INSECTS 



of many small eyes, from 50 in some ants to many thou- 

 sands in a butterfly or dragon-fly. Between these com- 

 pound eyes, from one to four simple eyes are to be found 



INSECTS 



807 



1139. Larva of a sphinx moth. 



1138. Nymphs of the four-lined leaf-bug and adult of 



the tarnished plant-bug. 



The smallest one is the nymph recently hatched. The next 

 is the nymph after the first moult. The imago is 

 shown at the right. Hair lines at the right of nymphs, 

 and small figure near imago indicate the natural size. 



in many adult Insects. Caterpillars and other larvae pos- 

 sess only simple eyes. It is thought that each facet of the 

 compound eye sees a part of an object; thus the whole 

 eye would form a mosaic picture on the Insect's brain. 

 The simple eyes doubtless see as our eyes do, and seem 

 to be best adapted for use in dark places and for near 

 vision. Insects do not see the form of objects distinctly, 

 but their eyes are doubtless superior to ours in distin- 

 guishing the smallest 

 movements of an ob- 

 ject. It is now supposed 

 that no Insects can dis- 

 tinctly see objects at a 

 freater distance than 

 feet. It must be a 

 sixth sense, a sense of 

 direction, which en- 

 ables the bee to find its 

 way for a mile or more 

 back to its home. In- 

 sects are doubtless 

 able to distinguish the 

 color of objects, and 

 some Insects seem to prefer certain colors. Blue is said 

 to be the favorite color of the honey-bee, and violet that 

 of ants ; ants are also apparently sensitive to the ultra- 

 violet rays of light, which man cannot perceive. It is 

 generally supposed that the shape and high colors of 

 flowers attract Insects: but recent ex- 

 periments seem to show that Insects 

 are guided to flowers by the sense of 

 smell rather than by sight. 



The hard outer skin of an Insect 

 has no nerves distributed in it, hence 

 it is not sensitive; but it is pierced 

 with holes, in which grow hairs that 

 are in connection with nerves at their 

 base. It is by means of these sensory 

 hairs that Insects feel, and are sensi- 

 tive to touch on most parts of the 

 body. 



Doubtless Insects are 

 not deaf, for we know 

 that many of them make 

 sounds, and it must nat- 

 urally follow that they 

 have ears to hear, for 

 there is every reason to 

 suppose that they make 

 these sounds as love- 

 songs to attract the 

 sexes, as a means of 

 communication, or possi- 

 bly to express their emo- 

 tions. Some think that 



1142. A grub. 

 Larva of a beetle. 



1140. Tent-caterpillar. 



1141. A maggot. 

 Larva of a dipterous insect. 



bees and ants hear sounds too shrill for our ears. In- 

 sects have no true voice, but produce various noises me- 

 chanically, either by rapid movements of their wings, 

 which causes the humming of bees and flies, or by fric- 

 tion between roughened surfaces on the body or its ap- 

 pendages, thus producing the rasping sounds or shrill 

 cries of some crickets and grasshoppers. The house-fly 

 hums on F, thus vibrating its 

 wings 335 times in a second, 

 while the wing tone of the 

 honey-bee is A. Usually the 

 males are the musicians of the 

 Insect world, but it is the fe- 

 male of the familiar mosquito 

 which does the singing, and 

 the "biting" also. The male 

 mosquito doubtless hears the 

 song of his mate by means of 

 his antenna, as the song 

 causes the antennal hairs to 

 vibrate rapidly. Organs which 

 are structurally ear-like have 

 been found in various parts 

 of the body of Insects. The 

 common brown grasshoppers of the fields have a large 

 ear on each side of the first segment of the abdomen; 

 one can easily distinguish with the naked eye the mem- 

 brane or tympanum stretched over a cavity. Many of 

 the long-horned green grasshoppers, katydids and 

 crickets have two similar ears on the tibia of each 

 front leg. Some think that mosquitoes have the faculty 

 of the perception of the direction of sound more highly 

 developed than in any other class of animals. 



Insects undoubtedly possess the sense of taste. When 

 morphine or strychnine was mixed with honey, ants 

 perceived the fraud the moment they began to feed. 

 The substitution of alum for sugar was soon detected 

 by wasps. Bees and wasps seem to have a more delicate 

 gustatory sense than flies. Taste organs have been 

 found in many Insects, and are usually situated 

 either in the mouth or on the organs immediately 

 surrounding it. 



Many experiments have shown that the antenna? 

 are the principal organs of smell in Insects. 

 Blow-flies and cockroaches which have had their 

 antennas removed are not attracted by their fa- 

 vorite food, and male Insects find 

 their mates with difficulty when 

 deprived of their antennae. 



The familiar world which sur- 

 rounds us may be a totally differ- 

 ent place to Insects. To them it- 

 may be full of music 

 which we cannot 

 hear, of color which 

 we cannot see, of sen- 

 sations which we can- 

 not perceive. Do In- 

 sects think or rea- 

 son? Why not? Their 

 actions are said to be 

 the result of inherited 

 habit or instinct. But 

 some of them have 

 been seen to do things 

 which require the ex- 

 ercise of instinctive 

 powers so acute and 

 so closely akin to rea- 

 son that one can 

 hardly escape the 

 conclusion that some 

 Insects are endowed 

 with reasoning 

 powers. 



Their Number, Size and Age. -Experts guess that 

 there are from 2,000,000 to 10,000,000 different kinds 

 of Insects in the world. Only about 400,000 of these 

 have yet been described and named by man. Between 

 30,000 and 40,000 are now known in North America. 

 Four-fifths of all the kinds of animals are Insects; some 

 single families of Insects are said to contain more spe- 

 cies than one can see stars in a clear sky at night; and 



1143. Cocoon of pro- 



methea moth. 

 Made in the roll of a leaf. 

 The insect weaves a weh 

 about the leaf- stalk and 

 ties it to the parent 

 stem, so that the leaf 

 cannot fall. 



