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 INSECTS emerge to form a cocoon or remain in the pupa-case of their victim to await their final transforma- tion. In the case of the larger ichneumons only a single egg is deposited in each larva attacked, but with the smaller forms the number may be considerable. Bignell, for instance, has hatched 1 80 braconids out of a single larva of Arctia ca/a, and I2OO Microgaster have been bred out of another Lepidopterous caterpillar. Though a few ichneumons are apparently limited to a single host, the majority have a fairly extended choice. Morley mentions that the common Cryptid, Hemiteles areator, has been bred from eighteen different Lepidoptera, including Bombyces, Tortrices, and Tinea ! Lepidoptera are the best known, but by no means the only victims. Many of the Tryphoninae are parasitic on saw-fly larvae, though the Schizodontes for the most part affect Diptera. The Pimplinae prey largely on the larvae of Coleoptera and Aculeate Hymenoptera, and several of the species attack spiders. An entire section of the Braconids, the Aphidiidae, devote themselves exclusively to Aphides, and a large number of still smaller forms finds sufficient material for the growth and development of one or more individuals inside the egg of another insect. Just as there are insects that prey upon insects, so there are parasites that prey on parasites. These hyperparasites are very numerous, and act as an effective check on the too rapid increase of the parasitic ichneumons and the consequent excessive destruction of lepidopterous and other phytophagous larvae. In such species the parent insect lays her egg in the body of a parasitic larva already ensconced within a vegetable-feeding caterpillar, and this egg develops and attains maturity at the ultimate expense of the two enclosing hosts. The extensive Ophionid genus Mesochorus is entirely composed of hyperparasites, and they are well represented in many other groups. Ichneumons as a rule are extraordinarily agile in their movements and swift and sudden in their flight. During the summer they are abundant almost everywhere throughout the county, and are often taken in considerable numbers at expanding foliage in spring. Many species are fond of plant honey, and may be taken in quantity at nectar-producing flowers. -As in the case of the saw-flies, umbelliferae generally possess a powerful attraction for ichneumons, and clumps of angelica, hogweed, and rough chervil are excellent collecting stations when the weather is bright. The only published list of Cornish Entomophaga is one of 125 species by Mr. E. D. Marquand in a paper ' The Ichneumonidae of the Land's End District ' in vol. i (new series) of the Transactions of the Penzance Natural History and Antiquarian Society (1880 4). In his 'Fauna of Plymouth; Ichneumonidae,' in the Transactions of the Plymouth Institute, 1 88 1 6, Mr. G. C. Bignell includes some Cornish captures, and there are many references to records from the county in Mr. C. E. Morley's recently-published British Ichneumons. Most of the species on the accompanying list have been taken, and a few bred by the students at the County Technical Schools, Truro, where on account of its supreme importance to agriculture and horticulture the sub-order is being made a subject of special study. The diffuse character of the literature on British Ichneumons and their allies has made the work of identification very difficult, and the fragmentary character of many parts of the accompanying list is due far more to this cause than to the lack of material. Several of the sections have not so far been studied at all. As no dubious species has been allowed on the list these sections are not represented. The writer wishes to acknowledge his indebtedness to Mr. G. C. Bignell for genial assistance so kindly given, and also to the late Rev. T. A. Marshall of Botus-Fleming, by whom it had been fondly hoped this article would have been written. ICHNEUMONIDAE LISTRODROMIDES JOPPIDES (continued) ICHNEUMONIDES Listrodromus, Wesm. Protichneumon fuscipennis, Wesm. OXYPYGINI nycthemerus, Grav. disparis, Poda. laminatorius, Fab. Stenichneumon, Thorns. TOPPIDFS Coelichneumon, Thorns. culpator, Schr. sugillatorius, Linn. pistorius, Grav. Hoplismenus, Grav. fuscipes, Gmel. trilineatus, Gmel. perniciosus, Grav. periscelis, Wesm. ochropis, Gmel. Automalus, Wesm. leucocerus, Grav. Cratichneumon, Thorns. alboguttatus, Grav. comitator, Linn. sicarius, Grav. Trogus, Panz. bilineatus, Grav. rufifrons, Grav. lutorius, Fab. consimilis, Wesm. nigritarius, Grav. exaltatorius, Panz. lineator, Fab. fabricator, Fab. Protichneumon, Thorns. ruficauda, Wesm. annulator, Fab. fusorius, Linn. castaneiventris, Grav. fugitivus, Grav. I 177 23