Crabro cephalotes 297 



ejected together with the frass from new tunnelling operations, 

 but never otherwise. 



Continuous observation of work that went on for many hours 

 a day for about three weeks was, of course, impossible, but on 

 several days, especially during the week Aug. 18 — 25, operations 

 were watched for spells of an hour or two at a time, and the exact 

 times of ingress and egress carefully noted. The notes which 

 immediately follow especially concern wasp No. 1. 



The hole was sometimes clear, sometimes choked with "saw- 

 dust." After watching for a time the "sawdust" would be seen to 

 heave up and form a mound over the hole. Then the wasp would 

 emerge and proceed to remove the frass, butting it away from the 

 neighbourhood of the hole with its head. Sometimes in the course 

 of its excavations the wasp would emerge, fly away for a time, and 

 return empty handed to resume its digging. 



On Aug. 19 it was seen to be carrying home flies, and the per- 

 formance was watched for an hour, and the following times were 

 noted: 



Returned with fly, 9.37, 9.48, 10.18, 10.31. 

 Emerged, 9.40, 9.55, 10.25, 10.39. 



Thus four flies were caught in the hour, and the times spent in 

 capturing three of them were 8', 23' and 6' respectively, while 

 3', 7', 7' and 8' were occupied in packing the four flies into the 

 burrows. To find, capture, paralyse and bring home the right kind 

 of fly in six minutes strikes one as a remarkable feat. From further 

 observations it appeared that the operation usually occupied about 

 a quarter of an hour. None but "hover flies" (Syrphidae) were 

 taken by any of the wasps, and the prey was generally Syrphus 

 halteatus, a species almost as large as the wasp itself. It was, 

 nevertheless, carried with perfect ease, arranged longitudinally, 

 head foremost beneath its captor, and, I believe, venter to venter. 

 No preliminary examination of the hole was ever made before 

 carrying the fly in, such as Fabre has recorded in the case of some 

 wasps. About noon on Aug. 21 this wasp apparently ceased 

 workino;. There were no signs of activitv that afternoon nor the 

 following morning. 



On Aug. 22 about 3 p.m. a wasp (wasp No. 2) was seen to come 

 out of the woodpecker's hole and alight on the top of the log, 

 which it proceeded to explore. It found No. I's burrow and 

 entered it for a short distance, after which it flew away. Nothing 

 further was noted till the evening of Aug. 23, when on returning 

 home at 5.30 I noticed a heap of frass on the top of the hole. At 

 6.20 a wasp arrived and after pointing at the main entrance, 

 seemed to change its mind and alighting on the top, entered No. 

 I's hole. Its behaviour convinced me that it was not No. 1, but it 



