Introduction. xix 
distinct families : viz. Araneides, comprising all the spider? 
and spinners ; and Pedipalpi, comprising the tarantula and 
scorpions. 
Order II. Trachearim. These Arachnides are distinguished hy then 
respiratory organs, which consist of radiated or branched 
tracheae, receiving air by two circular openings. Their eyes 
vary from two to four. The principal animals belonging to 
this division are the long-legged spiders (Phalangium), and the 
mites (Acarus), including the gardener's pest, the little red spider 
(Acarus telarius), the cheese mite (Acarus Siro), and the harvest 
bug (Acarus or Leptus autumnalis). 
IV. The Insecta form the fourth and last class of articulated animals, 
and they derive their name from the Latin word insectum, which 
signifies " cut into," in allusion to the distinct divisions of head, 
thorax, and abdomen in the true insects: and in contradis- 
tinction to the Annelides, the bodies of which present no such 
divisions. The true insects are defined as animals without 
vertebrae, possessing six feet, with a distinct head furnished 
with antennae, and breathing through stigmatic openings, which 
lead to interior tracheae. The Myriapoda have, however, more 
feet. The following are the twelve orders into which this 
class is divided. 
Section I. Insects undergoing Metamorphosis. 
1. Coleoptera (from two Greek words signifying sheathed wings). 
These are the beetles, which are all furnished with membranous 
wings, with which they fly, and which are protected by horny 
upper wings, or wing-cases, called elytra. They are all masti- 
cators, and are all provided with mandibles or projecting jaws, 
and maxillae. 
2. Orthoptera, or straight-winged insects. This order comprises the 
crickets, grasshoppers, locusts, and similar insects. They have 
their upper wings of the consistence of parchment, and have 
mandibles and maxillae. 
3. Hemiptera, or half-winged insects, have frequently half the upper 
wing membranous, like the under ones, while the other half is 
leathery. To this division belong the bugs, the water-scorpions, 
the cicadae or froghoppers, and the aphides. These insects have 
neither mandibles nor maxillae, but in their place have a sheath 
and sucker. 
4. Neuroptera, or nerved-winged insects, such as the dragon-flies, have 
both pairs of wings membranous, naked, and finely reticulated. 
The mouth is adapted for mastication, and furnished with man- 
dibles and maxillae. 
5. Hymen:>pteru., membranous winged insects, such as bees, wasps, 
ichneumon flies, &c. All the four wings are membranous, but 
they have fewer nervures, and are not reticulated like those of 
the preceding order. The mouth is furnished with mandibles 
and maxillae, and the abdomen is terminated either by an ovi- 
positor or a sting. 
Lrpidoptera, or scaly-winged insects. These are the butterflies and 
moths, which are characterised by the farinaceous or scaly aspect 
of their wings, and the tubular or thread-like extension of the 
parts of the mouth. 
