CH. Ill] THE COCKROACH 75 



folded. In arriving at the resting position two movements 

 take place. First the posterior portion of the extended 

 wing shuts up like a fan ; then the anterior part, which 

 remains flat and devoid of fan-like creases, moves back so 

 as to cover the posterior section. Both the anterior and 

 posterior free edges of the wing are now directed outwards 

 laterally, while the creased edge formed by the main fold- 

 ing is turned towards the mid dorsal-line. The anterior 

 firmer region of the wing lies uppermost so as to constitute 

 a protection to the more delicate hinder, and now under- 

 lying portion. All the folds run longitudinally. 



The legs are all built upon the same plan and are very 

 similar to one another, though the hindmost of the three 

 pairs is rather the largest. The form of the proximal joint 

 (coxa) is noteworthy; it is much flattened and can be 

 closely apposed to the ventral surface of the thorax, being 

 thus less prominent and less likely to impede the insect's 

 progress in narrow crevices. The flattened shape suggests 

 that it may be of further use as a shovel in scooping back 

 debris from beneath the body when the cockroach is 

 employed in scratching holes and enlarging small crevices. 

 Similar enlarged and flattened coxal joints are found in the 

 legs of many of the Fossorial Hymenoptera, e.g. Pompilidce, 

 which dig holes in the soil, and provision the nests thus 

 formed with spiders, flies, and other insects on which the 

 larvae feed. I have frequently observed these Pompilids 

 using their coxae in the manner just mentioned, and from 

 time to time backing out of the burrow with a heap of 

 loose sand dragged along by each pair of coxse, and kicked 



