THE DESEET COEISr FLEA-BEETLE. 



13 



THE ADULT. 



The change from pupa to adult takes place rather quickly, but 

 often a day or two passes before the adult entirely assumes the char- 

 acteristic shining black. When the adults first emerge from the 

 pupal state they are almost white, but after a short time gradually 

 become darker, begitinmg with the legs, then the elytra, and finally 

 the whole body is enveloped. 



The adults are very soon able to jump nimbly and it is this habit 

 which has given this group their name of '^flea-beetles." They are 

 quite easily alarmed, leap quickly from a plant, and, fallmg to the 

 ground, often feign death in order to escape their enemies. 



To the ordinary observer the males and females are very much 

 ahke, the difference bemg largely one of size, the male averaging 

 slightly smaller than the female. A gravid female can be distin- 

 guished by the size of her abdomen, but large males are often larger 

 than small females, so that the distinction is not very reliable. 



ADULT DEVELOPMENT. 



After the adults emerge several days must elapse before their 

 sexual development is completed. Numerous records on this point 

 were made by the writer as well as by J. H. Newton, assistant in the 

 bureau at Tempe, and it was found that copulation usually takes 

 place from 4 to 6 days after emergence and oviposition from 4 to 5 

 days thereafter. Table V show^ the length of the period elapsing 

 from issuance to oviposition as observed in five females. This varied 

 from 7 to 14 days, the average being 9.8 days. 



Table V 



-Length of life of Uic desert corn flea-beetle (ChaetocneTna ectypa) at Tempe, 

 Ariz., 1915. 



TJate adult issued. 



, Age at 

 Date OA-i- liegin- 

 position niiig of 

 began, j ovipo- 

 sition. 



Adult 

 died. 



Length 

 of life. 



On or Ijefore Apr. 2.5. 

 On or before Apr. 20. 



MayVrrj) 



May 17 



I>o 



July li; 



\)o 



On or before Apr. 28. 



Apr. 29 



Apr. 28 



May 22 



May 2« 



May 29 



.Tuly 23 



,Tuly 25 



May 7 



Days. 



A verage. 



June 1 

 May 31 

 May 27 

 June 15 

 ..do.... 

 July 31 

 ..do.... 

 July 20 



Days. 

 38+ 

 41 + 

 20 

 29 

 29 

 15 

 15 

 83 



33. « 



.NU.MHKIt OK ECiCH DKI'fjHITKI) HY ONE KEMALE. 



TIk! females usually lay their eggs in stages, tiuire l)eing from one 

 to two, hikI soiiu'tiriics tlinu", difTcxcnt egg-laying singes, often extonrl- 

 ing over half u month. As shown in Tiihlc^ VI, a IViuale may deposit 



