172 Bugs, Cicadas, Aphids, and Scale-insects 



plump-bodied, pale-green insects, some with two pairs of long, delicate, 

 transparent wings, some without wings, common on llowcrs in conserva- 

 tories and gardens and known as "green fly." Other often-noticed kinds 

 are the cockscomb gall-louse of the elm and the "blights" of various foliage 



trees, as alder-blight, beech-blight, elm- 

 blight, etc., these "blight" aphids all 

 secreting conspicuous white woolly masses 

 of wax and most of them also excreting 

 honey-dew, which is conspicuous on the 

 leaves and on the sidewalks under the 

 trees. 



Of more economic importance are 

 some of those plant-lice which infest 

 crop-plants, the extraordinarily ruinous 

 grape-phyllo.xera, for example, the apple- 

 ap])le-a])his, the cherry-, plum-, and 



Fig. 244. — The soullurn grain plant- 

 louse, Toxoptera grumineum, winged 

 migrant. (.\fter Pergande; much 

 enlarged.) 



tree root-louse, and the woolly 

 peach-aphids, the corn-root louse, the hop-louse, and the cabbage-aphis, 

 turnip-louse, and other aphid pests of garden vegetables. All of these 

 insects are minute soft-bodied defenceless creatures, which effect their great 

 injuries to their host-plants by virtue 

 of great numbers. Fitch, New York's 

 first state entomologist, estimated the 

 number of cherry-aphids that were 

 living at one time on a small \'oung 

 cherry-tree to be 12,000,000. Although 

 uncounted millions of the toothsome 

 juicy little aphid bodies are being con- 

 stantly eaten in spring and summer by 

 eager predaceous insects, such as lady- 

 bird beetles, certain syrphid-fly larva; 

 and aphis-lions (larvae of lace- wing and hemerobius flies), just as constantly 

 are new millions being produced by the fecund aphis mothers, most of the 

 young being born alive and requiring but a few days to complete their 

 growth and development, and to be ready to take up the ])roduction of 

 young themselves. 



Professor Forbes has made an estimate of the rate of increase of the corn- 

 root louse that shov^-s this great fecundity. A single stem-mother of the 

 corn-root aphis produces twelve to fifteen young that mature in a fortnight. 

 "Supposing that all the plant-lice descending from a single female hatched 

 from the egg in spring were to live and reproduce throughout the year, we 

 should have coming from the egg the following spring nine and a half tril- 

 lion young. As each plant-louse measures about 1.4 mm. in length and .93 



Fig. 245. — The southern grain-louse, 

 Toxoptera gramineiim, wingless. A, 

 female; B, young nymph; C, older 

 nymph. (.After Pergande; much en- 

 larged.) 



