New York AciticuLTURAL Expeeiment Station. 473 



in an incredibly sboit tinrie, ^ving birth, in turn, to female 

 young at an equally rapid rate with their parents. Winged 

 females are produced from time to time, ajji^arently as occasion 

 demands, for the dissemination of the species. These winged 

 lice fly to other food plants or to other leaves on the same plant 

 and start new colonies. This is continued dur-ing the summer. 

 Jn many cases the lice migrate to new food plants for a portion 

 of the summer. In the fall they may return to food plants of 

 the same species as the original. These migratory broods con- 

 sist of winged females. A generation of sexual forms, true 

 males and females, is produced sometime during the fall. After 

 j>airing. each female produces one or more eggs. The eggs are 

 usually placed on the twigs near the buds. They remain dor- 

 mant all winter, hatching early in the spring into agamic females 

 which, as they start the first broods of the season, are known as 

 •' stem mothers." It will be noticed that no male insects are 

 produced throughout the season until fall. Reproduction is by 

 a process knov,n as budding. The following forms enter into 

 the life cycle of a species during the season. The wingless and 

 winged agamic female, the sexual female, the male, the winter 

 f^gg and the " stem mother." 



The Peincipal Insecticides Used in Combating Plant-lice. 



These kill by contact. Internal jjoisons, such as Paris green 

 and London purple, will not kill plant-lice when sprayed upon 

 the leaves. The reason for this will be ai>parent when it is 

 remembered that these insects suck the sap from beneath the 

 surface of the leaf instead of devouring the leaf itself. The in- 

 secticides used for this purpose include kerosene emulsion, the 

 kerosene- water mixture, whale-oil soap, tobacco in various forms, 

 pyrethrum powder and hot water. 



Kerosene emulaum. — This insecticide may be made after the 

 following formula: 



^Vat(•r 1 gallon. 



Soap, whale-oil soap preferred 14 pound. 



Kerosene oil 2 gallons. 



