290 
Psyche 
[September 
Examination of Table 3 shows clear differences in prey preference 
among the members of the genus Trypargilum; these appear to 
parallel the morphological species groupings. Three groups, Nitidum, 
Politum and Punctulatum, show decided preferences for snare- 
building spiders (Araneidae, Theridiidae, Tetragnathidae, Liny- 
phiidae, Dictynidae) while members of the Spinosum group take 
predominantly wandering or vagabond spiders (Salticidae, Thomi- 
sidae, Oxyopidae, Lycosidae, Anyphaenidae, etc.). Furthermore, 
members of the first three groups do not appear to take prey across 
as wide a spectrum as do members of the Spinosum group (2-4 
families as opposed to 6-1 1 families). One family, the Araneidae, 
is preyed on in varying percentages by every Trypargilum species 
for which data are available. Strikingly, T. politum appears restricted 
almost entirely to tw~o genera in this family, Neoscona and Eustala 
(Muma and Jeffers, 1945), suggesting quite specialized hunting be- 
havior. Within the Spinosum group, T. clavatum exhibits a decided 
preference for Salticidae and T. arizonense for Thomisidae, while 
T. texense and T. johannis take approximately equal numbers of 
Salticidae, Oxyopidae and Araneidae. Predicting from the table, 
we would expect T. calif ornicum and T. spinosum to also prefer 
spiders of the vagabond or wandering type. 
Cocoon Structure in Trypargilum. Cocoon structure insofar as 
known also agrees with the groupings of Richards (1934) and Sand- 
house (1940). Krombein (1967) has obtained data for all the North 
American representatives of the Nitidum and Punctulatum groups 
and for two species in the Spinosum group. Data on T. politum 
and T. arizonense are presented here. 
The Spinosum group, to which T. arizonense belongs, is charac- 
terized by cocoons with a truncate anterior end and a distinct pale 
collar; T. johannis and T . clavatum cocoons have, in addition, a 
weak nipple development which is absent in T. arizonense. While 
there are at least four references to nests of T. texense in the litera- 
ture, no description of the cocoon is available; based on the trend 
shown by the known species’ cocoons, we would predict this species 
(as well as T. calif ornicum and T. spinosu?n ) to have cocoons with 
the anterior end truncate and collared. 
Cocoons of species belonging to the Nitidum group have the 
anterior end either rounded ( T. tridentatum tridentatum , T. t. arch- 
boldi ) or truncate with a prominent nipple ( T. collinum collinum, 
T. c. rubrocinctmn) . There is no trace of anterior collar develop- 
ment as is characteristic of the Spinosum group, although nipple 
development occurs in representatives of both groups. 
