68 THE PROBLEM OF HORSE SICKNESS. 



Pxrctoplionts aiireosqiiam\(j("y, CcUia squamosa, Alycorliyiic/nis 

 manritiaiins, GrabJiamia caballa, Ciilex ondcrstcpoortcnsis, 

 Nyssorhxiichiis prctoriensis, Stcmgoniyia argentcopiinctata, 

 N\.':orh\nchns prctoriensis, var. ritfipcs, PyrctopJioriis costal is, 

 MyzomyJ.a fnnesta. 



Some of these species were represented by only a few 

 numbers, whilst others were numerous. The sum total so 

 collected and let loose amounted to 461 individuals. In no 

 instance was the disease transmitted. 



The second series of experiments were carried out with 

 the engorged mosquitoes collected in boxes wdiich contained horses 

 suffering from horse-sickness. They were then liberated in an 

 insect-proof box containing a suscejjtible horse. 



1. Of an imdescribed Cidicoidcs sjjecies were liljerated in 

 two boxes — in the first, a total number of 144 females from the 

 22nd March to 29th March, 1915; in the second one, 150 females 

 between the 26th March and 31st March, 1915. 



2. My::orhyncluts maiiritiamis: 31 engorged females were 

 liberated between 17th March to 17th April, 191 5. 



3. Myssorhyiiclius prctoriensis: 25 engorged females were 

 liberated between 15th March to 14th A])ril. 191 5. 



4. A^y::orrhyncliiis prctoriensis. xiir. ritfipcs: 10 females were 

 liberated between 27th March to 6th April, 1915. 



5. Cellia squamosa : 42 engorged females were liberated 

 from 15th March to 14th April, 191 5. 



6. Pyrctophorus aureosquamigcr: 3 engorged females were 

 liberated from 31st March to Sth A])ril, 191 5. 



7. Banksinella luteolateralis: 6 engorged females were 

 liberated from 23rd March to 2nd April, 191 5. 



8. Pyrctophorus costalis: 4 engorged females were liberated 

 on 31st March, 1915. 



In the third series of experiments the mosquitoes, caught 

 engorged in traps containing a horse suffering from horse- 

 sickness, were kept in wide glass cylinders closed on both ends 

 with muslin. These cylinders were pressed against the skin 

 of the suceptible horse, when the mosquitoes would sometimes 

 feed. The mosquitoes were fed on siisceptible horses at intervals 

 of two to five days. The following species were selected, being 

 the most commonly found: — Pyrctophorus costalis, Cellia 

 squamosa, Myzorhynclius mauritianus, and Culex transz'aalensis. 



These experiments were all under the care of Mr. Bedford, 

 the Entomologist of the Division. 



It is regrettable that all efforts were negative. They can, 

 however, not be interpreted as showing that the species concerned 

 do not transmit the disease. The failures are, in our o|Mnion, 

 due to a number of circumstances — z'ic, the dilffcultv of keeping 

 mosquitoes alive in an insect-proof loose-box together with a 

 horse for a sufiiciently long time, or even in a glass cylinder 

 when feeding them individually. It is true some mosquitoes did 

 live in captivity, but it must be remembered, in analogy to 



