THE SCREW-WORM. 159 



distinct black stripes running from head to abdomen. When 

 leaving the pupa the fly is gray, but very soon it assumes 

 its glittering uniform, and the female is able to deposit her 

 eggs the second day after emerging. 



The above life-history does not vary from that of any 

 other flesh- or blow-fl3^ But the screw-w^orm attacks also 

 living man, dogs, sheep, cattle, horses, and even fowls, and 

 if it succeeds in forcing an entrance into the bod3' of such 

 hosts it causes the most excruciating pains, and not unfre- 

 quently death. Its points of attack are the sheaths of male 

 animals, the navels of new-bom stock, and any abrasion of 

 the skin. In man those suffering from a severe cold are most 

 apt to be attacked by these flies, which were formerly called 

 the "man-eating flies" {hominivorax) on account of their de- 

 vouring" man. In or near wounds found upon animals, or 

 in nostrils and other openings, they deposit their eggs which 

 immediately or very soon afterwards hatch. Theyoung and 

 active maggots force their way into the flesh, feeding and 

 growing as they go, and thus rapidly enlarge the sores. 

 They are soon out of sight and revel now in living flesh, un- 

 til the wounds enlarge to such an extent, if not discovered 

 and treated in time, that the infested animal has to die. If 

 siich maggots enter the nostrils of man in numbers they are 

 very apt to kill him unless steps are taken at once to remove 

 them. 



In regions where such flies are common great care should 

 be taken not to expose wounds and sores, as these flies have 

 been observed to deposit their eggs in them v^hile they were 

 being dressed. For the same reason persons should 

 never sleep out of doors, nor unprotected by mosquito bars, 

 wherever such flies abound. 



But it is not in the south alone that these flies occur. 

 We have them in our state as w^ell, though they have caused 

 but few injuries, being here in fact rather beneficial as sca- 

 vengers. Several cases are, however, on record, in which their 

 larvae have been found in the human ear.* In other cases 

 fowls suffering from cold were killed by these maggots; they 

 were eaten alive, so to speak. 



*Dr. Howard McI. Morton, of Minneapolis, reports two cases which he treated 

 3n 1895. 



