ii2 REPORT OF NEW JERSEY STATE MUSEUM. 



eggs, from which in spring hatch wingless forms which, in a few days, 

 give birth to living young resembling the parents, and, like them, vivip- 

 arous, i. e., giving birth to live young, and parthenogenetic, i. e., neither 

 male nor female. These young are in turn ready to reproduce in a few 

 days, and give birth to anywhere from 4 to 8 daily, according to condi- 

 tions. Some time during the early summer winged individuals are pro- 

 duced and these fly to other localities or other food-plants, thus spread- 

 ing the species. They also are parthenogenetic and usually viviparous, 

 and found colonies wherever they alight, the progeny being winged or 

 wingless or some of each sort. In the fall, when sap ceases to run and 

 food becomes scarce, sexed individuals, male and female, are produced, 

 and these copulate, the female laying the winter eggs. There are numer- 

 ous modifications of this life history; but in a general way it applies to a 

 large percentage of the species. 



Some species have alternate food-plants; i. e., they feed upon one plant 

 late in fall and early spring, using it to winter upon, while in summer 

 they fly to some annual like the melon or hop that dies down completely 

 in fall and renders migration to the winter plants necessary again in late 

 summer or fall. The spring migrations usually occur in June and the air 

 is then sometimes apparently alive with these minute flying lice. 



The rate of increase among these insects is such that, were it not for 

 the numerous natural checks, they would soon destroy every particle of 

 plant life which they are able to feed upon. 



Remedial measures are, winter pruning where eggs are noticed in large 

 numbers, the cuttings to be burnt; application of contact insecticides 

 early in the season to destroy the stem-mothers ; application of contact 

 insecticides at any time when the insects are noticed, keeping in mind at 

 all times that it is easier to kill a few than to reach a great many, espe- 

 cially if they feed so as to distort the leaves or curl them up into shelters 

 not easily penetrated by insecticides. Indoors the pyrethrum, dry or in 

 the form of decoction, is a favorite and effective remedy. In the field, 

 garden or greehouse, tobacco decoction, whale-oil soap or kerosene emul- 

 sions are used. Soluble or miscible oils are not safe for summer use at 

 effective strengths. Whale-oil soaps are used at from 1 pound to 4 to 6 

 gallons of water, according to the species to be reached. Kerosene emul- 

 sion is used diluted with from 10 to 15 times its bulk of water, the green 

 lice being most easily destroyed in all cases and the black lice the most 

 resistant. 



Tobacco decoctions, home-made and commercial, are also used, and 

 some of the commercial preparations are more effective than the home- 

 made mixtures. 



Whatever mixtures are used thoroughness in application is always 

 essential. All these mentioned are contact poisons and of no effect unless 

 actually brought into direct touch with the specimens. Therefore it re- 

 quires not only a proper nozzle to make a fine spray, but also a sufficient 

 amount of force to drive this spray to the specimens. 



Under some circumstances even cold water will kill plant lice, and a 

 cold storm in middle or late June will play havoc with the migrating 



