CHAPTER XX. 
Order SlPHONAPTERA (Siph-o-nap'te-ra). 
The Fleas . 
The members of this order are practically wingless , the 
wings being represented only by minute scaly plates . The 
mouth-parts are formed for sucking . The metamorphosis is 
complete . 
These tiny tormentors are best known to us in the adult 
state ; for it is only during this period that they annoy us 
and our household pets. The larvae and pupae are rarely 
observed except by students who search for them. 
The name of the order is from two Greek words : siphon , 
a tube ; and apteros , wingless. It refers to the form of the 
mouth and to the wingless condition of the insects. 
In our more common fleas the body of the adult is oval 
and greatly compressed, which allows the insect to glide 
through the narrow spaces between the hairs of its host. 
The integument is smooth, quite hard, and naked, except 
that there are many strong spines, 
which are arranged with great 
regularity (Fig. 598), and thus af¬ 
ford good characters for distin¬ 
guishing the different species. 
The smoothness and firmness of 
the body makes it easy for the 
insect to escape when caught be- 
Fig. 598. The Dog-flea and its larva. tween the fingers of man or the 
teeth of lower animals. Doubtless the backward projecting 
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