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126 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 
Tl. 
The third group of Orbweavers making vertical webs is composed of 
those which retain the open hub. Among these are our indigenous species 
__ of the genus Acrosoma. These are found in the neighborhood of 
pink with philadelphia, and are distributed very generally throughout the 
bie ss Middle, Northern-Middle, and Southern States, east of the Rocky 
Mountains. The favorite site for their snares is a large open 
space between two bushes or trees, or between the diverging branches of 
the same. I have most frequently found them in the margins of an open 
grove, wood, or forest. As a rule they swing their nets at a considerable 
height, so that one’s face comes in contact with them while passing through 
the woods. ‘The foundation lines are frequently of considerable length, four 
or five feet, or even more. The delicate orb swung between them is a very 
pretty sight as one sees it outlined against the sky, showing through the 
vista of the opening trees. (Fig. 111.) 
The three species common to our neighborhood are Acrosoma rugosa, 
spinea, and mitrata.t They are all characterized by abdomens which present 
upon the dorsal surface spines of greater or less length and hard- 
ness. ‘These spines are more decidedly developed upon the first 
two named species. In the last named species, the Mitred spider, 
the spinous processes are small, and the integument is not so tough. 
All the three species make substantially, and I might say almost pre- 
cisely, the same sort of web. The shape of the snare is usually quite orbic- 
ular, nearly always approaching a circle more nearly than that of most 
species of Orbweavers. The number of radii is very great, amounting at 
times to as many as eighty, and the number of spirals is corre- 
spondingly large. ‘The orb itself is not very large, generally 
being within six inches in diameter rather than above. It re- 
sults, therefore, that the spiral space presents a remarkably close texture of 
checkered openings between the cross lines. The free zone, which in the 
typical Epeira net contains no lines crossing the radii, is always occupied 
in this genus by the lines of the notched zone, which wind in three or four 
comparatively widely separated concentrics through the entire free zone. 
These take the place of the notched zone of the Epeira orb, whose con- 
centrics are wound close up to the hub. 
The hub, as has been stated, is always open, and within it the spider 
is usually found hanging with its legs outstretched, grasping the marginal 
circumference of the hub. Spinea and Mitrata hang in a position closely 
resembling that of the ordinary Epeira, that is to say, with the head 
Favorite 
Sites. 
Character 
of Orb. 
1 As I have heretofore shown (Proceed. Acad. Nat. Sci. Philada., 1888, page 5), the names 
of these species as given by Walckenaer are entitled to priority. They will probably be 
known respectively as Acrosoma gracilis (rugosa), A. saggittata (spinea), and A. reduviana 
(mitrata). 
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