270 
A halos — Latrodectus 
[1962 
pyriform and its most frequent size is about io mm. The sac is formed 
by threads 8 microns in diameter. They form a tissue, not very dense, 
but tight, that constitutes a thin cover, soft to pressure of the fingers. 
On the surface of the egg-sac we can observe numerous little web 
pompons that give a characteristic granulous aspect (Fig. 3). These 
little pompons are made by the spider with the hind legs; they are not 
firmly joined to the surface of the egg-sac and they usually fall off 
with handling. 
Latrodectus No. 3 : The egg-sac of this spider generally has the 
same shape as the one mentioned above, even though it sometimes 
changes, up to the point of presenting the aspect of an elongated pear ; 
its size varies, but it is always bigger than the former species, reaching 
21 mm in its biggest diameter. The sac wall is thicker and is formed 
by threads of a diameter of about 16 microns. These threads form a 
tight tissue, with a parchment texture that makes the egg-sac resistant 
to pressure. The egg-sac completely lacks pompons or any other orna- 
ment on its surface (Fig. 4). 
Latrodectus No. 4: The egg-sac is white, pyriform, and its common 
size is about 10 mm. The sac-wall is thin, with threads of about 8 
microns in diameter forming a less compact tissue. On this cover the 
spider weaves a coat about 3 mm thick, of loose tissue, that gives; the 
egg-sac the appearance of a spherical woolen tuft (Figs. 5, 6). 
We can also observe that Latrodectus No. 1 differs from the other 
species in its egg-sac. Its size is always smaller than in any of the 
former species, about 7 mm, although it sometimes reaches 10 mm; its 
shape is spherical pyriform. Its color is white, often turning greyish 
in the course of days. The cover is thin with threads of about 8 mic- 
rons in diameter, forming a very tight tissue of smooth surface, with 
a paper texture, and completely lacking exterior ornaments (Fig. 2). 
The egg-sac is fairly resistant to finger pressure. 
The egg-sac of L. geometrious . many times figured, is very charac- 
teristic: its color is whitish when just formed, turning yellowish in the 
course of days. It is spherical; its size about 10 mm in diameter; it is 
covered with conic protuberances that give it the curious aspect of a 
war-mace (Fig. 1). 
We are thankful to Dr. Herbert W. Levi, for his generosity and 
advice on the publication of this note and to Emilio Clementi for 
taking the photographs. 
