Rhynehaet — Life-History and Bionomics of the Flax Flea-Beetle. 525 



Prior to the emergence of tliese adults, and from the last week of June, 

 few beetles are seen, because most of the old overwintering brood die before 

 July, none having been found in the field after the middle of July, 1921. 

 The newly emerged beetles feed for some time before going into hibernation, 

 but they do not pair, nor do the females lay eggs ; hence the species pro- 

 duces only one extended brood annually. If, however, the adults are caged 

 throughout the winter on flax growing in a heated house, a brood will 

 emerge early in May, as shown by an experiment conducted during the 

 winter of 1920-21. 



(rt) Pairing of the Adults. — Actual pairing has not yet been observed, 

 although a careful search was made from the 1st of May onwards. It is 

 probable that general copulation had been effected prior to that date; and 

 the fact that egg-laying commenced early in May would point to such having 

 occurred. The warm weather which prevailed during late April of 1921 

 would, no doubt, influence early emergence from hibernation, and, simul- 

 taneously, early mating. Adults of Chri/somela staphylea and Bembidium sp. 

 were observed in copulation as early as the first week of April. It is hoped 

 to make earlier search for copulating adults next season, and in the winter 

 quarters as well as on flax seedlings. As already indicated, no instance of 

 mating such as that reported among some species of Chrysomelidae (38) has 

 been observed in the newly emerged beetles prior to hibernation. 



(b) Oviposition. — During the first week of May, 1921, several beetles 

 were seen to be noticeably stouter in the abdominal region, and when such 

 individuals were dissected, many light-yellow and nearly mature eggs were 

 found in the ovarian tubes. These, then, are the gravid females, and as such 

 can easily be distinguished from the smaller-bodied and more agile males. 

 Eggs were first seen on the 16th May during the season of 1921 in one of 

 the laboratory cages, and in the open field four days later. The latter had 

 the appearance of having been deposited for some days, so that it is likely 

 egg-laying commenced in the open about the 15th May, 1921. Observations 

 on the life-history during the season 1920 were not commenced until July ; 

 but it is interesting to note that eggs were deposited by a caged female that 

 season as late as the 10th July. No eggs were seen in the laboratory cages 

 or in the open field after the 11th June, 1921, so that egg-laying may be 

 said to have occupied about one month during season 1921, and to have 

 extended from the first week in May to the first week in June, or roughly 

 one month earlier than the single instance of egg-laying recorded in 1920. 



Normally, the eggs are always deposited in the soil, but the actual posi- 

 tion with reference to the flax plant does not appear to be important, as eggs 

 have been found at different distances from the nearest plant. Eggs have 



