372 ARANEIDEA. 
only. The web of the true Theridion consists of a tangled mass of crossing threads, in 
the middle of which the spider hangs head downwards, while the egg-cocoon—some- 
times one, sometimes three or more, circular or pear-shaped—is concealed within a 
neighbouring leaf, or hangs in the toil itself, as in Steatoda tepidariorum, Latrodectus, 
&c. One very distinct group of these spiders may be recognized by the possession in 
the male sex of a stridulating-organ, formed by the toothed and chitinous margin of 
the cavity on the anterior portion of the abdomen rubbing against the convex granulate 
surface of the posterior portion of the carapace (Asagena, Teutana, Lithyphantes, 
Coleosoma, &c.). Another group (Latrodectus) is remarkable for the evil reputation, 
which its members have long enjoyed, of being able to inflict a most dangerously 
poisonous bite. Although there is abundant testimony of serious consequences from 
the bite or sting of some insect or spider living in the places where Latrodectus is 
found, there is still great need of direct evidence as to the actual culprit. The spiders 
themselves are very handsome, with their jet-black bodies slashed and spotted with 
vermilion. 
One of the more interesting members of the family (Anelosimus socialis) passes its 
life, not in the semi-solitary condition which prevails amongst the majority, but in a 
community consisting of many hundreds. The communal snare in this case is often 
immense, covering bushes and shrubs to the height of ten or twelve feet and often a 
yard or more in width. Perhaps the most beautiful of all the Theridiide are, however, 
those belonging to the genus Argyrodes ; they are mostly very small, but their bodies 
are spangled with brilliant silver, so that when hanging in the webs of the larger 
Argyopide (Nephila &c.} they shine like drops of water in the sunlight, a resemblance 
which doubtless serves them as a protection against their enemies. Allied to these are 
the curious forms belonging to the genus Ariamnes, which have the abdomen prolonged 
into a worm-like appendage; this, as I have myself observed in Brazil, is wriggled to 
and fro, looking like a small caterpillar. But of what service to the spider this 
accomplishment may be is not easy to guess; for on the one hand it seems likely to 
attract the attention of grub-eating wasps and ants, though on the other it may attract, 
within striking distance, gnats and small flies who become curious to ascertain what 
the wriggling phenomenon may portend. | 
The various genera into which the members of the family are divided may be 
recognized by the following characters, though it cannot be declared that in all cases 
they are satisfactory :— 
| GENERA. 
i. Males with a stridulating-cavity on the abdomen, its chitinous 
margin toothed ; (colulus present). 
A. Chitinous margin of stridulating-cavity continuous, not bifid. 
~* Sternum prolonged between coxe iv., forming a setigerous 
chitinous piece. 
