PACKARD. — INHERITANCE OF ACQUIRED CHARACTERS. 357 



When about 6 mm. in length it moults a second time, and the full- 

 grown larva closely though superficially resembles a Crabro or Pem- 

 phredou larva, the small head being bent over forwards. By the 

 time it is ready to pupate it has wholly eaten the wasp larva, and the 

 temperature of the cell being high, a larva 5 mm. long grows large 

 enough in two days to fill the top of the cell of its host, and the larva 

 is ready to pupate about a week after hatching, so that its develop- 

 ment is very rapid. The beetles themselves do not live in the cells. 

 Chapman thinks they hibernate, and that the eggs are laid in the 

 spring or summer. 



We thus have in this insect three larval stages, the triungulin, and 

 two later stages, the great differences between the first and the last 

 two being apparently due to their parasitic mode of life, the larva 

 spending its second stage within its host, involving an existence in a 

 cell with a high temperature, an uninterrupted supply of rich, stimulat- 

 ing food, and a comparatively sedentary mode of life compared with 

 that of the triungulin at the beginning of its existence. It is quite 

 obvious that the hypermetamorphosis is primarily due to a great 

 change in its surroundings, i. e. the parasitic mode of life of the 

 beetle, habits of very rare occurrence iu the Coleoptera, numerous iu 

 species as they are. 



In the Proctotrypidae there is also a hypermetamorphosis.* 



In a species of Platygaster which is parasitic in the larva of Cecido- 

 myia, the first larva (Cyclops stage) is of a remarkable shape, not like 

 an insect, but rudely resembling a parasitic Copepod crustacean. In 

 this condition it clings to the inside of its host by means of its hook- 

 like jaws, moving about, as Gauiu says, like a Cestodes embryo with 

 its well known six hooks. In this stage it has no nervous, vascular, 

 or respiratory system, and the digestive canal is a blind one. 



After moulting the insect entirely changes its form, it is thick oval 

 cylindrical, nearly motionless, with no appendages, but with a digestive 

 canal aud a nervous and vascular system. 



After a second moult the third and last larval stage is attained, and 

 the insect is of the ordinary appearance of ichneumon larv;e. 



* Metschnikoff, Embryologische Studien an Insecten. Zeitsclirift fiir wis. 

 sens. Zoologie, XVI. 389-500, 1806. 



Ganin, Beitriige zur Erkenntniss der Entwickelungsgeschichte bei den In- 

 secten. Zeitsclirift fur wissens. Zoologie, XIX. 381-451, 1869. 



Ayers, On the Development of CEcanthus nivens and its Parasite, Teleas. 

 Memoirs Bost. Soc. Nat. Hist , III. 225-281, 1884. 



For an abstract of the work of Ganin, see Balfour's Comparative Embry 

 ology, I. 345-348; also Packard's Our Common Insects, 1873, pp. 161-107. 



