ICHNEUMON-FLIES 557 



either all Hcmitehs or all Pesomaclnis. It is to be hoped that 

 this interesting case will be fully elucidated. 



Although the Ichneumonidae are perhaps the most purely 

 carnivorous of all the great families of Hymenoptera, there is 

 nevertheless reason for supposing that some of them can be 

 nourished with vegetable substances during a part at any rate of 

 the larval existence, Giraud and Cameron ^ having recorded observa- 

 tions that lead to the conclusion that some species of the genus 

 Pimpla may inhabit galls and live on the substance, or juices 

 thereof 



Over 1200 species of Ichneumonidae are known to inhabit 

 Britain, and there can be no doubt that this number will be 

 increased as a result of further observation. Unfortunately no 

 general work has yet been published on this department of our 

 fauna, and the literature is very scattered.^ The species of 

 North America have not received so much investigation as those 

 of Europe, and the Ichneumon fauna of the tropics remains almost 

 uninvestigated. Six sub-families are recognised : Agriotypides, 

 Ichneumonides, Cryptides, Tryphonides, Pimplides, Ophionides. 

 Of these the first is the most remarkable, as it consists of an 

 Insect having aquatic habits. It 

 has for long been known that the 

 unique species Agriotypus armatus, a 

 rare Insect in our islands, is in the 

 habit of going under water and re- 

 maining there for a considerable 

 period, and it has now been satis- 

 factorily ascertained that it does this 

 for the purpose of laying its eggs in 

 the larvae of Trichoptera.^ The re- 

 sultant larva lives inside the cases 



„ • o an n ■■ j-„ T(- FiG- 364. — Aqriotypus armatus, 



of species of Silo, Goera, etc. It ^^^^^^^^ ^^.^^/^^ (liter Curtis.) 



undergoes a sort of hypermetamor- 



phosis, as its shape before assuming the pupal condition 



1 i:nt. Month. Mag. xiii. 1877, p. 200. 



2 A catalogue, with references, of tlie British Ichneumonidae was published by 

 the Entomological Society of London in 1872. Since then many additional species 

 have been detected and recorded, by Mr. Bridgman and others, in the Transactions 

 of the same Society. 



3 Klapalek, JEnt. Month. Mag. xxv. 1889, p. 339, and Arch. LandescHrchforschung 

 JBohmen, viii. No. 6, 1893, p. 53. 



