VIII, B, I Mitzmain: Stomoxys calcitrans Linnaeus 39 



domesticated animals. It is rarely found to annoy man to the 

 extent that prevails in temperate climates. Its attacks upon 

 man generally take place shortly after the atmosphere has been 

 cooled by a rain shower and at certain seasons of the year when 

 this species is unusually abundant. The following notes are 

 added to show the extent of the attacks of these flies on man 

 when they are abundant. 



At 8.50 a. m. August 27, 1912, a female Stomoxys calcitrans 

 flew into the laboratory after a rain shower, alighted on my 

 exposed arm, and in a few seconds commenced to scrape the skin 

 with its labellum. Within ten seconds sharp pain waS/ felt. 

 The probing continued for two minutes when apparently a 

 satisfactory insertion of the proboscis was effected. At this 

 time the distention of the abdomen of the fly became apparent. 

 The aspirating process caused only a dull pain. Although the 

 blood gushed into the stomach of the parasite the labium was 

 inserted to only one-third its length. The base of the labium 

 was not inserted nor was the labium buried in the skin to the 

 bulbous portion as is usual when this fly is feeding on other 

 mammals. 



The fly under observation fed for three minutes and thirty 

 seconds. A blood drop the size of a pinhead was left at the 

 site of feeding, and one hour later a very slight pain was felt, 

 while a minute haemorrhagic spot marked the place of feeding. 

 The bitten area on the arm was marked with a blue paraffin 

 pencil, and within an hour another fly settled within the bound- 

 aries of the blue mark. It fed one minute and a few seconds, 

 during which time a third fly appeared and made a bite only 

 4 millimeters distant from the blue mark, and fed for two 

 minutes. 



While I was jotting down these notes, another fly, the fourth 

 parasite, visited the bitten arm and selected a spot within the 

 marked area bitten by its fellows. All four of the foregoing 

 parasites were males. Less than ten minutes elapsed when a 

 fifth Stomoxys appeared on the bared arm, and commenced 

 operations within a centimeter of the area bitten by the last fly. 

 In this instance the parasite was a female, and, from appear- 

 ances, one which had been subjected to a long fast. This fly 

 required nearly two minutes to aspirate any blood. In six 

 minutes the labium was inserted to the maximum depth, that is, 

 to the bulb, and the fleshy portion of the labium leading into the 



