S. A. Arendsen Hein 247 



pupae-dish, in which the emergence of the beetles was awaited, and as 

 soon as these came out they were examined. Sometimes in ^i, but 

 as a rule in the F^ generation the beetles which did not possess a given 

 character had to be removed. Those which showed it had to be kept for 

 further breeding. I had to be quite sure, however, that the beetles had 

 not already copulated before, otherwise a separation would not have been 

 of any use. The pupae-dishes were daily inspected for the presence of 

 beetles ; so the beetles examined were at most 24 — 30 hours old. 



The question to be answered was: how much time will elapse 

 between the beetle being hatched and its copulation. If copulation 

 should take place within + 36 hours, it would be necessary to arrange 

 a male and a female pupae-dish for every culture. An answer in this 

 sense would cause not only a doubling of the number of the dishes, 

 and of incubator space, but also a not inconsiderable increase of work 

 (separation of the sexes). The problem was solved by the following 

 experiment. Some beetles from the moment they were hatched were 

 kept two by two (</ and $ ) in small pots in the incubator for 72 hours. 

 After this time all the males were removed, and the females kept for one 

 month for the gathering of eggs, if any. 



From this series of 10 pairs, eggs were obtained from only two 

 females; one producing one egg, the other eight eggs. The nine eggs were 

 apparently sterile as they produced no larvae, and after some time all 

 were shrivelled. They were probably virginal eggs, which some females 

 will produce when prevented from mating. The result of this experiment 

 leads to the conclusion that no copulation takes place within thirty 

 hours after the hatching. 



