ENEMIES OF APHIDES. 37 



reality by no means so sudden as is generally thought. The 

 observant student will recognise that they are merely stages in a 

 series of developments, often aberrant in a most remarkable 

 degree (as, for instance, in the case of Sitaris), but always pro- 

 gressive, and that the apparent arrest of the pupal stage is due to 

 the changes attending the development of the perfect insect within 

 the larva having become so extensive and so rapid that it would 

 be impossible for the functions of the latter to be continued fur- 

 ther. The conversion of the grub into the fly has commenced 

 long before the pupal stage is entered upon, and in many of the 

 orders the casting of the larval skin marks successive advances in 

 the development of structure which ultimately go to form the 

 perfect imago. A marked instance of this has already been given 

 in these pages in reference to the larva of Coccinella bipmictata, 

 Vol. IV., p. 292, and in the plate accompanying I have shown the 

 tarsus of the imago already perfected within the limb of the larva. 

 Indeed, in very many instances, the careful examination of a larva 

 when approaching its full growth will reveal much of the structure 

 of the imago well advanced within it. 



The larvae of the Orthoptera, as a whole, closely resemble 

 their parents in habit and also in anatomical structure, with the 

 e.\ception of the absence of wings. They frequent the same 

 surroundings, the organs of the mouth are the same, and their 

 nutriment is of a similar character throughout their existence. 

 To quote once again from Sir John Lubbock : — •" In the wingless 

 species of the Orthoptera there is little external difference, except- 

 ing in size, between the young larva and the perfect insect. The 

 growth is gradual, and there is nothing which would in ordinary 

 language be called a metamorphosis. In the majority of Orthop- 

 tera — though the presence of wings produces a marked difference 

 between the larva and the imago — the habits are nearly the same 

 throughout life, and consequently the action of external circum- 

 stances affects the larva in the same manner as it does the perfect 

 insect." 



But among the Dragon flies and their allies the larvae differ in 

 almost the widest possible sense from the imagines which spring 

 from them. Specially adapted for aquatic existence, provided 

 with branchial respiration and with swimming feet, the only 



