EARWIGS 



21 I 



individuals. There are seven pairs of abdominal spiracles, which, 

 however, are very minute, and can only be found by distending 

 the body as shown in Fig. 103. The ventral chain consists of 

 nine ganglia (the sub-oesophageal centre is not alluded to by 

 Dufour) ; the three thoracic are equidistant and rather small ; 

 the hindmost of the six abdominal ganglia is considerably larger 

 than any one of the other five. 



The ovaries of Labidura riparia and Forficula auricularia are 

 extremely different. In L. riparia there are on each side five 

 tubes, each terminating separately in an 

 obliquely directed lateral part of the 

 oviduct. In F. auricularia there is but 

 one tube on each side, but it is covered 

 by three longitudinal series of very short 

 sub-sessile, grape-like bodies, each of the 

 two tubes being much dilated behind the 

 point where these bodies cease. 



The testes in earwigs are peculiar and 

 simple ; they consist, on each side, of a 

 pair of curvate tubular bodies, connected 

 at their bases and prolonged outwards in 

 the form of an elongate, slender vas de- 

 ferens. The structures in the males of 

 several species have been described at 

 some length by Meinert, 1 who finds that 

 in some species a double ejaculatory duct 

 exists. 



The young is similar to the adult in A 

 form; in the winged forms it is always FlG _ in._"ovaries of LaU- 

 easy to distinguish the adult by the full dura riparia, A ; and For- 



. . ficula auncularia, B. 



development of the wings, but in the (After Dufour.) 

 wingless forms it can only be decided 



with certainty that a specimen is not adult by the softer and 

 weaker condition of the integuments. Scarcely anything appears 

 to be known as to the life -history, except a few observa- 

 tions that have been made on the common earwig ; Camerano 

 found 2 that this Insect has certainly three ecdyses, and possibly 

 at present chiefly one of nomenclature, we make use of the more usual mode of 

 expression. 



1 As on last page, and also op. cit. v. 1868, p. 278. 



- Bull. Etit. Ital. xii. 1880, p. 46. 



