ARTHROPODS. CLASS ARACHNIDA 135 
larger species, which measure five or six inches in length, 
may produce certain disorders chiefly affecting the circula- 
tion. In this country there are upward of thirty species, 
most of which are comparatively small. 
130. The harvestmen.—The harvestmen or daddy-long- 
legs are small-bodied, long-legged creatures which resemble 
in general appearance several of the spiders. They differ 
from them, however, in the possession of claws correspond- 
ing to the smaller ones of the scorpion, and in their method 
of respiration, which is similar to that of insects. During 
the day they conceal themselves in dark crevices or stride 
slowly about in shaded places; but at night they emerge 
into more open districts and capture small insects, from 
which they suck the juices. 
131. The spiders—The spiders are world-wide in their 
distribution, and are a highly interesting group, owing 
chiefly to their peculiar habits. Examining any of our 
familiar species, it will be seen that the united head and 
thorax are separated by a narrow stalk from the usually 
distended abdomen. To the under side of the former are 
attached four pairs of long legs, a pair of feelers, and the 
powerful jaws supplied with poison-sacs, while eight shin- 
ing eyes are borne on the top of the head. On the abdo- 
men, behind the last pair of legs, are small openings into 
the lung cavities which contain a number of vascular, leaf- 
like projections known as lung-books. In some species 
a well-marked system of trachee are also present. At the 
hinder end of the body are four or six little projections, 
the spinnerets, each of which is perforated with many 
holes. Through these the secretion from the glands be- 
neath is squeezed out in the form of excessively delicate 
threads, often several hundred in number, which harden on 
exposure to the air. According to the use for which these 
are intended, they may remain a tangled mass or become 
united into one firm thread ; and according to the habits 
of the animal, they may be used for enclosing their eggs, 
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