ii] GROWTH AND CHANGE 15 



both male and female carry a pair of jointed tail- 

 feelers or cercopods on the tenth abdominal segment, 

 and a pair of unjointed limbs or stylets on the ninth. 

 In the adult stage, both sexes possess cercopods, but 

 the males only have stylets, those of the female 

 disappearing at the final moult. 



Reviewing the main features of the life-story of 

 a grasshopper or cockroach, we notice that there is 

 no marked or sudden change of form. The fiewly- 

 hatched insect resembles generally its parent, except 

 that it has no wings. Wing-rudiments appear, how- 

 ever, in an early'instar as visible outgrowths on the 

 thoracic segments, and become larger after each moult. 

 All through its various stages the immature insect 

 nymph as it is called lives in the same kind of 

 situations and on the same kind of food as its parent, 

 and it is all along active and lively, undergoing no 

 resting period like the pupal stage in the transfor- 

 mation of the butterfly. 



One interesting and suggestive fact remains to 

 be mentioned. There are grasshoppers and cock- 

 roaches in which the changes are even less than 

 those just sketched, because the wings remain, even 

 in the adult, in a rudimentary state (as for example 

 in the female of the common kitchen cockroach, 

 Blatta orientalis, see fig. 4 a), or are never developed 

 at all. Such exceptional winglessness in members 

 of a winged family can only be explained by the 



