152 



The Philippine Journal of Science 



Distinguishing characters.— Screw-worm infestations are 

 usually secondary. The adults are attracted to open wounds 

 and blood, and the larvae enter the flesh through the broken skin. 

 In a few cases, crushed engorged ticks or drops of blood from 

 tick bites or horsefly bites are the attraction for the screw-worm 

 fly, and myiasis may occur at those points without previous 

 abrasion. Screw worms are often found in feet previously in- 

 jured by foot maggots. Foot maggots, on the other hand, usually 

 occur as primary pests. 



Screw-worm infestations may occur on any part of the body, 

 while foot maggots are apparently confined to the coronary 

 region of the tougher-skinned animals, and have been found as 

 high up the leg as the knee in the tenderer-skinned animals, such 

 as goats. Again, foot maggots appear to be confined to the 

 Artiodactyla, while screw worms attack all mammals. 



The larvae may be easily distinguished by the characters noted 

 in Table 3. 



SUMMARY 



The eggs of the foot maggot are laid on the hairs of the lower 

 extremities of the legs of the host animals. The larvae work 

 their way down to the skin and attempt to enter the flesh. In 

 the tougher-skinned animals, they are unable to enter at any 



