fin [March, 



Do House-flies hibernate ? — In my note to " The Times " (Sept. 10th, 1901), 

 suggested by extremely isolated cases of infectious illness in lonely country 

 cottages, I drew attention to the possible quite promiscuous spreading of 

 disease by insects. Yet, since then, no definite proof of this merely mechanical 

 conveyance of disease by insects, apart from their share in propagating infection, 

 through acting as hosts to other organisms, during certain phases of develop- 

 ment, has been forthcoming. 



We never know from what source light may come, and it is well for every 

 medical entomologist to inspect the fauna and flora of his patient's rooms. He 

 will conclude that, if the case is so strong against the house-fly, there is hardly 

 an insect Order that does not contribute a species to be, more or less, indicted with 

 it : Mallophaga (Docophorus, if birds are kept), Copeognatha (Troctes), Orthoptera 

 (Forficula, Blatta, Gnjllus), Anoplura (Phthirius and Pediculus), Thysanoptera 

 and Homoptera (Thrips and Aphis, if there are plants), Heteroptera (Cimex), 

 Coleoptera (Bermestes, Ptinus, Anobium, Xestobmm), Lepidoptera {Pyralis, 

 Aglossa, Acompsia, Endrosis, Tineola, Tinea), Biptera (Pollenia, Calliphora, 

 Culex), Aphaniptera (Pulex). Many of these insects have considerable powers 

 of locomotion, are hard to kill and have haunts of a kind to evade many means 

 of disinfection, while their habits are not, always, innocuous. Nor must we 

 forget other classes, e.g., Arachnida. 



Out-of-doors, such Biptera as Simulium, Ceratopogon, Anopheles, the Taban- 

 idse and Hippoboscidse are under suspicion, and it seems surprising that such 

 diseases as Anthrax are not spread even more disastrously than is the case. 

 But, if circumstantial evidence is strong against them and the house-fly, with 

 certain obvious exceptions there is little direct evidence. Bacteriological cul- 

 tivations of, e.g., tuberculosis bacilli from the feet, or proboscis, of any fly, 

 caught at random, has, as far as I know, not been effected. There is no obviously 

 increased incidence of possibly fly-borne disease at the season when the insects 

 are prevalent. An indiscriminate crusade is to be deprecated, or many benefi- 

 cent parasitic Tachinidse might come to grief. 



As regards the hibernation of the house-fly my evidence is negative. If 

 its size is small its numbers are large. Considering how freely hibernating 

 specimens of Vespa, Vanessa urticse, and Scoliopteryx libatrix are found in 

 houses, it is strange that, if this fly habitually hibernates, it should not be 

 more freely met with in this state. A few examples need not prove the rule. 

 I had my attention drawn to a hibernating colony of Eristalis tenax, in an 

 attic, some time ago. Of course the house-fly's hibernation may occur in 

 vegetable refuse, &c, in the open. Anyhow, the fresh air and sunlight of its 

 partly outdoor life must largely disinfect this member of Nature's great Sani- 

 tary Board ! I have never corroborated "Walker's assertion (Ins. Brit. Dipt., 

 vol. II, p. 110) concerning the allied Pollenia rudis, F. 



