1972] 
Fergusson — Hypochilus thorelli 
1 8 1 
and above in the Appalachian Mountains of North Carolina, Ten- 
nessee, Georgia, and Alabama, and in the Cumberland Plateau of 
Tennessee and Kentucky. Kaston (1948) reported that Petrunke- 
vitch introduced FI. thorelli into Meshomasic State Forest in Con- 
necticut in 1932, and that they were “holding their own” in 1937. 
Petrunkevitch (1932) gave the Appalachian distribution as a 
triangle with apices at Blowing Rock, North Carolina, Tallulah 
Falls, Georgia, and Maryville, Tennessee. The line from Tallulah 
Falls northwest to Maryville has been extended farther into Georgia 
and Alabama. The Appalachian populations are separated from the 
Cumberland populations by the broad valley of the Tennessee River. 
While the distribution of H. thorelli in the Appalachians is appar- 
ently limited to the east, south, and west by low elevations, no such 
geographic barrier is apparent that would limit its northward dis- 
tribution, or the southward distribution of H. gertschi, known from 
West Virginia and northwestern Virginia. Yet Petrunkevitch 
(1932) and Hoffman (1963) searched in favorable habitats in the 
“isthmus” of western Virginia, and were unable to find any pop- 
ulations. 
Habitat 
The optimum habitat for H. thorelli in North Carolina is in stream 
gorges in humid deciduous forests at elevations of 600 to 1100 m 
(2000 to 3600 ft). Webs are built predominantly on sheltered rock 
ledges. The undersurfaces of stream bridges and logs overhanging 
or close to stream banks are also occasionally inhabited. 
The availability of web substrate is a factor which limits local 
distribution. Stable overhanging or vertical surfaces with a number 
of projections or nearby plants for guy line attachment are necessary. 
Humidity is apparently the most important factor limiting local 
distribution. H. thorelli webs are more abundant close to a stream 
than farther away. Well-shaded ledges are more likely to be inhabited 
than poorly-shaded ones. Where the ledges are well-shaded, the webs 
are built at any place providing good attachment points. On poorly- 
shaded ledges webs are built close to the ground, usually behind low 
vegetation where increased shade and plant transpiration keep the 
humidity higher. 
Marginal habitats located included an unshaded roadside ledge 
100 m across cleared land from the nearest stream (Graham County) 
and a ledge in dense spruce-fir forest on the side of Clingman’s Dome 
at an elevation of 1891 m (6200 ft). 
Hypochilus was observed from 397 to 1891 m (1300 to 6200 ft), 
but is rare above 1370 m (4500 ft). 
