INSECT 



3000 



INSECT 



openings in the side of the body, usually eight 

 pairs of them in the abdomen, which have 

 grates of stiff hair to keep out the dust. An 

 insect may be asphyxiated by coming in con- 

 tact with some- 

 thing greasy or 

 oily, if a film of 

 oil spreads over 

 its spiracles, air 

 openings. An in- 

 sect has no bony 

 skeleton ; its prin- 

 cipal nerve cord 

 extends along the 

 underside of the 

 body. Its brain, 

 because of the 

 many movements 

 controlled, is 

 complex. Its 

 heart is a pulsat- 

 ing tube of sev- 

 eral chambers, ex- 

 tending through NERVOUS SYSTEM OF AN 

 the insect's whole 



length. The blood, yellowish-white .or green- 

 ish, flows everywhere in the body without pass- 

 ing through arteries and veins; it nourishes 

 and purifies the whole system. An insect has 

 claws to use in climbing. From the ends of 

 hollow hairs which fringe the cushion between 

 the claws comes a sticky fluid which helps flies 

 to walk on glass or to travel with ease upside 

 down on the ceiling. 



Senses. Insects have the five senses known 

 to man. It is possible that they have others 

 of which man does not know the nature be- 

 cause he does not possess them himself. Smell 

 seems to be the sense upon which they rely 

 most. In the antennae, or feelers, which are 

 attached to the head, are very small pits, the 

 organs of smell; June beetles have nearly 

 80,000 such pits. With the antennae insects 

 also feel, and in some cases hear. On a 

 locust the organs of hearing, more nearly cor- 

 responding to human ears, are on the sides 

 of the abdomen; on katydids and crickets they 

 are on the forelegs. Insects usually have three 

 simple eyes on the top of the head, and two 

 compound eyes, each made up of from a dozen 

 to 30,000 single eyes. But their sight seems 

 to be very limited. 



When it is remembered that most insects 

 are but a fraction of an inch in length, the 

 exceeding smallness of the organs described 

 above is apparent. 



Food and Location. Most insects feed on 

 vegetable matter, either living or dead, some 

 on decaying flesh, some on the tissues of live 

 animals; others are parasites (which see). 

 They are found anywhere where there is food 

 for them to eat, even in the Arctic regions. 

 Though some live in the water all or part of 

 their lives, there are no insects in the sea. 

 Nearly all perish in winter, only their eggs 

 remaining to perpetuate their species. 



Classification of Insects. Karl von Linne 

 (Linnaeus), in the eighteenth century, arranged 

 insects, according to their wings, in seven 

 classes. Entomologists now distinguish nine- 

 teen classes, but Linne's names are retained for 

 the seven principal ones. It will be noticed 

 that most of the names end in -ptera, the 

 Greek word for wings. 



1. Apt era (wingless) are primitive insects, 

 including the springtails, seen in large numbers 

 on the surface of pools. 



2. Coleoptera (sheath- winged) are the bee- 

 tles. The fore wings are leathery and veinless. 

 The hind wings are broad and membranous and 

 fold up under the fore wings when the beetle 

 is at rest. 



3. Corrodentia (gnawing) include book lice. 



4. Diptera (two-winged) are the true flies: 

 mosquitoes, house flies, horse flies, botflies and 

 others. 



5. Ephemerida (lasting-a-day) are the May 

 flies, familiar to people who live on lakes or 

 rivers. 



6. Euplexoptera (wings well folded) are the 

 earwigs, recognized by forceplike appendages 

 on the tip of the abdomen. 



7. Hemiptera (half-winged) are sucking-bugs, 

 among which are the chinch bugs, scale in- 

 sects, plant lice, "kissing bugs," and the large 

 water bugs that fly about arc lights. Their 

 mouths are specially formed for sucking juice 

 or blood. 



8. Hymenoptera (membrane-winged) em- 

 brace bees, ants, wasps, gall-flies. All the social 

 insects except the termites are included in this 

 division. The habits of an interesting member, 

 the fig-wasp, are described in the article FIG. 



9. Isoptera (equal-winged) are the white ants 

 or termites which in Africa and South America 

 build huge mounds and eat the timbers of 

 houses. 



10. Lepidoptera (scaly-winged) are best 

 known to us as butterflies and moths. The 

 silkworm is a larva of a moth now domesti- 

 cated. This moth and the honeybee are the 

 only domesticated insects. 



