1980] Sivinski & Stowe — Kleptoparasitic cecidomyiid 343 
to safely hang on the viscid spiral lines of Nephila clavipes webs, 
perhaps by utilizing the comparatively “dry” areas between glue 
droplets. The Uganda chloropid Anomoeoceros punctulatus stays 
close to areneids and avoids the web by hovering, even in strong 
winds, directly beneath the spider (Ismay 1977; chloropids are 
acalypterates that may be kleptoparasites, parasitoids or both of 
spiders, Bristowe 1941; Harkness and Ismay 1975; Robinson and 
Robinson 1977). Perching upon the spider itself seems energetically 
less expensive. Among Florida kleptoparasites, only Phyllomyza sp. 
appeared to be phoretic. Phoresy is found in several Old World and 
neotropical milichiids and chloropids (Bristowe 1931, 1941; Rich¬ 
ards 1953; Robinson and Robinson 1977; Ismay 1977). Even on the 
spider, competition might drive individuals closer to the source of 
nourishment and could explain the striking concentration of flies on 
the cephalothorax of a Nephila clavipes illustrated in Robinson and 
Robinson (1977; note that Anomoeoceros punctulatus hover near 
the jaws of hosts; see Ismay 1977). 
Spatial distribution 
The distribution of milichiids is distinctly clumped. We observed 
dozens of spiders over a period of several weeks and found only four 
with milichiid kleptoparasites. Of these, however, ten flies were 
present in one instance, five in another, and single flies in the other 
two (see also apparent clumping in Robinson and Robinson 1977; 
McCook 1889; Bristowe 1931, 1941; Richards 1953). Perhaps some 
spiders, or their prey, may be more attractive. In most descriptions 
of milichiid kleptoparasitism, the flies were found feeding on 
Hymenoptera prey (Clausen 1940; Knab 1915; Bristowe 1931, 1941; 
Richards 1953; Robinson and Robinson 1977; Ross, pers. comm.). 
We discovered milichiids on the following prey items: a vespid wasp, 
an unidentified Hymenoptera, and a pentatomid bug. A preference 
for Hymenoptera prey would be a curious attribute for an orb 
weaver associate. Hymenoptera do not appear to consitute a large 
part of the average spider’s diet in our area or in other studies (e.g., 
0.4% by weight for Argiope argentata, Robinson and Robinson 
1970). It is possible that an easily tracked substance is released which 
attracts the flies during the capture or consumption of Hymenop¬ 
tera. On the other hand the crab spider host Misumena spp. 
(Thomisidae) frequently preys on bees (Biro 1899; Bristowe 1941). 
Desmometopa sordida was the kleptoparasite in a number of the 
