THE BIOLOGY OF THE ALDER FLEA-BEETLE. 255 



Nevertheless there is great variation in the length of time 

 which different individuals require for reaching maturity. This 

 is true even in the case of larvae hatching from a single egg 

 cluster, or from different egg clusters but on the same day. For 

 example, from eggs which hatched on July 17, 11 prepupae were 

 obtained on August 11, 25 on August 13, 4 on August 14, and 

 11 on August 15; 9 pupae were removed on August 17, 5 on 

 August 19, 4 on August 20, 1 on August 21, and 1 on August 

 22. 



The following is cited as a typical life-history: 



6 eggs which were deposited on July 22 (1914) hatched on July 30. 

 The larvae molted to the second instar on August 11. 

 The larvae molted to the third instar as follows : 



1 on August 19 ; 1 on August 21; 2 on August 23; 2 on August 24. 

 The larvae entered the soil as prepufae, as follows: 



1 on August 27 ; 1 on August 28 ; 1 on August 31 ; 3 on September 1. 

 Pupae were formed as follows : 



3 on September 3 ; 2 on September 5 ; 1 on September 6. 

 Adults emerged as follows : 



1 on September 13; 1 on September 14; 1 on September 15; 2 on 

 September 16; 1 on September 17. 



SEASONAL HISTORY IN MAINE. 



The earliest date on which the writer has found eggs of the 

 alder flea-beetle in Maine is June 16 (1915), but since he has 

 collected recently hatched larvae on June 18 (1915), eggs must 

 be deposited at least as early as June 10. The maximum period 

 of egg deposition is early July. The latest date on which eggs 

 were deposited in the laboratory is July 29 (1915), when only 

 three eggs were obtained from many females which had been 

 ovipositing freely. No unhatched eggs were found in the field 

 at a later date. The oviposition period extends over a period 

 of about a month and a half : from mid-June until late July. 



Just hatched larvae were common on June 20 (1915). Lar- 

 vae may be found commonly in the field as late as mid-August 

 in years when this insect is abundant. No larvae have been 

 found in the field later than August 24 (1914), although the 

 writer has had them in the laboratory as late as August 30 

 (1914). The great majority of the larvae become full grown 

 in late July or the first half of August. 



The earliest date on which the writer has obtained pupae 

 of this species is August 5 (1914). Without doubt this is much 



