808 



INSECTS 



there are as many butterflies as birds in North America. 

 The larger part of the land animals are Insects, and it 

 is asserted that the larger proportion of the animal mat- 

 ter existing on the lands of the globe is 

 probably locked up in the forms of In- 

 sects. 



Insects vary in size from little beetles, 

 of which it would take 100, placed end to 

 end, to measure an inch, up to tropical 

 species 6 or 8 inches in length, or of equal 

 bulk to a mouse. 



Insects have a very long, but, as yet, 

 very imperfect pedigree extending through 

 the geological ages to Silurian times. Fos- 

 sil remains of many different kinds of In- 

 sects have been found in the rocks (Fig. 

 1136) ; even such delicate Insects as plant- 

 lice left their impress on the rocks ages 

 ago. In the car- 

 boniferous or coal 

 age, the Insect 

 world was evi- 

 dently quite dif- Lengthwise 

 f erent from that section of the 

 of to-day, f or f os- P r o m e t h e a 

 sils of veritable cocoon ' 

 Insect mammoths Showing at the 

 have been found; apexthevalve- 



1144. 



like opening 

 through which 

 the moth 

 escaped. 



1145. End of cocoon of 



Cecropia moth. 

 Inside view, showing 

 where the moth gets out. 



dragon-flies with 

 a wing-expanse of 

 from 2 to 3 feet 

 then existed. In- 

 sect fossils found in the Ter- 

 tiary rocks indicate that there 

 were more kinds of Insects then 

 than now. 



Their Growth and Transfor- 

 mations. Fig. 1137. Insects 

 begin life as an egg ; in some cases the egg stage 

 is passed within the body of the mother, which then 

 gives birth to living young. The eggs of Insects ex- 

 hibit a wonderful variety of forms, sizes, colors and 

 characteristic markings. A single scale Insect may lay 

 thousands of eggs, while some plant-lice produce only 

 one. Remarkable instinct is often shown by the mother 

 Insect in placing her eggs where her young will find 

 proper food. 



From their birth the young of some of the lowest or 

 most generalized Insects closely resemble their parents, 

 and they undergo no striking change during their life; 

 hence are said to have no metamorphosis. 



In the case of grasshoppers, stink-bugs, dragon-flies, 

 and many other Insects, the young at birth resemble 

 their parents, but have no wings. As they grow, wings 

 gradually develop and often changes in markings occur, 

 until the adult stage is reached. The growth, however, 

 is gradual, and no striking or complete change occurs, 

 and these Insects are said to undergo an 

 incomplete metamorphosis. The young 

 Insects in all stages are called nymphs 

 (Pig. 1138); thus Insects with an incom- 



1146. Pupa of 

 tomato worm. 



1147. The cabbage butterfly. 



plete metamorphosis pass through three different forms 

 during their life: an egg, the young or mtmph stage 

 and the adult. 

 From the eggs of butterflies, moths, flies, beetles, 



1148. Imago of a tent-caterpillar. 



INSECTS 



bees and some other Insects, there hatches a worm-like 

 creature, much unlike the parent Insect. It is called a 

 larva (Fig. 1139); the larvae of butterflies and moths 

 are often called caterpillars (Fig. 1140); maggots are 

 the larvae of flies (Fig. 1141) ; and the term grub is 

 applied to the larvae of beetles and bees (Fig. 1142). 

 When these larvae get their full growth, some of them go 

 into the ground, where they form an earthen cell, while 

 others proceed to spin around themselves a silken home 

 or cocoon (Figs. 1143, 1144, 1145). In these retreats the 

 larvae change to a quiescent or lifeless-appearing crea- 

 ture which has little resemblance to either the larva 

 or the parent Insect. It is called a pupa (Fig. 1146). 

 The pupae of butterflies are often called chrysalids. 

 Flies change to 

 pupae in the 

 hardened skin 

 of the maggot. 

 Some pupas,like 

 those of mos- 

 quitoes, are 

 very active. 

 Wonderful 

 changes take 

 place within the 

 skin of the pu- 

 pa. Nearly all 

 the larval tis- 

 sues break down and the Insect is practically made over, 

 from a crawling larva to a beautiful, flying adult Insect. 

 When the adult is fully formed, it breaks its pupal 

 shroud and emerges to spend a comparatively brief ex- 

 istence as a winged creature. Such Insects are said to 

 undergo a complete metamorphosis, and pass through 

 four strikingly different stages during their life: the 

 egg, the worm-like larva, the quiescent pupa, and the 

 adult Insect. Such remarkable changes or transforma- 

 tions make the story of an Insect's life one of intense 

 interest to one who reads it from nature's book. Vari- 

 ous kinds of adult Insects, or imagoes, are shown in 

 Figs. 1147-1152. 



No two kinds of Insects have the same life-story to 

 tell. Some pass their whole 'life 

 on a single host; some partake 

 of only a certain kind of food, 

 while others thrive on many 

 kinds of plants ; some are can- 

 nibals at times, and others, like 

 the parasites, are boarders with- 

 in their host, while many prey 

 openly on their brethren in the 

 Insect world. Usually the life 

 of the adult Ins'ect is brief, but 

 ants have been kept for thir- 

 1149. A beetle. teen years, and the periodical 



The adult of a borer larva, cicada has to spend seventeen 

 years as a nymph underground 



before it is fitted to become a denizen of the air. The 

 winter months may be passed in any of the different 

 stages of the Insect's life. Two very closely allied In 

 sects may have very different life habits. 



How They Grow. Many people believe that the small 

 house-flies grow to be the large ones. While most In 

 sects feed after they become adults, they get little or 

 none of their growth during their adult life. Insects 

 grow mostly while they are larvae, or nymphs. The 

 maggots from which the little house-flies develop doubt- 

 less do not have as luxuriant or favorable feeding 

 grounds as do those of the larger flies. In 30 days 

 some leaf-feeding caterpillars will increase in size 

 10,000 times ; and a certain flesh- 

 feeding maggot will in 24 hours 

 consume two hundred times its own 

 weight, which would be paralleled 

 in the human race if a one-day-old 

 baby ate 1,500 pounds the first day 

 of its existence! The skin of In- 

 sects is so hard and inelastic that 

 it cannot stretch to accommodate 

 such rapid growth. But nature ob- 

 viates this difficulty by teaching these creatures how 

 to grow a new suit of clothes or a new skin under- 

 neath the old one, and then to shed or moult the lat 



1150. One of the 



weevil beetles 



With a long and 



strong proboscis. 



