THE PROBLEM OF HOUSE SICKNESS. ^J 



mitted by the genus Plilcbotomiis. The exjierience that the 

 exclusion of winged insects from a stable excludes horse-sickness 

 must be regarded as a support of the theory- Experiments to 

 this effect were carried out many years ago. Onderstepoort 

 has been renowned for horse-sickness for many years ]Dast, and 

 this was the deciding factor in the selection of the place. The 

 laboratory has its stables so built that they can be made insect- 

 jDroof, and during the horse-sickness season, when the horses 

 are stabled, and no other iMxcautions were taken, no cases of 

 spontaneous horse-sickness ha\e occurred. Nevertheless, the 

 direct proof of transmission as it was forthcoming in the case 

 of malaria, or in the case of the tick-borne diseases, is lacking. 

 \\"e do not know which genus of insects has to be made respon- 

 sible. Persistent attempts to find this genus have been carried 

 out e^"er since we occupied the place in 1908. Blood-sucking 

 insects of nocturnal jjrevalence were trapped and collected. This 

 was done by means of so-called " mosquito traps," viz., small 

 houses with sufficient room to hold a horse, open to the access 

 of blood-sucking insects. A horse was placed in these houses 

 during the night, and next morning a collection was made of 

 the insects, principally blood-gorged mosquitoes, that were found 

 on the ceiling and walls. This collection was carried out 

 through a number of years, and it enabled us to find out which 

 mosquitoes were most prevalent during the horse-sickness season. 

 The collections were submitted to Professor Theobald, the 

 well-known authority on mosquitoes. He identified the species 

 and described the new ones. In the second rei)ort on the mos- 

 quitoes of the Transvaal, published in the second report of the 

 Director of \'eterinary Research, he enumerates the species 

 found in the Transvaal, a total number of 52. Of these, 46 

 species and some varieties were found at Onderstepoort, vh., of 

 the sub-family Anophaelinae : Genus — Myzomia, Pwotophorus, 

 Ccllia, Mycorhyiichiis, NyssorJiy)icliiis: of the sub-family Culli- 

 cina? : Genus — Mucidus, Stcgomyia. Sciifoinyia. Pseudo- 

 hozcardina, Tlieobaldia. Citlc.r, BankscncUa, Clirvsosonops, 

 Taciiiorhyticliiis, Psciidotcciiiorhyiichns ; of the sub - family 

 Uranotajninse : Genus — Uraiwfcriiia. Grahhaiiiia'; of the sub- 

 family .T^dinae : Genus — Mansonia. 



In the same traps were also caught other biting nematocerous 

 flies, viz., of the genus Culicoidcs. the si:)ecies Citliooides milnei 

 Austen, and of the genus Phleboiomns, an undescribed new 

 species, also a simulium of a new sj^ecies. 



The latest experiments undertaken wdth mosquitoes can be 

 grouped into three classes. 



The first series were carried out with the mosquitoes col- 

 lected in the trap-boxes in the season 1913-14 between the 3rd 

 December, 1913, and the 2nd May, 1914. They were released 

 in an insect-proof box, built for this purpose, and containing a 

 susceptible horse. 



The following species were used: — Culcx paUidopnnctata, 

 Culcx transvaalensis, Culcx tJicilcri, Banksenella luteolatcrolis. 



