under the front pair. The 

 metamorphosis is gradual, and the mouth parts are for biting. There 

 are a pair of forceps-like cerci at the posterior tip of the abdomen. They 

 feed on plants and do considerable damage where they are abundant. 



Order — Coleoptera 



This is by far the largest order of insects — it includes those insects 

 known as beetles. The front wings are horny and serve as wing covers 

 for the membranous hind wings which fold up underneath. When fly- 



