CHAPTER XVI 



THE COCKROACH. INSECTS 



Common as they now are, cockroaches have only been 



introduced into England comparatively recently. 



Cockroaches. ~. » , . ° «_i_..rii--rr.. 



The first specimens were brought from the East 



by trading vessels at the beginning of the seventeenth century, 



and one hundred and fifty years later Gilbert White could 



still speak of the cockroach as "an unusual insect" at Sel- 



borne. This species was the Common Cockroach, Periplan- 



eta orientalis. More recently another species, P. americana, 



a native of tropical America, has been introduced and is 



spreading rapidly. Both are nocturnal insects which 



haunt human dwellings, hiding in corners and crevices 



by day. They seek warmth, as is natural in view of their 



origin, and devour any kind of food they can find. 



In its main lines the anatomy of a cockroach resembles 



that of a crayfish. The animal is segmented, 

 aOoekroacV t ^ e segments being unlike and grouped into 



three regions known as head, thorax, and 

 abdomen, but these do not correspond with the parts 

 similarly named in the crayfish. There is a thick cuticle, 

 and jointed limbs are found on the head and thorax. The 

 thorax bears also two pairs of wings. At the sides of the 

 head lie a pair of large, unstalked, compound eyes. The 

 ccelom, of which traces are found in development, dis- 

 appears in the adult, but there is a haemoccelic peri- 

 visceral cavity containing blood. 



The head is short and deep. Seen from in front it has 

 Head a P ear - sna P ed outline, with the narrow end 



downwards. Its armour consists of several 

 pieces — two epicranial plates side by side above, two gence 

 at the sides below the eyes, and a clypeus in front. A labrum 



