498 MITZMAIN. 



droplet of freshly exuding blood, and among these often not an 

 individual belonged to a species with a piercing mouth; they 

 consisted principally of house flies. Other groups of flies sur- 

 rounding the Stomoxys attracted attention by the fact that 

 while it fed the rest waited. The latter gave evidence of great 

 impatience and eagerness in the movements of nudging one an- 

 other and colliding with the Stomoxys, apparently making efforts 

 to dislodge it. The Stomoxys having been satisfied, the other 

 flies pounced upon the feeding spot where a well-rounded blood- 

 drop trickled, and lapped the blood as it oozed from the wound. 

 In a moment the group disbanded with abdomens more or less 

 reddened and distended, the individual either flying off the host 

 to rest or joining another biting Stomoxys. In many instances 

 the Stomoxys was accompanied by a single fly which hovered 

 about it in a highly provoking fashion. Several minutes elapse, 

 however, before the Stomoxys is fully engorged and the blood 

 is left to the disposal of the secondary passive parasite. 



It has been noticed that even other bloodsucking flies found 

 on cattle often take advantage of the action of the more power- 

 ful proboscis of the Stomoxys. Lyperosia was found to await 

 its turn with other nonbiting flies for the free-for-all blood feast. 

 This was noted in two instances on the pachydermic skin of the 

 carabao where the relatively feeble mouth of this diminutive 

 muscid was a decided handicap. In this instance, especially 

 among grazing carabaos, Lyperosia will hover in a swarm above 

 a lone bloodsucking Stomoxys. To be sure the Lyperosia will 

 probe for blood on its ovm initiative, as will smaller flies like 

 some of the Chironomidse, but apparently when so much energy 

 is required on a thick-skinned animal like the carabao, blood in 

 the readily available form provided by the Stomoxys will be 

 imbibed readily. Lyperosia was never observed to provide blood 

 for other hawking dung flies, although this probably occurs. 

 Another haustellate muscid, a Philoematomyia, was observed to 

 feed independently of other flies. Although its mouth is not 

 strictly a piercing organ, the epidermis is penetrated, blood 

 being drawn to the surface of the skin and sucked cleanly. 



In order to secure additional evidence of the blood-feeding 

 habits of the nonbiting flies, experiments were conducted to de- 

 termine the relationship of the common house fly, Musca do- 

 mestica, to Stomoxys as a harborer and carrier of trypanosomes. 

 In these experiments it was aimed first to prove that M. domestica 

 can harbor within its body infective trypanosomes. The normal 

 protozoan fauna of these flies was not taken into consideration. 



