170 
Psyche 
[June-September 
quite similar in Trochosa species; and once known for all genera of 
North American lycosids these ratios may help to set apart Tro¬ 
chosa, as well as other genera. 
Although the ecology and behavior of North American species of 
Trochosa have not been well studied, there is enough information to 
indicate similarities in habitats and phases of life history. All North 
American species of Trochosa inhabit edge of woods or open wood¬ 
land habitats (as do a number of their Palaearctic relatives). None of 
the American Trochosa are burrowers, such as Geolycosa and many 
species of Lycosa. Both Trochosa terricola and avara are often 
found under logs or stones, where they presumably molt and con¬ 
struct egg cases. These ecological and behavioral features also serve 
to separate species of Trochosa from many other lycosids. 
Species Groups. The structure of the male palpus and the female 
epigynum are often diagnostic at the generic level in spiders. In the 
case of Trochosa the genitalia delimit two species groups: ruricola, 
robusta, spinipalpis, and terricola on the one hand; and avara, gosi- 
uta, shenandoa, and parthenus, on the other hand. In Trochosa 
terricola the male is recognized by the long, thin embolus forming a 
loop at its distal end (Fig. 30) and the female by the broad inversely 
“T-shaped” epigynum (Figs. 13, 14, 16). Trochosa ruricola, robusta, 
and spinipalpis of Europe are very similar to terricola in genitalic 
structure (see Locket and Millidge 1951, Engelhardt 1964, Fuhn and 
Burlacu 1971). In North America terricola is the lone member of the 
ruricola species group and is easily differentiated from other species 
of Trochosa in this region by genitalic structure. 
Trochosa avara females are recognized by the epigynum which 
has the ends of the transverse piece directed anteriad (Figs. 20, 21). 
This feature is characteristic of females of the avara group (Figs. 18, 
23, 25, 27) and separates them from all other North American Lyco- 
sidae. A unique feature of the males in the avara group is the embo¬ 
lus which expands into a broad flattened, semi-transparent plate as 
it curves beneath the palea and then narrows to form a filament that 
coils into the concavity of the conductor (Figs. 34, 36, 39, 42, 45). 
The twist at the tip is reminiscent of the embolus in terricola. Des¬ 
pite the differences in structure of the male and female genitalia of 
terricola when compared with representatives of the avara group, 
the close correspondence in color patterns, particular morphologi¬ 
cal features, and certain ecological characteristics warrant their 
inclusion in a single genus. 
