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- 



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, Init, 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 

 a world was evi- 



dently quite dif- L 

 f(n*ent from that 

 Mf to-dav, for fos- 



lii-i-rr ni;Miiiriiitli-; Showing at the 

 ii'i\"u ix-.n Iniii il- apexthevalve- 

 ,' 'J,-' "„,'',.' like opening 



aiap,un-iiiu>. witn throughwhich 

 a wing-expanse of the moth 

 from 2 to 3 feet escaped, 

 then existed. In- 

 sect fossils found in the Ter- 

 tiary rocks indicate that there 

 were more kinds of Insects then 

 than now. 



Thnr 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 lav 

 thousands of eggs, while some plant-lice produce only 

 one. Remarkable instinct is often shown bv the motlier 

 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 I,.,. , , ,, nuiiorphosis. 



In the case of i-i . , i ; -rink-bugs, dragon-flies, 



and many oth. i i , li ,„ing at birth resemble 



their parents. I.nr i, n, ,,,, ^ in-s. As they grow, wings 

 gradually develu|) au-l mIu-h i.-tmiiges in markings occxir, 

 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 

 .^Q/i (Fig. 1138); thus Insects with an incom- 



; moth gets out. 



1147. The cabbaee butterfly. 



plete metamorphosis pass through three different forms 

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

 and the aditlt. 

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



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 larva" of flies (Fig. 1141); and the term gnib is 

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

 When these larvie 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 pnpa (Fig. 1146) 

 The pupffi of butterflies are often called chrysalids 

 Flies change to 



pupa 



the 



1148. Imago of 



caterpillar 



hardened skin 

 of the maggot. 

 Some pupae, like 

 those of mos- 



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 practitall> 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 

 I 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 Insect 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 nvmph 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 Grotc. — 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 

 (Tinsunie two hundred times its own ^^ 

 weiL'ht, which would be paralleled **' " 

 in tlif liunian race if a one-day-old 

 lialiy ate 1,500 pounds the first day 1150. One of the 

 of its existence! The skin of In- weevil beetles 

 sects is so hard and inelastic that With a long and 

 it cannot stretch to accommodate strong proboscis, 

 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- 



^^^ 



