THE CAMPHOR THRIPS. 11 



HATCHING. 



Hatching has been observed to take place at various times during 

 the day, but in the breeding jars the majority of the thrips seem to 

 hatch during the morning. When ready to hatch, a lidlike cap splits 

 off at the anterior end of the egg, although it remains attached at one 

 side. Sometimes also the egg splits longitudinally, enabling the 

 young thrips to crawl out more easily. It emerges head first and 

 gradually works its way out until it is able to place the front feet on 

 the twig. It then easily draws itself out of the eggshell. When free 

 the thrips at once crawls away in search of food and pays no attention 

 to the empty shell. The entire process of hatching required about 2 

 minutes in the case of several individuals observed. The empty egg- 

 shell does not collapse, but remains intact on the twig, often for a 

 period of several months. 



FIRST-STAGE LARVA. 



The young thrips begin their search for food as soon as they leave 

 the eggs and remain active throughout their larval period. They are 

 found in cracks and lesions of the bark and on the buds and new ter- 

 minal growth. The molt takes place almost anywhere on the limbs 

 or leaves. When ready to molt the larva becomes quiescent for a 

 short time, after which the skin splits along the dorsum and the larva 

 easily liberates itself from the old skin. 



The first instar in summer lasted from 3 to 7 days in the case of 66 

 individuals, with an average of 4.05 days. In winter a longer period 

 is required, running from' 5 to 10 days, with an average of 7.9 

 days. Table 2 gives detailed records for the breeding work, the data 

 for summer and winter being shown separately. 



SECOND-STAGE LARVA. 



Following the first molt the larvae increase in size rapidly and are more 

 conspicuous on the trees, owing to the prominent orange-red coloring. 

 The larvae in this stage are also more active and move about rath er 

 rapidly, covering considerable areas of the host plant. When disturbed 

 they quickly crawl around the limb, seeking a bark lesion for safety, 

 or will go down the limb into the interior of the tree. The favorite 

 feeding place seems to be on the buds and new terminal shoots, when 

 there is any new growth on the trees. On cloudy or rainy days, how- 

 ever, or during a period of cold weather the thrips are seldom seen on 

 the leaves and shoots, but remain down in the bark lesions, where they 

 feed on the cambium layer of the wood. Instances have been noted 

 in which they have tunneled back for several inches under the bark or 

 in the center of the limb. When ready to molt again, the larvae go 

 down under the loose bark or into some crack or lesion, where they 

 pass a brief period of inactivity before shedding the larval skin. 



The second stage lasts only slightly longer than the first, but show 

 a greater individual variation. As shown in Table 2, it ranged from 3 

 to 11 days in summer, with an average of 4.55 days for 59 individuals, 

 and in winter from 6 to 11 days, with an average of 7.94 days. 



PREPUPA. 



The prepupal stage is passed largely in some lesion under the bark 

 and is of short duration. Although the insects in this stage are able 

 to crawl, they show little activity and probably feed very little. 



