12 



BULLETIN 436, U. S. DEPARTMENT OF AGRICULTUEE. 



was ascertained by taking larvae that had already constructed their 

 pupal cells, placing them in a vial, and allowing them to go through 

 these various changes in plain sight. 



Table IV. 



-Duration of j)i'e pupal and pupal stages of the desert corn flea-beetle (Chaetoc- 

 nema ectypa) at Tempe, Ariz., 1915. 



Pupa No. 



Date 

 prepupa 

 formed 



Date 

 of pupa- 

 tion. 



Length 

 of pre- 

 pupal 



stage. 



Date 

 adult 

 issued. 



Length 



of 

 pupal 



stage. 



Aver- 

 age 

 mean 

 tem- 

 pera- 

 ture. 



1 



2 



3 



4 



5 



6 



7 



s 



Apr. 30 

 ...do 



May 8 



May 10 



...do 



...do 



Apr. 27 

 ...do 



May 6 



...do 



May 10 

 May 12 



...do 



...do:.... 

 Apr. 29 

 May 5 

 May 7 

 do 



Days. 

 6 

 6 

 2 

 2 

 2 

 2 



I 



May 13 



...do 



May 14 

 May 17 



...do 



...do 



May 11 



May 13 



do 



Days. 

 7 

 7 

 4 

 5 

 •5 

 5 

 12 

 8 

 6 

 6 

 6 

 6 

 6 

 4 

 S 

 6 

 6 

 3 

 3 

 51 



° F. 

 70 

 70 

 76 

 75 

 75 

 75 

 68 

 70 

 70 

 70 

 73 

 73 

 73 

 76 

 75 

 75 

 75 

 86 

 86 



9. .. 





10 







do 



11 





May 8 



...do 



do 





May 14 



...do 



.do 



12 



13... 





14 





May 10 

 May 10(5) 

 May 11 

 .do 





.do 



15 







Mayl6(5) 

 May 17 

 .do 



16 





17 





18 



19 



Avera 



July 15 



...do 



ge of 23 pu 



July 17 



...do 



pa 



2 

 2 

 31 



July 20 

 ...do 







The duration of the pupal stage, which was determined in the same 

 way, was found to vary from 3 to 12 days, with an average of 5§ days 

 (Table IV). In a dry soil the larvae pupate at as great a depth as 4 

 inches below the surface, while in an extremely moist soil the pupal 

 cell is often formed within one-fourth to one-half inch of the top of 

 the ground, and in one rare instance it was found at the surface of the 

 ground just beneath some decaying vegetable matter. It can thus 

 be readily understood that a pupa near the surface of the gTound 

 would receive more heat from the sun's rays, and consequently would 

 develop more rapidly than one at a greater depth. This fact doubt- 

 less explains some of the variations in the combined lengths of the 

 egg, larval, and pupal stages in some cages, the records of which ap- 

 pear in Table I. For instance, in cage T-136 the combined lengths 

 of stages are shown to vary from 43 to 63 days, and in cage T-117, with 

 a mean temperature 5 degrees lower, adults were secured in 34 days It 

 is obvious that this presents a vulnerable point for attack in the life 

 of this pest, for if corn is weU irrigated the pupae will be formed near 

 the surface of the ground, and then if each irrigation is followed by a 

 careful, close but shallow cultivation, a goodly percentage of the 

 pupae are exposed to the sun and the drying effects of the air, and 

 hence killed. 



