352 
Psyche 
[Vol. 87 
are 3.0^.0 mm (Kaston 1978). Since A. subdolus females are 
2.2-2.6 mm in length, I predict that they are commensal or 
kleptoparasitic in the webs of P. oweni, not predatory on the adult 
females. 
Most of the observations of tropical kleptoparasitic Argyrodes, 
such as A. elevatus, have focused on their relations with large orb- 
weaver hosts. It is possible that even these “classically” kleptopara¬ 
sitic species behave as predators when they encounter smaller 
species of spiders and the spiderlings of large species. Two tropical 
Argyrodes, A. attenuatus (O. P.-Cambridge) and A. colubrinus 
(Keyserling) are known to spin a few dry, non-sticky threads which 
are used as resting places by ballooning spiderlings and male 
spiders, as well as by minute flies. These prey are not ensnared in the 
web; instead the Argyrodes uses its web as a platform on which to 
stalk these tiny prey (Eberhard 1979). In addition, Stowe and 
Vollrath report that Argyrodes will attack molting spiders of any 
size (Stowe, pers. comm.) 
Predator-Prey Interactions Between Argyrodes and Philoponella. 
The distribution of Argyrodes in solitary and commmunal webs 
of P. oweni raises some interesting questions about the searching 
behavior of Argyrodes and the value of P. oweni communal groups 
in defense against predators. 
1. Search behavior of Argyrodes. Argyrodes occur more frequently 
in communal webs of P. oweni. This may be because the Argyrodes 
encounter communal webs more frequently, or because they remain 
longer in communal webs once they find them. My sampling scheme 
did not distinguish between these two phenomena, but there is 
circumstantial evidence that both occur. 
Three Argyrodes females were collected from communal group 
#24 (one each on July 5, July 9 and July 14) and two from 
communal group #7 (one each on July 11 and 15). Since the 
Argyrodes were collected as soon as they were found, these are 
separate encounters. On the other hand, over the 1979 field season 
no more than one Argyrodes was ever found in any solitary web. 
This indicates that Argyrodes are encountering communal webs 
more frequently than solitary webs. This may be because communal 
webs are larger, because they offer more effective cues to searching 
predators, or because both Argyrodes and communal Philoponella 
are selecting similar environmental features. 
