INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 93 



of them hatch, and this accounts for the large number necessary to 

 produce so many lice for the coming spring. In the Eastern States 

 where the winters are very severe it is estimated that only one per 

 cent hatch. In California, however, a much larger percentage is able 

 to withstand our milder climate, and so the succeeding infestations 

 are even more severe here than they are in colder climates. 



Just before the apple buds show green the eggs begin to hatch. 

 This, of course, depends entirely upon the weather, and an early 

 spring will bring a much earlier hatch than will a cold, late spring. 



Stem-Mothers.— The young which hatch from the eggs in the early 

 spring give rise to all succeeding generations, and are known as 

 stem-mothers when fully developed. The first born are darker green 

 than any of the succeeding broods. In seeking food they work into 

 the newly opening buds and upon the first tender leaves. Due to 

 their small size they can scarcely be noticed except by very careful 

 observation. In warm weather the young will develop in two or 

 three weeks and become adult stem-mothers. The stem-mothers, 

 which are always wingless, still appear dark green and have dark 

 head, feet, tail and honey tubes. 



Second Generation.— Each stem-mother has the power (which we 

 call parthenogenesis) to give birth to living young without inter- 

 course with a male, for no males appear at all until late in the fall. 

 The young thus born alive constitute the second generation. They 

 are light green in color, are all parthenogenetic viviparous, or agamic 

 females, and though most of them are wingless, a very few winged 

 individuals appear. 



Third Generation.— The new broods of the second generation 

 develop in a few weeks and in turn give birth to living young like 

 themselves, but this generation is accompanied by a large number of 

 winged females. The apterous and winged viviparous females of 

 the succeeding generations are those most usually observed in the 

 orchards and cause the greatest amount of damage. A brief descrip- 

 tion of each is as follows : 



Wingless Viviparous Female. — This form is somewhat larger than 

 the original stem-mother, and is lighter green in color, with a yel- 

 lowish tinge. The cornicles (honey tubes), tail, part of the antennae 

 and the extreme tips of the feet are dark. They also give birth to 

 winged and apterous viviparous females. 



Winged Viviparous Female.— These are recognized at once by their 

 wings, which are usually folded roof-like over the back. The general 

 color is black and green (the head, thorax, cornicles and portions 

 of the legs and antennas being black and the remainder green). Like 

 the apterous forms they have power to produce both winged and 

 wingless viviparous females. A crowded condition or lack of food 

 supply results in the production of a larger percentage of the winged 

 forms. 



The appearance of the winged individual is very significant in that 

 this migratory form is the principal means of distribution and of the 

 formation of new summer colonies. 



Throughout the entire summer months brood upon brood, each in 

 turn producing other broods, give rise to millions of this destructive 



