1979] Matthews, Hook & Krispyn — Behavior of Crabro 159 
parasitized cells was 16.7% in April, 1978. Miltogrammine flies col¬ 
lected or reared from the boiler site belonged to two genera, Seno- 
tainia spp. and Sphenometopa sp. At north beach no miltogram¬ 
mine flies were seen and no parasitized cells were found. Possibly 
the strong and persistent winds blowing along the north beach cliffs 
dispersed the parasites. Also, it may simply be that it was less “prof¬ 
itable” for the flies to invest time and energy battling the winds to 
locate the widely dispersed nests. At the road site in October, 1978, 
parasite flies were common, but no parasitized cells were found. 
Two flies collected here were Senotainia trilineata (Wulp) and Sphe¬ 
nometopa tergata (Coquillett). 
Perhaps correlated with the presence or absence of parasites, the 
behavior of provisioning females differed strikingly. Prey-laden 
females returning to open nests at the boiler site made a distinctive 
approach flight in which they would approach the nest entrance and 
then slowly drift backwards away from the nest. Some females were 
observed to retreat as much as 3 m in a rather pulsating flight about 
6-10 cm above the substrate. This conspicuous flight behavior usu¬ 
ally attracted 1 to several miltogrammine flies who. followed in close 
synchrony with the movement pattern of their potential host (hence 
the very apt common name = satellite flies). Having lured the para¬ 
sites off some distance, the female suddenly and unpredictably 
zoomed forward in a “bee line” plunging headlong into her open 
entrance and leaving the flies behind, somewhat disoriented. The 
same behavior was observed on the mainland site, a flat expanse of 
sandy soil constituting a turnaround area at the end of a dirt road. 
Several miltogrammine flies were sighted at this area. Comparable 
behavior was never seen in females nesting at north beach or 
Wamassee Creek, and may therefore represent a response to 
increased parasite pressure at the boiler and mainland sites. Evans 
(1960) records the same behavior for this species when pursued by 
miltogrammines. Closely similar anti-parasite provisioning behav¬ 
ior has also been described for an unrelated sphecid, Philanthus 
crabroniformis F. Smith by Alcock (1974). 
On at least one occasion a Senotainia was observed to follow a 
female wasp into her burrow. Nests were typically left open during 
provisioning, but at least two females made weak temporary outer 
closures between provisioning trips and “crashed” directly into their 
nests upon returning. This behavior may have been a response to 
parasite pressure. Several parasitized cells contained more than one 
