2 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 47 



insect eggs cause little or no damage, but many of the animals 

 that hatch from the eggs are destructive. 



Insects develop by metamorphosis, or change. The young 

 of some kinds, boxelder bugs for example, look like the adults 

 and reach maturity through a series of molts. The young of 

 kinds that look unlike the adults are called larvae, grubs, cater- 

 pillars, or worms. Eggs deposited by moths and butterflies pro- 

 duce caterpillars that feed ravenously and molt several times 

 before they reach maturity. The caterpillars change to pupae 

 (latent stage) for transformation to moths or butterflies. The 

 growth pattern of beetles is similar to that of moths and butter- 

 flies. The young of beetles are often called grubs. 



The following paragraphs contain information about sev- 

 eral kinds of insects and the ways in which they feed. 



Aphids or Plant Lice. — There is a species of aphid for al- 

 most every species of plant. Aphids are sucking insects, fragile 

 and awkward in appearance. They are most commonly green, 

 pink, or black in color. Each aphid, only one-sixteenth to one- 

 eighth inch long, is well equipped with a stout beak through 

 which it draws great quantities of plant juice as it feeds from 

 place to place on tender plant tissue. Heavy infestations of 

 aphids usually produce a noticeable amount of honeydew, on 

 which a sooty mold may grow. Aphids have an enormous repro- 

 ductive capacity. Fortunately they have many natural enemies. 

 Lady beetles, both larvae and adults, fatten themselves on 

 aphids, and the larvae of tiny parasitic wasps feed within them. 



Scale Insects. — Scale insects, small and inconspicuous, are 

 likely to be overlooked until the branches of infested trees or 

 shrubs are encrusted with them. They are sucking insects that 

 live most of their lives under protective shells or scales. They 

 may kill branches, limbs, and whole trees. Each insect is a mere 

 sack of protoplasm with a threadlike beak thrust into the tissue 

 of the plant it feeds upon. The female in most species of scale 

 insects deposits eggs under her shell. The eggs produce crawlers 

 that move away from the shell to find suitable feeding places. 

 When the crawlers settle and begin to feed, each makes a shell 

 for its own protection. 



Borers. — Most borers that attack trees or shrubs are the 

 larvae of beetles or moths. They hatch from eggs deposited on 

 the bark of a tree or shrub. Soon after hatching, they bore into 

 the wood of the plant. Healthy, vigorous trees are unattractive 



