ARTHROPODA 305 



in great numbers; the cotton-boll worm; the canker-worms and fruit-borers. The 

 silk-worm is a very useful member of the order. The clothes-moth lays its eggs 

 in woolens or furs. 



The adults are usually short-lived and some do not eat at all. The majority 

 of them suck nectar from flowers and juices from ripe fruits and other objects by 

 means of special tubular mouth parts which are modified paired appendages. 

 They carry pollen from flower to flower, effecting cross-fertilization, in some 

 instances. The color of the larvae and the adults is very varied and often has close 

 relation to the environment and habits of the animals. We have already noticed 

 in the chapter on adaptations (Chap. VII) how the coloration may be protective. 

 This is the more needed since the group has many enemies, especially in the larval 

 stage. The power of reproduction is great. Several broods per year may be 

 produced. There are more than 50,000 known species of Lepidoptera, about 8,500 

 of which occur in North America, north of Mexico. The species are more num- 

 erous and striking in the tropical regions of South America. 



Fig. 147. 



y 



y 



Fig. 147. Ths Army WoTiji iCirphis unipuncta). After Riley. ^, caterpillar; B, adult moth. 



Questions on the figures. — What are the principal facts concerning the habits 

 and economic importance of the army- worm? Why is it so called? 



Order Coleoptera {shield-wings). — In this group there is a complete meta- 

 morphosis. The mouth parts are suited to biting and chewing. The front wings 

 (elytra) are hardened and serve as covers for the true membranous wings when the 

 latter are not in use. These are the beetles, — falsely called "bugs." Although a 

 well-defined order the beetles manifest a wide range of variation, as will be seen 

 from the fact that there have been described over 18,000 species for this continent 

 north of Mexico. There are said to be more than 1 50,000 known species of beetles. 



Many of the larvae are commonly known as grubs. The feeding habits are 

 almost as diversified as the form. Many are scavengers and lay their eggs in 

 carrion and other decaying matter; others bore into wood and bark, as the long- 

 horned beetles; some frequent grain, nuts, fruits; others are leaf -eaters; a few 

 devour other insects. The Colorado potato-beetle, the weevils, the museum pest, 

 the locust-borer or the hickory-borer will serve to illustrate some of the more hurt- 

 ful representatives of this immense order. 



Some especially interesting forms are the fire-flies, the sacrabseids which include 

 the sacred dung-beetle of Egypt, and the ladybird-beetle. The latter is useful to 

 man owing to the fact that it preys on certain hurtful insects. In California the 

 cottony-cushion scale, which in some way had been imported from Australia, 



