22.2 Woodworth and Ashcraft: Booponus intonsus 151 



in fields with plenty of wallows and the animals can soak them- 

 selves at will. 



HOST ANIMALS 



So far only Bovida? have been recorded as hosts. Maggot 

 specimens have been obtained from Hereford, Nellore, and Phil- 

 ippine cattle, carabaos, and goats. Data available are not suffi- 

 cient to allow the drawing of definite conclusions relative to the 

 susceptibility of the various kinds of animals. However, in the 

 vicinity of Los Bafios the order of percentage of attack observed 

 is : Hereford cattle, carabao, Philippine and Nellore cattle, goats. 



DIFFERENTIATION BETWEEN SCREW WORMS AND FOOT MAGGOTS 



The common screw worm of the Philippines, Compsomyia dux, 

 differs from the foot maggot in several very obvious details. 

 Because the former is the maggot most likely to be confused 

 with the foot maggot, descriptions of the larval and pupal stages 

 are included in this paper. 



COMPSOMYIA DUX ESCHSCHOLTZ 



Larva. — Body elongate, regularly tapering and wedge-shaped. 

 Posterior end truncate. Body yellowish white. Anterior 

 margin of each segment swollen and with several irregular rows 

 of short, stout, reclinate spines. Head bilobed, with a pair of 

 blunt tubercles, one above the other, on each lobe (Plate 3, fig. 

 2) . Oral hooks two, toothed, dark brown, and strongly recurved 

 ventrally (Plate 2, fig. 1). Segments 5 to 10 with lateral, spin- 

 ulose, fusiform areas against the anterior margin of the follow- 

 ing segment. Segments 6 to 11 with narrow, transverse, smooth, 

 fusiform areas on the somewhat broadened ventral part of the 

 swollen spinulose anterior rings. Amphipneustic. Anterior 

 spiracles probably not functional, indistinct, consisting of a row 

 of six small circular openings. Posterior stigmal plates approxi- 

 mate, situated at the bottom of a deep cavity at the posterior 

 tip of the body. Slits three, subparallel, without button, and 

 chitinous process not completely inclosing them. Ten small 

 tubercles on the edge of the stigmal cavity (Plate 5). Segment 

 12 with a swollen spinulose area ventrally which is bisected 

 transversely by a smooth area and gives rise to two, large, widely 

 separated tubercles. Length, 12 to 12.5 millimeters ; breadth, 3.5 

 to 4. 



Puparium. — Regularly ellipsoidal, chestnut brown to black. 

 Surface finely rugose, with recumbent spines located as in larva. 

 Anterior spiracles not apparent. Posterior stigmal plates not 

 sunken, but otherwise as in larva. Size variable. Average 

 length, 10 millimeters ; breadth, 3. 



