THE HORSE-RADISH FLEA-BEETLE. 11 



The length of the egg-laying period, as shown by the record of an 

 individual given above, is about 75 days, from the middle of May to 

 the first of August. It is certain that this beetle emerged in 1014, 

 probably in August or the first of September, and it is fair to as- 

 sume that the species would have lived longer in nature had it not 

 been killed by predators, parasites, disease, or the like. This shows 

 the species to be exceptionally long-lived, living about a year in the 

 adult stage. 



The fact that the males are as long lived as the females may pos- 

 sibly be due to the fact that copulation is necessary at intervals dur- 

 ing the egg-laying period. 



RECORD OF EXPERIMENTS IN 1916 AT GREEN BAY AND MADISON. WIS. 



April 24, a pair of beetles confined with horse-radish plants. 

 April SO to May 5, copulation observed. 

 May 11, 15 eggs deposited within 24 hours or less. 



May 12, 12 eggs in fold of leaf ; might have been overlooked the day before. 

 May 17, 31 eggs found deposited since May 12. 

 May 22, 24 eggs found over Sunday, about 48 hours. 

 May 24, 20 eggs and copulation observed. 

 May 25, 25 eggs observed. 



May 29, 48 eggs obtained over Sunday in about 48 hours. 

 May 31, moved to Madison, Wis. 



June 4, 66 eggs obtained since May 30 ; copulation observed. 

 June 9, 44 eggs, approximately, observed since June 4. 

 June 14, 60 eggs found in 24 hours. 

 June 15, 49 eggs seen in about 24 hours. 

 June 21, 27 eggs obtained since June 15. 

 June 24, 44 eggs seen in 24 hours. 



June 27, 48 eggs deposited within 24 hours or less. At this point the obser- 

 vations were discontinued. 



HATCHING RECORD. 



The same difficulty which was experienced in 1915 in the hatching 

 of the eggs was observed this year. Of the entire number of eggs 

 obtained from the female whose record is given above, a total of 513, 

 the following hatched : 



June 4, 1 egg deposited May 17 hatched, 17 days. 

 June 9, 1 egg deposited May 17 hatched, 22 days. 

 June 14, 7 eggs deposited June 9 hatched, 7 days. 



As noted in the table of the 1916 records (Table 3), some of the 

 larvae died and only a few of these cases are mentioned; the re- 

 mainder, being unimportant to the records, are not recorded. All 

 dates on which observations were made are given. 



