128 ZOOLOGY. 
take flies, those formed by the large and handsome species of it (pl. 
TT, figs. 53, 59) are among the most regular. 
The cocoon in which the eggs of spiders are inclosed is carefully guar dod. 
Some species seat piceadel een over it as if in the act of incubation, some 
place it in their retreats, some in their webs, and the wandering species 
affix it to their abdomen. In this case, if it be forcibly removed, it is sought 
for with great solicitude, and when found, carried off or re-affixed. 
Flies and other insects constitute the chief food of spiders, and they must 
be taken living by the spider itself, or they will be generally rejected. Spiders 
are capable of fasting several months, and they pass the winter without 
food, being then torpid. They are eaten by various birds, reptiles, and _ 
other animals, and some of the stinging Hymenoptera fill the cells of their 
young with them for the food of the latter, being endowed with the remark- 
able instinct of disabling the spiders to such an extent as to render them 
perfectly helpless, so as to be unable to resist the young Hymenoptera, 
whilst they have life enough to keep them in a fresh state as long as they 
are wanted for food. 
The spiracles are situated near the base of the abdomen beneath, one or 
two upon each side of the middle. When there are but two spiracles, they 
communicate with extremely thin laminated gills which have their extremities 
directed towards the aperture, so that the air can be readily admitted to 
them. When there are four spiracles, the two posterior ones’ communicate 
with trachese. The latter belong to the family Mygalide (considered a 
section or sub-order by some authors, under the name of Zetrapneumones), ; 
and containing the sub-families Mygalinew, Atypinw, and Dysderine. 
Those with two spiracles have been named Dipneumones. They constitute 
the family Aveneidw, with the six sub-families: Avreneie, Theridionina, 
Epeirine, Thomisine, Lycosine, and Salticone. 
The species of Mygale (pl. TT, fig. 58) live in holes of their own con- 
struction, some of which are closed by a trap-door, which renders them 
difficult to find, and affords a protection to the ingenious constructor. The 
trap-door is wider externally than internally, or slightly conicai, and the 
mouth of the aperture is formed so as to receive it with great exactness, 
whilst the form is such as to prevent it from becoming fastened, as would 
often be the case were it cylindrical. This door is made of about thirty 
layers of silk and dirt, the layers being somewhat in the shape of small 
brass weights, the different sizes of which lie one within the other. Upon 
leaving or entering its burrow the lid closes after the spider by its own ~ 
weight, and when the animal is upon the outside it must be raised to allow 
it to enter. The elasticity of the hinge is sufficient to close the aperture if 
the lid be raised vertically, or drawn still further back; and it is assisted by 
the distribution of the earthy material, which is thickest towards the hinge, 
and on this account less likely to be thrown backwards beyond its centre of 
gravity. Near the margin of the inner side of the lid, and opposite the 
hinge, the Mygale forms a series of small holes to enable it to insert its 
claws and jaws to hold it in place, in case of an attempt to raise the lid from 
without; and if a knife is inserted so as to run beneath the spider, and the 
332 
