12 INTRODUCTION'. 



any of the other segments. In D. greeni, Burr, the cerci are 

 shorter, the increase in the number of segments is more gradual, 

 and the maximum number attained appears to be 18 or 20. 



Green was unable to count the exact number of ecdyses, but 

 observed four successive moults, the last revealing the perfect 

 insect. Each instar occupies about 10 days. In ecdysis, the skin 

 splits along the median dorsal line of the thorax and is shed 

 completely, even including the covering of the delicate caudal 

 appendages. The penultimate instar, or nymph, may be recognized 

 by the truncated cerci and also by the appearance of the 

 radiating pattern on the metathorax, showing in miniature 

 the future wing of the imago. The lateral glandular folds of the 

 abdomen appear when the larva is about half grown. 



A curious ])oint was also noticed by Green. In the penultimate 

 stage the anterior femora were broad and armed on the inner edge 

 with a row of spines, which gave them a distinctly raptorial 

 appearance : but he never saw them used for any purpose other 

 than locomotion. 



The segmented caudal cerci have been recorded, but not 

 described, in some unknown African species {vide Proc. Ent. Soc. 

 Washington, iv, nr. 2, p. 53, 1898). 



Terry (05) has described the egg and post-embryonic develop- 

 ment of CheJisoclies morio. There appear to be four larval instars 

 before the adult imago. Terry's observations on the manner of 

 increase of the antennal segments ai-e very interesting. It appears 

 that the larva has at first only 8 segments ; at the first ecdysis the 

 third segment is divided into four additional segments ; at the 

 second ecdysis, the third segment gives rise to four more; at the 

 third, to three more ; at the fourth, to one more, so that the normal 

 total of 20 is thus attained. 



Terry failed to discover any trace of segmentation in the 

 forceps of the embryo in ovo : this is interesting when compared 

 with Green's observations on Diplatys. 



Copulation. 



De Geer's description of the family life of the common English 

 earwig is generally known. According to this observer, the act 

 of copulation is effected by the male approaching the female 

 backwards, tapping her with his forceps, and then effecting the 

 connection tail to tail, the pair being thus arranged in a straight 

 line. Gadeau de Kerville has noticed and described the same 

 thing, and insists that, though the male seems to try to catch 

 hold of the female with his forceps, this organ does not appear to 

 be of any use either before or during the act. The male is 

 obliged to twist the apex of his abdomen so that the ventral 

 plates face upwards in contact with the ventral plates of the 

 female, and this torsion sometimes goes so far as to involve the 



