PREY CAPTURE BY DKYMUSA DINORA 
(ARANEAE, SCYTODIDAE) 
By Carlos E. Valerio* 
Departamento de Biologia. 
Universidad de Costa Rica 
Introduction 
The family Scytodidae includes at present three genera, of which 
Scytodes and Loxosceles are well known because of their specialized 
prey-capturing strategies. Scytodes species eject a sticky substance 
(perhaps similar to the silk from the spinnerets) from the chelicerae 
at a considerable distance to trap the prey (Bristowe, 1931; Mc- 
Alister, i960). The species of Loxosceles have developed a very 
effective venom capable of subduing strong prey almost instantly 
(Hite et al ., 1966). This venom affects even vertebrate tissues, 
including those of man (Bucherl, 1961). 
The genus Drymusci, a small and poorly studied group, is morpho- 
logically more closely related to Loxosceles than to Scytodes. It 
lacks the high carapace, and possesses a colulus ; also the male bulbus 
is located at the tip of the tarsus (Valerio, 1971). The forest-dwell- 
ing species of D. dinora Valerio, which lives exclusively under logs 
utilizing crevices and horizontal tunnels in the decomposed wood 
(Valerio, 1971), exhibits highly specialized behavioral patterns never 
observed in other spiders. The permanent web, composed of a few 
tangled threads, seems to alert the spider to the presence of prey and 
to restrict the movement of prey. Clearly, this type of construction 
represents a very primitive conditon in the phylogeny of the web 
(Kaston, 1966). 
Materials 
Several mature and immature specimens of D. dinora , of both 
sexes, were collected in a wet lowland forest in southwestern Costa 
Rica and kept individually isolated in 12-dram vials ( 100 X 22 mm), 
at IOO percent humidity and 24.5 zb 0.2°C. 
Observations 
This species is remarkable in two aspects of its attack behavior, 
departing from all known patterns: for large prey the spider spins 
*1 wish to thank Dr. Herbert W. Levi (Museum of Comparative Zoology, 
Harvard University) for his critical review of this manuscript. 
Manuscript received by the editor January 5, 1974. 
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