ee a ee ee ee ee ee 
vu . rom 4 lig 2 
zone are cut off above, 
COMPOSITE SNARES AND SECTORAL ORBS. 133 
The orb of Labyrinthea is a delicate and beautiful structure. It is not 
large in size, usually measuring six or seven inches at the longitudinal axis 
and five or six at the lateral. The largest web I ever saw was 
twelve inches in diameter.!. Within this space are disposed a 
large number of finely spun radii and spirals, the former some- 
times numbering as high as seventy-five, the latter exceeding eighty. The 
spirals, as is common in orbwebs, are more numerous below than aboye the 
hub, but this difference is very marked in the web of Labyrinthea, some- 
times being as great as three to one, and even six or seven to one.? The 
spirals in the lower part of the orb are not complete circles, but are looped 
The Orb 
Described 
in, the lines terminating at the sides. . This feature is sometimes seen 
in full orbwebs, and is habitual in sectoral orbs. (See Fig. 121.) 
The diminished number of spirals at the top of the orb is in part 
due to a peculiar feature of the snare, which at least suggests that com- 
bination of characteristics of full orb and sectoral orb al- 
Cems ready alluded to. This fea ture results, first, from the posi- 
tion Cen- |. eee pias f : ; 
tral Space tion of the spider’s domicile behind the orb, making it nec- 
essary that the 
the snare in order to give 
its outer surface ; and, sec 
direction of the trapline 
trapline should penetrate 
the spider admission to 
ond, from the slanting 
which compels a larger 
opening than would oth erwise be required. This 
is illustrated at Fig. 117, which shows the centre 
of the orb from behind FQXQe U4 ee and above with a special 
view to the connection 4 Tae ous x way of the trapline with the 
hub, and its relations to ; the spirals.? It will be 
seen that the unbeaded spirals of the notched 
leaving a triangular open 
space somewhat like the (yy “howineachal wenina free radius of a sectoral 
orb. This opening is larger or less according 
to circumstances; it may be increased by the trapline impinging upon 
the spiral space, thus leaving but a few continuous spirals at the top of 
the orb. The spider when seeking prey runs through this opening, under- 
neath the overspun arch of spiral lines, to the outer face of the orb upon 
which the insects are ensnared. It returns along the same path to the 
tent with the captured insect. 
A 
CORY) 
PRON 
‘The following measurements in inches show ordinary sizes: 7 inches long by 6 wide; 
Ox bs 656; 9x 7) 6x 4hs 12x 12, 
* The following counts will illustrate this: No. 1, radii, 55; spirals, 31 above, 82 below. 
No. 2, spirals, 8 above, 55 below, 47 at the sides. No. 3, radii, 75; spirals, 80. 
’ Measurements of Fig. 117, orb 9 in. long by 7 wide; hub } in. long, $ wide; centre 
of hub 2} in. (about one-third the length of the orb) from the top margin of the orb. 
The hub is meshed, oval, narrowed at the top. The notched spirals fill the Free space, 
three being close to the hub, the others widening as they wind. Traplines about 2} 
in. long. 
