22 INSECTS AND MAN 



division is mankind, in the latter the insects. The Inverte- 

 brates are still further divided into a number of groups 

 or phyla; the members of one phylum being known as 

 Arthropods, that is to say, animals whose bodies, enclosed 

 in a firm cuticle or exoskeleton, are composed of a series 

 of segments or rings, and whose appendages are jointed. 

 In all Arthropods, some of the anterior segments are fused 

 to form the head, and in some members of the phylum 

 the segments, posterior to the head, are fused to form 

 the thorax. The appendages comprise the legs, mouth 

 parts, and sensory organs antennae or " feelers." It is un- 

 necessary in a book of this nature to enter into anatomical 

 details, and the reader who desires to further his knowledge 

 in this direction is referred to one of the general text- 

 books of entomology mentioned in the bibliography. It is 

 sufficient for present purposes to notice that the Arthropods 

 are further subdivided into classes, namely, the Crustacea, 

 comprising crabs, lobsters, etc. ; the Myriapoda, comprising 

 centipedes, etc. ; the Arachnoidea, still further subdivided 

 into (a) Araneida spiders, and (6) Acarina mites and 

 ticks, and the Hexapoda or Insecta, true insects. 



The ensuing pages deal, for the most part, with the true 

 insects, that is to say, animals usually terrestrial or aerial, 

 with bodies, in the adults, divided into three distinct parts, 

 head, thorax, and abdomen, provided also with a pair of 

 antennae, three pairs of legs, and, as a rule, two pairs of 

 wings. Many important diseases of man and beast, how- 

 ever, have been definitely proved to be carried by ticks, and 

 the mites are not without interest in their relations with 

 man, so they have been included, although, strictly speaking, 

 they do not come within the scope of this book. The ticks 

 and mites may be distinguished from the true insects by the 

 fact that they have a fused head and thorax cephalothorax, 

 no antennae, and, when adult, four pairs of legs. 



Insects with similar general characters are arranged in 

 orders as follows : 



