THE TERRAPIN SCALE. 



23 



£MD 



cates that orchard workers during the migrating period might unwit- 

 tingly aid in the dispersal of this pest. 



It is possible for larvae of the first instar which have attached 

 themselves to leaves to be transferred to other trees, as the following 

 experiment shows. Thirty larvae that had loosened themselves 

 from a wilting leaf were placed on the foliage of another tree July 

 22 at 2 p. m. The first 

 of these was found at- 

 tached July 23 at 8 a.m., 

 and all of them were at- 

 tached by July 24 at 8 

 a. m. 



Dispersal may occur at 

 this period in at least 

 four ways : 



(1) By dropping of lar- 

 vae from dead branches, 

 fruit, etc. 



(2) By wind transpor- 

 tation. 



(3) Through transpor- 

 tation by storm water. 



(4) By animate agents 

 (insects, birds, orchard 

 workers, etc.). 



Mortality During Migra- 

 tion. 



Practically all of the 

 emerged young make a 

 successful migration. 

 The only exceptions are 

 in cases where the larvae 

 stray upon dead branches 

 or the fruit and are unable 

 to return and in the case 

 of those destroyed by the occasional attacks of predatory enemies. 

 The mortality at this time is indicated by the small number of larvae 

 that fail to attach themselves to the leaves. Of the 12,336 larvae 

 that migrated in 1913 from the isolated scales, all but 15 successfully 

 attached to the underside of leaves. The mortality upon the average 

 orchard tree is slightly higher than is shown in the case of these 

 isolated larvae. 



START 



Fig. 7.— Tracings of a young terrapin scale for the first 3 hours 

 and 20 minutes of the leafward migration. Reduced 8 times. 

 Temperature, 86.90° F. (Original.) 



