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A disease due to the fungus, Empusa, is known to attack M. domestica 

 Tinder indoor conditions during the autumn. Two infected females of 



F. canicularis were found in a room on 15th and 23rd October, while a 

 number of C. erythrocephala in experimental cages were infected between 

 18th September and 12th November. Examples of H. denti'pes dead 

 of this disease were found out of doors on four occasions, the first being 

 on 30th August, i.e., before infection was observed among M. domestica. 

 Adults of M. domestica emerging from pupae kept under external 

 conditions and protected from contact with other large flies showed 

 the first signs of infection on 11th October. Between this date and 

 23rd October, 27 per cent, died of the disease, while a second period of 

 high mortality occurred between 8th and 16th November, when 43 per 

 cent. died. Contact with infected incli\dduals of the same species is 

 therefore not necessary to produce contamination. Infection must 

 have taken place (1) in the larval stage, before introduction into the 

 cages ; (2) through the agency of mites or very small insects ; or 

 (3) by spores carried by the wind. The growth of the fungus seemed 

 most rapid in warm, damp weather, but took place at a considerable 

 rate when the temperature was low, since a fly which showed the first 

 signs of infection on 16th November developed the characteristic bands 

 two days later. Two species of mites were frequently found attached 

 to various flies. Holotaspis sp., which occurred either singly or 

 several together on any part of M. domestica, 0. leucostoma, H. dentipes 

 and M. stabidans, remained attached for periods up to 192 hours, and 

 was apparently parasitic ; specimens of M. stabidans infected by this 

 mite were found as early as 26th April. A species of Gamasus, alhed to 



G. coleoptratorum, was abundant between August and October, and 

 plentiful also through the winter on animal matter upon which the 

 larvae were feeding. This species was generally found attached to 

 w^eak or dead flies, and in the latter case seemed to feed on the bodies. 

 Larval Nematodes were often attached to the legs of the mites, but 

 whether these are transmitted to the flies was not determined. Hypopial 

 nymphs belonging to the genus Tyroglyphus and adults of T. siro w^ere 

 found on some adults and in empty puparia respectively. These may 

 have served as food for Gamasus sp. Pseudo-scorpions belonging to 

 the order Chernetidea were common in 1915 ; Chelifer nodosus, Schr., was 

 found attached to the legs of M. domestica, M. autumnalis, 0. leucostoma, 

 and L. vaginalis during the summer and autumn and C. scorpioides 

 on Stomoxys calcitrans in October. The duration of the attachment 

 varied from one to four days. The puparia of various species were 

 found to be attacked by Braconid and Chalcid parasites. The 

 Braconids, Alysia manducator and Aphaereta cephcdotes, pass the winter 

 as larvae in the puparia of C. erythrocephala and other flies. From 

 puparia kept in the shade, blow-flies emerged between 23rd April and 

 nth May and specimens of A. manducator between 17th May and 

 16th June, and in much greater numbers between 19th September and 

 15th October. The first period of emergence coincided with the time 

 of oviposition of adults arising from overwintering pupae. Puparia 

 kept in the sun showed parasitism by Braconids and by Chalcids, 

 especially Melittohia acasta, AVlk. ; a Pteromalid was also present in 

 a few cases. M. acasta did not infest puparia kept in the shade, but 

 appeared in puparia transferred from the shade to a sunny position 

 on 29th April. Further observations pointed to the fact that 



