160 Mr. J. O. Westwood on the Eartvig. 



ing a pair of lateral triangular plates, which have the angles brought 

 into contact at the extremity of the body when at rest, but which 

 when opened form the anal passage : besides this the pair of large 

 terminal forceps and a small corneous central appendage are to be 

 noticed. 



On distending the abdomen of the female however, with a view 

 to the discovery of the two lost segments which exist in the male, 

 no trace can be observed of them from beneath, but from above 

 there are to be perceived at the base of the last, or as it appears 

 the 7th, abdominal segment two slight transverse impressions, 

 which, on being observed laterally, are found to terminate in two 

 ventral membranes. These therefore, it cannot be questioned, are 

 the traces of the two segments (the 7th and 8th), which in the males 

 are as fully developed as any of the others ; but the situation of the 

 spiracles or breathing pores most fully confirm the opinion. 



M. Leon Dufour, in his ' Recherches Anatomiques sur les Labidoures 

 ou Perce-oreilles,' published in the Annales des Sciences Natnrelles 

 for April 1828, has observed in his chapter upon the respiratory 

 apparatus that the spiracles of the Labidoura (which term he pro- 

 posed for the order of the earwigs) are extremely difficult to be ob- 

 served, on account of their extreme minuteness, and because they 

 are entirely hidden, either behind the scapular plates of the protho- 

 rax or the imbricated portion of the abdominal segments ; in fact, in 

 the ordinary state of the insect no one of them is to be observed. 

 M. Dufour however only notices the prothoracic and the abdominal 

 spiracles. Those of the mesothorax and metathorax which I 

 have discovered he has overlooked, and the number of the abdominal 

 spiracles he has not given. 



The prothoracic spiracles are placed, as M. Dufour has described, 

 beneath the epimera of the prothorax, in fact between the base of 

 the first pair of legs and the posterior angles of the dorsum of the 

 prothorax, being hidden from view by the free posterior margin of 

 the epimera. 



The mesothoracic spiracles are placed in a similar situation be- 

 tween the base of the legs and the posterior part of the place of in- 

 sertion of the tegmina, hidden as in the former pair by the epimera 

 mesothoracica ; but the metathoracic pair of spiracles are very 

 diiferently situated, being in fact dorsal, and placed near the 

 posterior angles of the mesothorax, but concealed from view by the 

 produced internal angle of the lower wings. 



Not content however with discovering externally the four minute 

 oval organs, which although having the appearance of spiracles 

 might not be such in reality, I dissected the several portions of the 



