6 BULLETIN 1040, V. S. DEPARTMENT OF AGRICULTURE, 



SEASONAL HISTORY. 



A most important feature in the biology of this insect was deter- 

 mined by observing the habits of the insect during the spring migra- 

 tion. The females, which during the winter have developed almost 

 to maturity on the twigs, foliage, and fruit, migrate, in the spring, 

 down the limbs to the trunk to oviposit. This migration usually 

 begins during the early part of April and continues throughout the 

 month of May. It is estimated that over 90 per cent of the insects 

 take part in this movement, although not all have reached full de- 

 velopment at this time. They settle on the rough places in the bark 

 of the main limbs and trunk and soon begin ovipositing. On severely 

 infested trees these accumulations of females with their cottony egg 

 masses appear as large bunches of cotton hanging from the limbs 

 and massed about the trunk and may be collected by handfuls. 

 (Fig. 4.) These egg masses begin to hatch the latter part of May or 

 early part of June, and the young larvae start a migration back up 

 the main limbs to the foliage and green fruit. The young settle 

 along the midribs of young foliage, on the tenderest twigs, and under 

 the sepals of the green fruit. Here they start feeding and their de- 

 velopment is comparatively slow. By late fall many have become 

 half grown and have settled in the more secure positions on the 

 bud end or navel end of the fruit or between the fruit in clusters, and 

 their development from then on is very irregular. During the 

 winter many may have reached the oviposition stage, but the major- 

 ity of the insects are still immature. There is a great reduction of 

 numbers throughout the late fall and winter ; in fact, on many trees 

 it is often difficult to find them, but with the opening of spring the 

 matured forms again enter into the migration. There is only one 

 main generation a year, although the retarded development of some 

 insects and the hastened development of others cause an overlapping 

 of generations and consequently the presence of some insects in 

 various stages of development at different times of the year. There 

 is a possibility of an offhatch or overlapping of generations in the 

 appearance of egg masses during the winter. This occurrence, how- 

 ever, is of minor importance in that the numbers of the mealybug are 

 at their lowest at this time and most of the damage to the host has 

 already occurred. 



The young larvae hatching from the egg masses in June are often 

 liilled by hot weather. In the summer of 1917 a very large percent- 

 age of the larvae and eggs were destroj^ed by a short period of hot 

 weather when the temperature exceeded 110° F. Again in the sum- 

 mer of 1918 the hatching occurred just before a warm spell and many 

 larvae were killed. That weather conditions and natural enemies 

 are powerful factors in the control of this mealybug is very evident, 



