SKETCHES OF BRITISH INSECTS. 
CHAPTER I. 
INTRODUCTION. 
y\CLL Animals may be included in one or other of the 
following great Divisions or Sub-Kingdoms, as they 
are termed:—I. Vertebrata, II. Mollusca, 
III. Arthropoda, IV. Vermes, V. Echinodermata, 
VI. C(elenterata, VII. Protozoa. Insects, the sub¬ 
ject of the present volume, belong to the Sub-Kingdom 
Arthropoda, i.e., “having feet at the joints,” from 
upQpov “a joint,” and ttovq, t toSoq, “a foot;” the term 
implying that the animals are possessed of jointed ap¬ 
pendages articulated to the body . Not only insects, 
therefore, but the Myriapoda (centipedes), Arachnida 
(spiders, mites, scorpions), and Crustacea (lobsters, 
crabs, etc.,) belong to the Arthropoda, for in ail these 
four classes we find jointed appendages articulated to 
the body. The Aithropoda are again divisible into 
two large natural groups according to their mode of 
respiration. In the Crustacea the respiration is aquatic, 
in the three other classes it is aerial; in the former it 
is carried on by means of special organs called branchial , 
or where no such organs exist by means of the whole 
B 
