330 THE SCOTTISH NATURALIST 



the chill of the morning air. So also in Lubbock's case the 

 cessation of work appears to have an approximate relation 

 to the time of sunset. The last visits paid by his marked 

 wasps varied from 5.14 to 6.43 P.M. during the latter half 

 of September, when the sun set between 5.50 and 6.5 r.M. 

 There is some evidence that in fine weather the working day 

 tended to be longer than on dull or stormy days. 



I made no effort to check the commencement of the 

 day's work (in July the sun rises about 3.30 A.M. !), but I was 

 struck by the late hour at which wasps might be seen abroad. 

 The following observations were made to verify a general 

 impression. A dull, damp evening was chosen in the belief 

 that the tendency would be all for the wasps to return early 

 to the nest. The sun gave no evidence of its presence 

 during the day, but set officially at 8.26 P.M. The maximum 

 shade temperature, recorded between 9 A.M. and 9 P.M., was 

 65° F., the minimum 45° F. 



At 8 o'clock the activity of the nest seemed to be normal ; 

 numerous wasps were either making for or departing from 

 the entrance. At sunset there was still much activity, but 

 the numbers of departing wasps had fallen almost to zero. 

 Darkness came on rapidly after sunset. At 9 o'clock it was 

 difficult to distinguish individuals, but there was still a 

 considerable amount of traffic, an almost continuous stream 

 of wasps returning in small parties of two, three, or four at a 

 time. No wasps were leaving the nest. At' 9.30 there 

 was a great falling off in activity, and at 10 P.M., when it 

 was quite dark and observations had to be carried on by 

 aid of a hurricane lamp, no wasps were seen returning and 

 the nest appeared to be wrapped in wasp slumber. To 

 check this observation, however, I gently but firmly blocked 

 the entrance to the subterranean tunnel with a pad of cloth 

 on which a few drops of cyanide of potassium solution had 

 been sprinkled. On paying an early visit next morning, I 

 was surprised to find 30 dead wasps grouped about the 

 blocked entrance, which they had vainly been endeavouring 

 to force. These revellers must have returned after I left 

 the nest in total darkness at 10 p.m. 



Resourcefulness. — In a preliminary and unsuccessful 



