THE TERRAPIN SCALE. 



47 



The Female Upon the Twig: Rate of Growth. 



To determine the relative rate of growth of females after attaching 

 to the twigs Table XXIX was compiled from the data obtained in 

 1913. This shows an increase from attachment on the twigs to the 

 sixty-seventh day of 500 per cent in height and a pronounced increase 

 in length and width. It is evident from this table that nearly all the 

 growth takes place during the first 1 9 days. 



Table XXIX. — Size of twig-attached females of the terrapin scale after the specified days 

 upon the twigs, Mont Alto, Pa., 1913. 



Date. 



Number 

 of speci- 

 mens. 



Period 

 on twig. 



Average 

 length. 



Average 

 width. 



Average 

 height. 



Aug. 1 . . . 

 Aug. 1 ... 

 Aug. 8... 

 Aug. 19.. 

 Aug. 20.. 

 Aug. 23 . . 

 Aug. 26.. 

 Aug. 29.. 

 Sept. 3 . . . 

 Oct. 21... 



10 

 3 

 3 

 10 

 10 

 13 

 4 

 8 

 13 

 16 



Days. 

 0) 



1 



2 

 4 

 5 

 8 

 11 

 14 

 19 

 67 



Mm. 

 1.542 

 1.600 

 1.65 

 1.649 

 1.619 

 1.686 

 1.762 

 1.887 

 1.996 

 2.057 



Mm. 

 1.03 

 1.058 

 1.141 

 1.297 

 1. 226 

 1.177 

 1.25 

 1.331 

 1.592 

 1.680 



Mm. 

 0.125 





.208 









.615 



.625 



1 Just attached. 

 The Female Upon the Twig: Movement After Attaching to the Twigs. 



It is very doubtful whether the females ever reattach after the first 

 week's sojourn upon the twigs. During the first few days specimens 

 have been observed to move, but whether or not the proboscis had 

 been inserted into the host is unknown. Efforts were made to deter- 

 mine this, but no data were obtained. However, observations made 

 upon specimens attached to slowly drying twigs indicate that they do 

 not change position after the eleventh day. 



The Derm. 



With the arching of the dorsum during the first week the flat wax 

 scale which protected the female larva during the migration from 

 leaf to twig scales off; meanwhile the exposed surface thickens and 

 hardens until by the end of the week it is so rigid that it responds to 

 the growth changes by crimping. This hardening and thickening of 

 the dorsum which produces the hard shell-like derm is completed by 

 the twenty-fifth day. The excretion of wax, however, continues 

 and wax flakes can be found attached to the derm up to the time of 

 death. 



HONEYDEW. 



The attachment of the females to the twigs marks the beginning 

 of the maximum period of honeydew deposit. If it were not for the 

 deposit at this time the honeydew would be of very little economic 



