484 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



due to the insects' feeding. Spraying with contact insecti- 

 cides has been suggested, but as the insects feed on the under- 

 side of the leaves it is difficult to reach them. 



Web -worms. There are three or more species of web-worms 

 (caterpillars) that attack, and sometimes defoliate beets and 

 other garden plants. They are called web-worms on account 

 of their habit of spinning fine webs as they feed. The invaded 

 plants may be killed outright, or only retarded in their develop- 

 ment. The slender, greenish worms are marked with many 

 small black spots and sometimes with lighter markings. When 

 fully developed they enter the ground and spin long slender 

 cocoons in which they pupate. The adult moths are greenish 

 or brownish and have a wing expanse of about an inch. 



They may be controlled by spraying with Paris green or 

 arsenate of lead. If the field is plowed late in the fall many of 

 the pupae will be destroyed. As these worms feed on other 

 plants, including many of the common weeds, it is evident 

 that these should be kept out of the garden or fields. 



The Beet Aphis (Pemphigus beta). Sometimes the beets 

 in certain parts of the field are found to be much smaller than 

 the average, and soft and spongy rather than firm as they should 

 be. If such beets are taken from the ground they may be 

 found to be covered with a mold-like substance which is really 

 the flocculent excretion from many little plant-lice that are 

 feeding there. As long as this insect fed on yarrow, door-mat 

 weed, grasses, and other wild plants as it used to, it was, of 

 course, of no economic importance, but as soon as beets began 

 to be cultivated in the region where it occurred it found them 

 more to its liking, and now in some regions many tons of beets 

 are destroyed by it each year. 



If this pest becomes abundant in a field it should be 

 starved out by refraining from planting beets or other root 

 crops there for two or three years. 



OTHER GARDEN INSECTS 



Cut-worms and Army-worms. Most of the common dull 

 grayish cut- worms (caterpillars of certain owlet-moths), hide 



