61 



Locusts and their Control. — Bull. Imp. Inst., London, xviii, no, 2. 

 April-June 1920, pp. 256-270. 



The biology of locusts in general is described, and the remedial 

 measures advocated against them in various countries are reviewed. 

 Several spray formulae for them are quoted, and their bacterial and 

 fungoid diseases are briefly discussed. 



Baer (W.). Die Taehinen als Schmarotzer der schadlichen Insekten. 

 Ihre Lebensweise, wirtsehaftliche Bedeutung und systematische 

 Kennzeichnung. ^Tachinids as Parasites of injurious Insects. 

 Their Life-History, Economic Importance, and Systematic 

 Characters.] — Zeitschr. angew. Entom., Berlin, vi, no. 2, February 

 1920, pp. 185-246, 63 figs. [Received 2nd December 1920.] 



The hosts of Tachinidae are not limited to Arthropods, for mammals, 

 birds, reptiles, etc., are parasitised by the Oestrinae, Calliphorinae, 

 and Sarcophaginae, but the chief sub-famihes, Tachininae, 

 Dexiinae, Rhinophorinae, and Phasiinae, confine themselves to 

 Arthropods, especially insects. No stage, and scarcely any large 

 group, is spared, and the most sheltered habitat, even under water, 

 affords no protection. In Central and Northern Europe there are 

 400-450 species of these flies parasitising insects. 



They appear early and disappear late in the j^ar, and are found 

 in the far North. Tachina larvaritm, L., occurs in Greenland, and 

 Peletieria aenea, Staeg., and Petina siylata, B.B., a parasite of Dasychha 

 groenlandica, Wck., are peculiar to that country. 



The adult Tachinids are chiefly found on flowers, in summer those of 

 Umbelliferae being the most attractive. They also feed on decomposing 

 matter, and live for a fairly long time. Examples of Ernestia rudis 

 found in August had apparently emerged in May, and in captivity 

 the female of HeUhosca nmscaria can h ve for 8 or 9 weeks. In favourable 

 weather mating takes place on the days immediately following 

 emergence. The male appears to be mature on leaving the cocoon, 

 but the female requires a further 2, 3, or more weeks to attain maturitj^ 

 a period that may be prolonged at low temperatures. A few species 

 of the genera Meigenia, Compsilitra and Lydella seem to mature in 

 3-4 days in sunny weather. 



Some species deposit their eggs within the host, and others in 

 proximity to it, on the food-plant. The latter eggs either hatch after 

 they have been inadvertently ingested, or the larvae remain fullv 

 developed in the shell until a suitable host touches them. The number 

 of eggs laid varies considerably. Eudoromyia magnicornis has furnished 

 a count of 3,200 eggs ; Shirmia sericana one of over 5,000, according 

 to Sasaki ; and Helicobosca muscaria, Mg., a minimum of 3. 



Descriptions are given of the method of penetration into the host, 

 the shape of the larva, the larva's three stages, and its hfe within the 

 host. The larvae may be divided into 3 groups according as to v hether 

 they remain in direct communication with atmospheric air, in secondar\' 

 (direct or indirect) communication, or become entirely cut off. The 

 larval period is usually short- — about 3 weeks for Parasetigena and as 

 little as 6 days for Meigenia floralis ; but this may be prolonged by a 

 resting or hibernation period in the host. For instance, Sturmia bima- 

 culata, parasitising the summer generation of Diprion {Lophyrus) pini, 

 matures in a few weeks. Some larvae of Sturmia, however, parasitise 

 examples of this sawfly that are entering the latent period, and such 

 larvae emerge in the following spring. 



