CYPRESS BAEK SCALE. 



13 



About 15 minutes after the eggs are deposited, the embryo starts a 

 series of convulsions and after considerable struggling ruptures the 

 membrane inclosing it. The ruptured membrane is pushed down 

 over the abdomen and the larva, which is usually on its back, begins 

 waving its legs about in the air. It usually takes this larva 20 to 30 

 minutes to free itself from the membrane, and after exercising its 

 legs for 30 or 40 minutes it finally gets to its feet and crawls away 

 (PI. TV, E). The larva quite often is stuck to the next expelled egg 

 and may be held out in space for some time, but the struggles of one 

 or the other finally allow the feet of the larva to touch foundation, 

 where it soon makes use of them. 



MIGRATION. 



The larvae become very active soon after exclusion and begin search- 

 ing for a suitable spot upon which to locate. The majority of them 

 immediately work down into the bark crevices or under the cottony 

 secretions of the parent females, where they become attached. Some 

 seem more fastidious than others and travel farther in search of 

 newer feeding grounds. Recently hatched larvae when placed upon 

 favorable young trees do not travel far, and usually settle down after 

 investigating two or three crevices in the bark. 



Larvae placed upon paper were able to travel considerable dis- 

 tances. (See fig. 2.) The average rate of travel for six larvae was 

 54.25 cm. per hour, which they were able to maintain for several 

 hours. The greatest distance traveled by one larva was 174 cm. in 

 two hours. One larva, after traveling 124.46 cm. in four hours, ap- 

 parently put its last efforts into trying to pierce the paper with its 

 proboscis. Table I gives the time, distance, and rate per hour trav- 

 eled by six cypress bark scale larvae on black paper for the first few 

 hours of their migration. Black paper was used in order to facili- 

 tate following the tiny pale larvae in their wanderings. When white 

 paper was used the larvae were soon lost. There seemed to be a slight 

 phototropism in the case of most larvae, the majority of them finally 

 wandering toward the light. 



Table I. — Record 6f travel of six ftrst-instar lariXB of the cypress bark scale on 

 rather smooth black paper. 



No. 



Time. 



Distance. 



Rate per 

 hour. 





Hours. 



Cm. 



Cm. 



1 



1.5 



109. 22 



72.81 



2 



2.5 



143.51 



57.40 



3 



4.0 



• 124. 46 



31.11 



4 



2.0 



173. 99 



86.99 



5 



2.0 



142.24 



71.12 



6 



2.0 



66.04 



33.02 



Average. 



2.333 



126. 577 



54.255 



