ADAPTATIONS TO HAUNTS AND SEASONS 269 



width of each segment seen in end view is often greater than 

 its depth, the ventral surface of the cuticle is, as a rule, 

 markedly convex, while the dorsal aspect is less convex or 

 flattened. Such a body-form is seen in earwigs, cock- 

 roaches and the great majority of beetles, which are adapted 

 for life on the ground and move principally by walking or 

 running. A relatively broad body is clearly best adapted 

 for this mode of progression ; the same general form is 

 also seen in many insects of comparatively feeble flight. In 

 insects of large size which live under stones or among leaves, 

 the dorso-ventral flattening is carried so far that the body 

 becomes very much wider than deep. This is apparent in 

 most cockroaches which live in the warm countries where 

 they abound in forests among fallen leaves or under bark. 

 In the familiar cockroaches which have been introduced 

 into our cooler regions, we notice that this flattened form 

 enables them to creep into warm shelters between the bricks 

 of stove or oven settings, and behind or beneath hot- water 

 pipes. In another household insect — smaller and more 

 unpleasant than the cockroaches — the blood-sucking " Bed- 

 bug," the flattening is carried to an extreme so great that 

 the breadth of the abdomen is twelve times as great as its 

 depth and the upper surface becomes concave. Here we 

 see a form of body suited to a creature that Hves as a parasite 

 closely adjacent to the skin surface of its host, and finds 

 shelter in the crevices of wooden furniture (Fig. 67, a, h). 

 It is suggestive, however, to remember that among insects 

 of the order (Hemiptera) to which the Bed-bug belongs, 

 a flattening of the body, similar if less extreme, is a common 

 feature. 



Among insects that are pre-eminently aerial in their 

 mode of hfe we notice an increase in the depth of the body 

 in proportion to its width. This is often particularly 

 evident in the thorax, where provision has to be made for 

 space and attachment for the powerful flight muscles, but 

 a deepening and relative narrowing of the abdomen may 

 often be noted. In many Hymenoptera and Diptera the 

 abdominal segments are distinctly broader than deep, but 



