[Illustration: FIG. 256. Web of young Theridium tepidariorum in a corner
of a trellis. A little less than the real size. The spider stood in the
close part near the middle.]
The Theridiums are small soft-bodied spiders, making large and loose
webs without any large flat sheet of silk, but only a slightly closer
portion where the spider stands, or a nest or tent connected with the
web. _Theridium tepidariorum_ (fig. 258) and _rupicola_ (fig. 261) live
in houses or among rocks, making large loose webs, in which the spider
often stands without any covering. They have the abdomen high in front
and tapering a little toward the spinnerets. _Theridium globosum_ (fig.
262) has the abdomen of the same shape. The other species are all small
and have the abdomen round and brightly colored. They live in more open
places on plants, where they make nests in which they are partly hidden,
and carry their webs over the neighboring leaves and twigs (figs. 253,
254).
[Illustration: FIG. 257. Web of young Theridium tepidariorum in a crack
of a rock. Half the real size. The spider stood in the middle under the
closely woven part.]
$Theridium tepidariorum.$--This is one of the most common house spiders,
and is often found in its webs among rocks, but seldom on plants. The
females (fig. 258) measure sometimes over a quarter of an inch in
length, but may mature much smaller. The legs of the first pair are
nearly three times the length of the body. The male (fig. 259) is
shorter and has longer legs. The color varies from dirty white to almost
black. The cephalothorax is yellow brown, and the legs light yellow,
with brown or gray rings at the ends and the middle of the joints. In
the males the legs are orange brown, darker at the ends of the joints.
The abdomen is high in front and narrows toward the spinnerets. In dark
and well-marked specimens the abdomen has, on the hinder part, six
transverse black marks curved upward, thicker in the middle, and partly
connected by black spots at the ends (fig. 260). These marks are most
sharply defined on the hinder edge, where they are bordered by silver
white. The upper mark often forms a conspicuous black and white spot in
the center of the abdomen. In light individuals all the markings are
smaller and less definite.
[Illustration: FIGS. 258, 259, 260. Theridium tepidariorum.--258,
female. 259, male. 260, abdomen of female seen from behind.]
It makes a large web in the corners of rooms, under furniture, and in
the angles of fences and between stones (fig. 255). It usually stands in
the most sheltered part of the web, where a part of it is more closely
woven than the rest, but not enough so to conceal the spider. It
occasionally makes the web in an open place where there is no shelter
above, and then it sometimes carries a piece of leaf into the web and
hides under it, as is the usual habit with some allied species. The webs
of the young are usually more regular in form than those of adults
(figs. 256, 257). A male and female often occupy the same web for a long
time. The eggs are laid in brownish pear-shaped cocoons, several of
which are made in the same season by one spider and hang in the web.
This species is found all over the world.
[Illustration: FIG. 261. Theridium rupicola, enlarged eight times.]
$Theridium rupicola.$--This resembles closely _tepidariorum_ and is
easily mistaken for the young of that species. It does not grow larger
than an eighth of an inch long. The colors are like _tepidariorum_,
usually dark gray with black spots, the back of the abdomen sometimes
almost white. The legs are distinctly ringed with light and dark. In the
middle of the abdomen is a pointed hump, the front part generally black
and the hinder part white (fig. 261).
It lives under stones and among rocks, in webs like those of
_tepidariorum_, often containing grains of sand which look as if placed
there by the spider, as sand falling into such a web would go through
without sticking to the threads.
[Illustration: FIG. 262. Theridium globosum, enlarged eight times.]
$Theridium globosum.$--This is another species with a high abdomen like
_tepidariorum_. It is about a twelfth of an inch long and almost as high
(fig. 262). The abdomen is a little flattened behind and pointed toward
the spinnerets. The hinder part is white, with a large black spot in the
middle, below which is sometimes a smaller black spot. Sometimes there
is a bright white line around the light area. The front upper part of
the abdomen is yellowish gray, and the under part brown. The
cephalothorax is orange brown, except a black spot between the eyes. The
legs are orange brown.
[Illustration: FIG. 263. Web of Theridium differens in the top of a
young pine tree. Half the real size.]
[Illustration: FIGS. 264, 265, 266. Theridium differens.--264, female
enlarged eight times. 265, male enlarged eight times. 266, end of palpus
of male.]
$Theridium differens.$--Female about one-eighth of an inch long, and the
male smaller. The abdomen is round, and the middle stripe often very
brightly colored, with white or yellow at the edges and red in the
middle (fig. 264). The rest of the abdomen is reddish brown, darkest
next to the white edge of the stripe. There are no distinct marks on the
under side. In males the stripe on the abdomen is obscure, and the whole
abdomen dark reddish brown (fig. 265). Sometimes, especially in young
spiders, the abdomen is entirely yellow, with indistinct brown markings.
