Puant Lice InJuRING FOLIAGE AND FRUIT OF THE APPLE 691 
buds show green, and continue hatching for a period of two or three 
weeks depending on weather conditions. Brittain (1915a) reports the 
remarkable observation that on different varieties of apples the eggs 
hatch at the time when the buds on such varieties are showing green. If 
such an observation should prove correct for other sections of the 
country, it would certainly be rather remarkable, to say the least. 
Failure of the eggs to hatch 
That many, in fact a very large proportion, of the eggs do not hatch, 
has been observed by many workers. Tho hundreds and thousands 
of eggs may be found on individual trees, it often happens that only 
comparatively few of these hatch; so that predictions as to outbreaks 
of plant lice cannot be made from any examination during the dormant 
season. Various reasons have been assigned for this failure of eggs to 
hatch, but none of the factors involved have been given sufficient study, 
particularly under experimental conditions. Unfortunately the writer 
has not been able, thru lack of equipment, to do more than make field 
observations, record the percentages of eggs that hatched, and in general 
correlate observed phenomena, in so far as possible, with any or all of the 
factors involved. | . 
The following factors have generally been assigned as contributing to 
the failure of eggs to hatch: 
1. Climatological conditions. These may be (1) temperature — either 
low temperature or sudden changes during the winter or during the 
hatching period; or (2) moisture —cold rains just at or just before 
hatching time, causing the death of the young lice before leaving the eggs. 
2. Various predacious insects and birds, which may destroy or. injure 
large numbers of the eggs during late fall, winter, and early spring. 
3. Non-fertilization of the eggs. This factor, not yet mentioned by 
any worker, may account for the failure of many eggs to hatch. All 
observers agree that the males are very few, constituting a very small 
proportion of the total number of insects. In cage studies many females 
were observed to deposit eggs, thousands in fact, and tho these eggs were 
given the best of conditions the majority failed to hatch. It was 
observed also that many females deposited eggs before mating, and in 
a very short time shrunken eggs were noted on the twigs. Whether non- 
