SOUTHERN CAETFORNIA ACADEMY OF ‘SCIENCES 7 
narily long grappling hooks, usually carried well back in a line 
with the head, are shot out—lke the toad’s toneue—much 
further than would ai first sight appear possible, and rarely 
iiss thelr aim. 
All the Arachnida, despite their preference (in many cases) 
for dry localities, must have water, or moisture in one form or 
another; and scorpions in particular are much more active after 
rain. 
The appearance of these groups is undeniably repellent ; and 
the remark is not seldom heard that, were a scorpion as big as 
an elephant, he would make existence impossible for all other 
forms of life. But most people either do not know, or else 
overlooks the fact that, whilst weight increases by cubes, 
streneth increases by squares only. So that, in conformity 
with this law, if a scorpion were as big as an elephant, he would 
be crushed by his own weight, and—consequently—would be 
powerless to harm! 
We may next consider the equipment of the Arachnida for 
defense. Their best protection hes m their powers of offense ; 
still, they possess various defensive artifices. To some, Nature 
has given an appearance which alone says, ‘“Hands off!’’ 
Others, like many insects, are protectively colored. Of such 
are some of the large oriental Mygalomorphex, or so-called bird- 
eating spiders. These, on rearing up on the hind lees in a 
posture of defense, display a striking band of pale yellow or 
red on the under side of the fore part of the abdomen, which 
may serve aS a danger-signal to warn off enemies. Others are 
imitative. Dr. MeCook deseribes an American spider which 
resembles the excreta of birds; and nearly all of the order can 
simulate death, and keep up the deceit for a considerable time. 
In the East Indies I have seen a very small black spider which 
lives in the nests of a specied of small black ant. These it re- 
sembles so closely, that only the minutest observation makes it 
possible to detect its real nature, which is revealed when the 
number of the legs is counted. So far as my observation goes, 
an example of true commensalism (or community of life) is 
here afforded, for ant and spider appear to live together in 
perfect amity, neither molesting the other. The trap-door 
spiders are, of course, protected by their tube, and by the diffi- 
eulty of detecting the trap-door, which usually exactly imitates 
the immediate surroundines. The common Californian Cteniza 
ean, moreover, keep her door shut from within, by anchoring 
her hind-lees to the lining of her tube, and by imserting the 
elaws of the forelegs into notches in the lid or door; in whielt 
position she ean offer a vigorous resistance to an intrusive 
knife-blade. 
