147 



oaitle and dogs, llacmatohia st/mulans, Mg., and Lyperosia 

 'jrrltnns, L., feed ouh- on the blood of horned cattle, on whose 

 bodies thej- remain constantly, even while resting, showing, in 

 his opinion, the beginnings of a Avell defined parasitism. 



Distinctions are drawn between Musca doiiiestica and ,S'. cal- 

 i-ttrans as regards structure, attitudes and habits. The maximum 

 number of eggs found by the author in females of Stomoxys in 

 South Russia was IIG, whereas J/, doviestica lays i;c:U to 160 

 eggs which hatch in about half the time. Observations carried 

 out during a whole summer confirmed Newstead's conclusion that 

 S. raJcitrans does not oviposit in horse or cattle dung in open 

 fields and woods; and the same was found true of M. domestica. 

 P.ut in towns and around stables, etc., heaps of horse dung form 

 the chief, if not the only, breeding places of Stovioxys, which 

 however was never observed to breed in cattle dung in similar 

 situations. Details are given of experiments which show the 

 marked preference of the larvae for horse dung as compared 

 with cattle dung or human excrement. But S. caJcitnins is by 

 no means purely a dung-feeder, and the author cites records of 

 several other observers to the effect that it breeds in decaying- 

 vegetable nuitter, but does not mention having observed this in 

 Russia. In South Russia the whole development from egg to 

 imago occupied from 82 to 38 days ; the eQ;^; stage lasting 24 hours, 

 the larval stage 1-4 to 24 days, and the pupal stage 12 to IT days. 

 The larva and pupa are fully described, and the author expresses 

 the opinion that the figures of the spiracles given by Howard and 

 by Lahille are inaccurate. Among- the enemies of Stomo.rys 

 Dr. Portchinsky mentions insects of the genera McUinus and 

 Oxyheliis, as well as a C'halcid parasite. 



The author then proceeds to discuss at length the habits 0+' 

 various other Diptera which breed in dung, and points out that 

 their methods of reproduction form a regular series, first coming 

 those species which lay numerous small eggs, then those which 

 lay feAver large eggs, and finally every degree of larviparity. 

 He suggests that this form of viviparity has been developed 

 partly as a direct result of the keen competition for the food 

 supply, and partly because the dung does not normally remain 

 suitable as food for very long, owing to its rapid drying, especially 

 in warmer climates. This, he thinks, explains why the egg- 

 laying S. ealcitvuns and M. domestica, the larvae of wliich are 

 unusually voracious, do not oviposit on dung in fields and woods, 

 but have adapted themselves to the more favourable artificial 

 conditions which are supplied for them by man himself, and 

 which have the additional advantage of being- free from many 

 of the predaceous enemies, both dipterous and coleopterous, that 

 abound under more natural conditions. He also advances the 

 hypothesis that the tsetses ((rlos.sin(i) originally bred in dung 

 and have gradually dcA'eloped the habit of depositing a full-grown 

 larva owing to the difficulty of obtaining an adequate food supply. 



Formerly the Russian peasants used fringed coverlets (some of 

 which are described and figured) for protecting their horses from 

 Stomo.ry.s ; but of recent years they have taken to smearing the 

 animals with naphtha, or with fish liver oil, which is a very 

 efficient preventive. 



