28 PEOCEEDINGS OF THE NATIONAL MUSEUM vol. 68 



quudrifasciata under observation at Adaton, Mississippi. Several 

 visits were made to this colony during the next few weeks until 

 the extreme dry weather and heavy traffic over the road in which 

 the colony was located obliterated all traces of the wasps. Adults 

 of vigilans were abundant about this colony for several weeks. The 

 fly was frequently observed in low zigzag flight over the sand from 

 which it would alight at frequent intervals on small sticks or blades 

 of grass. Intense interest was displayed by females in Bembecids 

 returning to their nests. Wliile the wasps were in flight about their 

 burrows, the flics were frequently seen hovering cautiously about a 

 foot behind them. The presence of the flies seemed to annoy the 

 wasps, which would frequently turn on them and attempt to drive 

 them away, but such attempts were futile, as the flies, no longer 

 pursued, would immediately return. The fly was seen to dart swiftly 

 into the burrow after the Bembicid, and to emerge again, almost 

 immediately, and before the reappearance of the wasp. After 

 depositing its prey, the wasp would emerge, cover up the entrance to 

 its burrow and fly away. In this connection, it may be noted that 

 quadnfasciata usually closes its burrow each time that it leaves it, a 

 precaution which serves to repel parasitic flies during its absence but 

 very clearly affords no protection against those with a habit like that 

 of vigilans, which enters the burrow during the visits of the wasp. 

 Smith has observed that quadrifasciata does not invariably close its 

 burrow when leaving it, as he has on several occasions unearthed 

 several well stocked cells left conspicuously open. Such nests, while 

 especially vulnerable to attack, do not seem to be sought out by 

 vigilans. It was observed that the wasp, carrying prey, was the 

 principal cause of excitement and activity on the part of the flies and it 

 is quite likely that in this species, this combination is necessary for the 

 stimulation of the female to larviposition. 



A number of the nests of quadrifasciata were unearthed and the 

 contents, consisting of the egg of the Bembicid in the midst of Pen- 

 tatomid and Coreid nymphs, were carefully removed. No evidence 

 of the maggots was found in the field, but in one lot, maggots were 

 unexpectedly encountered a day or two after removing the contents 

 of the cell to the laboratory, and from them the adults oi vigilans were 

 reared. The bodies of the nymphs were rapidly reduced by the 

 maggots to a putrid mass in which they reveled like Sarcophagid 

 scavengers in decomposing flesh. In the one completed nest of 

 quadrifasciata from which this parasite was reared, the maggots did 

 not show up until after the egg of the wasp had hatched. Maggots of 

 Senotainia and grub of Bicyrtes were both observed feeding on the 

 provisions of the nest on one day, but on the succeeding da\', the grub 

 had succumbed, either to direct onslaught by the maggots or the 

 unfavorable conditions produced by them, but at any rate, not to 