The cephalothorax is orange brown, often darker in the middle, but with
no distinct stripe. The legs and palpi are yellow in females and orange
brown in males, slightly darker at the ends of the joints. The epigynum
has no openings in sight. They are on the inner side in the transverse
fold across the abdomen. The palpal organ (fig. 266) has two appendages
at the end, one hard and roughened and the other soft. The web is on low
plants of all kinds, usually two or three feet from the ground (fig.
263). There is sometimes a small tent, often hardly deep enough to cover
the spider, from which the web spreads two or three inches, according to
the shape of the plant. The cocoons of eggs are white and nearly as
large as the spider, and are attached in the nest.
[Illustration: FIGS. 267, 268, 269. Theridium murarium.--267, female
enlarged eight times. 268, end of palpus of male. 269, epigynum.]
$Theridium murarium.$--Length about one-eighth of an inch, with the
abdomen nearly spherical. The general color is gray. The legs are pale,
with dark bands at the end and middle of each joint. The cephalothorax
is pale, with a dark line in the middle and one on each side, the middle
line sometimes divided into two near the eyes (fig. 267). On the abdomen
there is an undulated middle stripe, white at the edges and the front
end, and reddish in the middle. On both sides of this stripe the abdomen
is nearly black and becomes gradually lighter toward the sides. The
sternum is pale, with a black edge and black stripe in the middle. The
under side of the abdomen is gray, with a long black spot in the middle
and a smaller one over the epigynum. There is little difference in size
or color between the sexes. The epigynum (fig. 269) has two round holes,
wide apart, near the thickened edge. The palpal organ (fig. 268) is
shorter and simpler than it is in _differens_.
[Illustration: FIGS. 270, 271, 272, 273. Theridium spirale.--270, male.
271, female. Both enlarged eight times. 272, end of palpus of male. 273,
epigynum.]
$Theridium spirale.$--This is a round-bodied spider of the same size as
_differens_ and _murarium_. The cephalothorax is orange brown above and
below, with an indistinct dark stripe as wide in front as the eyes and
narrowed behind. The abdomen has a middle stripe like _differens_,
nearly as wide in front as it is in the middle (fig. 271). The rest of
the abdomen is gray, darkest toward the stripe. The legs are pale,
sometimes with faint gray rings at the ends and middle of each joint.
The middle stripe of the abdomen is sometimes reddish as in _murarium_,
but oftener gray, with a dark spot near the front end. The males (fig.
270) have the same color and markings as the female and are sometimes
more distinctly marked. The male palpi (fig. 272) are very large, and
the palpal organ has a long tube coiled on the under and outer side. The
openings of the epigynum (fig. 273) are about their diameter apart.
[Illustration: FIG. 274. Theridium frondeum.--Varieties of marking,
enlarged four times.]
$Theridium frondeum.$--White, light yellow, or greenish white, with
black markings that are very variable (fig. 274). Usually the
cephalothorax has two fine black lines running back from the eyes and
uniting behind the dorsal groove, and black edges. The legs are usually
darkened with brown at the ends of the joints. The abdomen is large and
round, and has on the back a light undulated band bordered by brownish
translucent spaces, with two black spots just over the spinnerets.
Sometimes there are black spots in the translucent spaces, especially
toward the hinder end, and these may be united into two long black
stripes. In some individuals of either sex the black on the
cephalothorax forms a wide band in the middle, almost covering the back,
and a black stripe of similar width extends backwards on the abdomen for
half its length. These black-striped individuals have all the other
variations of color and markings. The males have all the colors and
spots brighter and the legs longer than the females. The mandibles of
the male are longer than those of the female and have at the base, in
front, a low conical point.
This species is found from the White Mountains to Alabama. In New
England it matures in July and is found on bushes all summer.
[Illustration: FIG. 275. Theridium unimaculatum, enlarged eight times.]
$Theridium unimaculatum.$--This little species differs in color and
markings from all the others, and may almost always be distinguished by
the white abdomen, with a black spot in the center of the back. The
females are a twelfth of an inch long and the males smaller. The
cephalothorax is orange yellow, with a black spot around the eyes,
extending back in a point as far as the dorsal groove, and there is also
a fine black line along the edges. The legs are orange, lighter in the
female and darker in the male, with the first and second pairs in the
male much stouter. The sternum is orange, with black edges. This spider
makes a web, like the other small species, among small leaves and
winters under dead leaves on the ground.