THE DESERT CORN FLEA-BEETLE. 



9 



The incubation period (Table II) varied from 3 days in the month 

 of July and August to 1 5 days during March and April. The average 

 time required for 314 eggs was 5.8 days. The egg stage was secured 

 by placing freshly laid eggs within newly made plaster of Paris cages, 

 the eggs being placed dhectly upon the plaster, which had been pre- 

 viously darkened with waterproof India ink. This plaster not only 

 kept the eggs sufficiently moist, but also kept down any fungous, 

 growth until the eggs could have time to hatch. Just previous to 

 hatching the eggs darken shghtly, taking on a yellowish tinge, and 

 the larvae escape by bursting one side of the eggshell. 



Table II.- 



-Length of egg stage of (he desert corn flea-beetle (Chaetocnema ectypa) at Tcmpe, 

 Ariz., 1913, 1914, 1915. 



Cage No. 



Date 

 laid. 



Num- 

 ber. 



Date 

 hatched. 



Num- 

 ber. 



I-ength 

 of incu- 

 bation 

 period. 



Aver- 

 age 

 mean 

 tem- 

 pera- 

 ture. 



Bi 



1913. 

 Aug. 27 



Aug. 28 



Aug. 29 



Aug. 30 

 Sept. 7 

 Sept. 19 

 Sept. 29 



1914. 

 Feb. 27 



Mar. 18 



Mar. 20 



1915. 

 May 22 

 June 12 



July 13 



July 22 



23 



24 



62 



75 



36 



5 



6 



20 

 30 



15 



25 

 25 



22 



23 



391 



(Aug. 30 



^Aug. 31 



(Sept. 1 



/..do.... 



\Sept. 2 



/..do.... 



\Sept. 3 



Sept. 4 



Sept. 11 



Sept. 22 



Oct. 6 



Mar. 12 

 (Mar. 28 

 hiar. 29 

 (Apr. 1 

 /Apr. 3 

 \Apr. 4 



May 27 

 June 17 

 /July 16 

 IJuly 17 

 July 25 



1 



8 

 14 



5 

 19 

 12 

 40 

 35 

 36 



5 



5 



20 



17 



6 



3 



1 

 7 



25 



25 



6 



16 



8 



Days. 

 3 

 4 

 5 

 4 

 5 

 4 

 5 

 5 

 4 

 3 

 7 



13 

 10 

 11 

 14 



14 

 15 



5 

 5 

 3 

 4 

 3 



°F. 



87 



85 



85 



85 



84.3 



81 



81 



81 



87 



83 



71 



61 



64 



63.5 



62.6 



61 



61 



74.6 



80 



86 



86 



85 



01 



Di 



El 



HI 



Li 



MI 



2 



3 



4 



T 141 



T 163 



T2392 



T360i 



Totals and average 



314 



5.8 









'R. N. Wilson's records. 



' L. J. Hogg's records 



THE LAKVA. 



DURATION' or LARVAL PERIOD. 



It was quit(5 easy to secure the approximate length of the larval 

 stage of many specimens, but owing to the feeding habits, a great 

 deal of difflfuliy was experienced in securing the exact length of this 

 stage. Various types of cages were first tri(>d, all of them embodying 

 the feature that the larvae must be beneath the surface of the ground 

 in order to insure their rcachiiig inaiurity. In the past two years, 

 however, the experiment was m<jdilied \)y placing th(^ n(>wly hatched 

 larvae upon srnail tender sections of com root, witliin the cavity of 

 57154<*— Bull. 4:',(i -17 2 



