THE HOKSE-KADISH FLEA-BEETLE. 9 



Table 1. — Egg record of a single female horse-radish flea-beetle. 1 



Date. 



Number 



of eggs 



deposited. 



Remarks. 



May 17 

 27 

 28 



June 3 

 7 

 8 

 14 

 17 

 21 

 22 

 25 

 27 

 29 

 30 



July 1 

 2 

 3 

 12 

 14 

 17 



18 

 22 

 30 



Aug. 3 



7 



22 

 22 

 17 

 23 

 26 

 2 

 4 









Within 48 hours. 







Male added. 



25 



Copulating. 

 Within 48 hours. 



44 

 24 

 44 



Within 48 hours. 

 Copulating. 

 Hatched July 12. 



28 

 21 

 22 

 39 





Within 72 hours. 



Mass; not counted; estimated at 22 



Copulating; eggs laid about July 



hatched. 

 Copulating. 



Copulating; within 36 hours. 

 Within 5 days. 

 Within 72 hours. 

 Female dead; male still alive. 



11 







7 

 26 

 22 





i Within 24 hours in each case, unless otherwise mentioned, eggs were always removed. 



Incubation. — The incubation period of the egg varied from 7 to 14 

 days, as the following data show : 



Table 2. — Incubation period of eggs of horse-radish flea-beetle. 



Number 

 deposited. 



When deposited. 



Date of hatching. 



Incubation period. 



Larvae 

 working. 



20 



May 1 



Before May 17 



May 11 



Bays. 



14 (approximate) 



10 



May 17. 



( ) 



do 



39 .. 



May 11 





14 





28 .. 



July 1 



July 12 



11 





13 



July 10, 11,12.... 

 June 27 



July 17 







July 4 or 5 















The months of May, June, July, and August were from 3.6° to 

 5° F. below normal. 



THE LARVA. 



On hatching the young larva crawls about the leaf for some time. 

 Several individuals, observed over an hour, showed no particular 

 course. Some went up toward the tip, others toward the crown, 

 where they were lost from sight, but none started feeding. A small, 

 tender petiole, recently invested by numerous larvse, showed that 

 they had entered at different places along the inner side. 



As the larvse grow and feed in the tissues of the petioles and mid- 

 ribs of the leaves, their presence is indicated by darkened or dead 

 areas, where they have approached the surface. When the larvae are 



