OBSERVATIONS ON THE WEB AND BEHAVIOR OF 
WENDILGARDA SPIDERS 
(ARANEAE: THERIDIOSOMATIDAE) 
By Jonathan Coddington 1 and Carlos E. Valerio 2 
Introduction 
Theridiosomatidae are a small family of mostly tropical spiders 
that are related to the common orb-weaver family Araneidae. It is 
known that theridiosomatids spin modified orb-webs, but only the 
web of the holarctic Theridiosoma gemmosum (C. L. Koch) has been 
studied in any detail (McCook, 1889; Wiehle, 1931). Recently we 
independently discovered the unusual webs of some tropical theridio- 
somatid spiders that the senior author later identified as belonging to 
the genus Wendilgarda. The architecture and operation of these webs 
are unique among known spider webs. The sticky lines of the web are 
connected to the surface films of moving streams, and moreover are 
under considerable tension, more tension than can be accounted for 
by the action of water surface tension on an inert filament alone. The 
attachment of the sticky lines to the water surface is integral to the 
operation of the web. The sticky lines function by ensnaring insects 
that are themselves on the surface film of the water and are floating 
downstream. 
Materials and Methods 
Our observations refer to populations in Costa Rica (OTS Finca 
La Selva, Heredia; Punta Llorona, Puntarenas), Guatemala (Santo 
Tomas, Izabal), and Honduras (Nuevo Rosario, San Juancito). 
Conclusive identifications of these spiders are not possible until the 
genus is revised (Coddington, in prep.), but our observations refer to 
at least three species, all of the genus Wendilgarda. Voucher 
specimens are deposited in the Museum of Comparative Zoology, 
Harvard University. Behavior of the spiders was observed by shining 
a headlamp obliquely at the subject and using a simple 5X handlens. 
Museum of Comparative Zoology Laboratories, Harvard University, Cambridge, 
Mass., 02138, USA. 
2 Escuela de Biologia, Universidad de Costa Rica, Costa Rica 
Manuscript received by the editor June 20, 1980. 
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