36 



THE COCKROACH : 



Head; Central Parts. 



The head of the Cockroach, as seen from the front, is pear- 

 shaped, having a semi-circular outline above, and narrowing 

 downwards. A side-view shows that the front and back are 

 flattish, while the top and sides are regularly rounded. In the 



Fig. 13. Front of Head. 



XlO. 



living animal the face is usually inclined downwards, but it can 

 be tilted till the lower end projects considerably forward. The 

 mouth, surrounded by gnathites or jaws, opens below. On the 

 hinder surface is the occipital foramen, by which the head com- 

 municates with the thorax. A rather long neck allows the 

 head to be retracted beneath the pronotum (first dorsal shield 

 of the thorax) or protruded beyond it. 



On the front of the head we observe the clypeus, which 

 occupies a large central tract, extending almost completely 

 across the widest part of the face. It is divided above by a 

 sharply bent suture from the two epicranial plates, which form 

 the top of the head as well as a great part of its back and sides. 

 The labrum hangs like a flap from its lower edge. A little 

 above the articulation of the labrum the width of the clypeus is 

 suddenly reduced, as if a squarish piece had been cut out of 

 each lower corner. In the re-entrant angle so formed, the 

 ginglymus, or anterior articulation of the mandible, is situated. 



The labrum is narrower than the clypeus, and of squarish 

 shape, the lower angles being rounded. It hangs downwards, 



