Spiders and their webs are predictable sources of insect cadavers.
A small number of animals regularly exploit this resource, either as
kleptoparasites or commensals, depending on whether symbionts
compete for the same prey (see Robinson and Robinson, 1977, for
more detailed terminology). Among the thieves are specialized
spiders (citations in Vollrath 1979a, 1979b), mature male and
juvenile spiders (Stowe 1978, citations in Nyffeler and Benz 1980),
Hemiptera (Davis and Russell 1969), a hummingbird (takes webbing
in addition to small insects, Young 1971), panorpid scorpion-flies
(Thornhill 1975), Lepidoptera larvae (Robinson 1978), wasps
(Jeanne 1972), damselflies (Vollrath 1977), and a handful of flies
(reviews in Knab 1915; Bristowe 1931, 1941; Lindner 1937; Richards
1953; Robinson and Robinson 1977). Only a few of the reports on
Diptera kleptoparasites originate from North America (McCook
1889, Frost 1913, Downes and Smith 1969). With a single exception
(Downes and Smith 1969), all of the previously described kleptoparasitic
flies belong to the Brachycera and Cyclorrhapha. We
report here on a surprisingly diverse kleptoparasitic Diptera fauna
in north central Florida with a cecidomyiid (Nematocera) as its
dominant member.