132 INSECTS OF ECONOIMIC IMPORTANCE 



in color with a narrow, dark-green stripe down the 

 back and about J4 of an inch long when mature; 

 they tie the leaves together and feed on them, dis- 

 figuring the plants; the caterpillar becomes grown 

 in from 15 to 20 days and pupates between two 

 leaves or in a folded leaf; in about one week the 

 moth appears ; in greenhouses it breeds all the year 

 and attacks chrysanthemums, geranium, cinerarias, 

 sweet peas and other plants. 



Control — Spray wnth arsenate of lead, 2]/^ 

 pounds to 50 gallons of water, as soon as the cater- 

 pillars appear and hit the undersides of the leaves ; 

 hand-pick the caterpillars. 



The greenhouse w^hite-fly "^ (Trialciirodcs 



vaporarioriim) 



Order — Hemiptera 



The adult insect has four pure white wangs and 

 is about 1-16 of an inch in length; the young insects 

 are oval, flat, and whitish and cling closely to the 

 undersides of the leaves where they suck out the 

 juices. 



The small greenish eggs attached to the under- 

 sides of the leaves hatch in about eleven days and 

 the young insects attain their growth in from 3 to 4 

 weeks ; there are several generations each year, and 

 the injury often becomes very severe. 



Control — An all-night fumigation with hydro- 

 cyanic acid gas, i ounce of cyanide to 3500 cubic 

 feet 'of space, has given good results; it is neces- 

 sary to fumigate at intervals of ten days to two 

 weeks. Spraying with soap, i pound in 6 gallons 

 of w^atei; is of advantage, but if the solution is ap- 

 plied frequently the soap should be washed from 

 the plants occasionally by spraying with clear 

 water. 



