258 
Hominoxious Arthropods 
ARACHN1DA 
In this class the antennae are apparently wanting, wings are never 
present, and the adults are usually provided with four pairs of legs. 
Scorpions, harvest-men, spiders, mites, etc. 
HEXAPODA (Insects) 
True insects have a single pair of antennae, which is rarely vestigial, 
and usually one or two pairs of wings in the adult stage. Familiar 
examples are cockroaches, crickets, grasshoppers, bugs, dragonflies, 
butterflies, moths, mosquitoes, flies, beetles, ants, bees and wasps. 
ORDERS OF THE ARACHNIDA 
a. Abdomen distinctly segmented. A group of orders including scorpions, 
(fig. 11), whip-scorpions (fig. 10), pseudo-scorpions, solpugids (fig. 12) 
harvest-men (daddy-long-legs or harvestmen), etc. Arthrogastra 
aa. Abdomen unsegmented, though sometimes with numerous annulations 
.SPHiEROGASTRA 
b. A constriction between cephalothorax and abdomen (fig. 7). True Spiders 
.Araneida 
bb. No deep constriction between these parts. 
c. Legs usually well developed, body more or less depressed (fig. 49). Mites 
. Acarina 
cc. Legs stumpy or absent, body more or less elongate or vermiform, or if 
shorter, the species is aquatic or semi-aquatic in habit, 
d. Four pairs of short legs; species inhabiting moss or water. Water- 
bears . Tardigrada 
dd. Two pairs of clasping organs near the mouth, instead of legs, in the 
adult; worm-like creatures parasitic within the nasal passages, 
lungs, etc. of mammals and reptiles (fig. 148). Tongue worms. 
.Linguatulina 
