GASTKOPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 



31 



and are swallowed. One author believes that a horse in eating will 

 rub the jaws upon the manger, which hatches the eggs, and that they 

 are taken into the mouth with the food. The fact that some eggs are 

 deposited upon the fore legs and portions accessible to the mouth 

 indicates that the ingress of larvae may be similar to that of G. intes- 

 tinalis. 



Longevity in this species seems to be increased over that of 

 G. haemo? i rhoidalis, as one reared adult kept under conditions similar 

 to those of the nose fly lived for 12 days. 



LARVA AND PUPA STAGES. 



Coincidentally with the appearance of G. haemorrhoidalis at the 

 anus of horses, the larvae of G. nasalis occasionally may be observed 

 to pass normally from horses and be found in their droppings. This 

 normally occurs when larvae become fully developed and is often 

 attributed by farmers to " a destructive effect of grass upon the bots." 



These larvae seldom migrate a great distance, and apparently only 

 burrow under the droppings for protection. Larvae which dropped 

 normally pupated in from 1J to 2 days, though the prepupal periods 

 in some cases in which larvae were removed in autopsies and cited in 

 Table VII extended for 7 days. It was observed that the short pupal 

 periods were preceded by long prepupal ones, and that larvae pupat- 

 ing within 2 days after dropping emerged in from 42 to 45 days. 

 At Victoria, Tex., Mr. J. D. Mitchell collected a larva under manure, 

 which pupated October 6, 1914, and emerged 20 days later. To 

 rear larvae collected in autopsies is a difficult task, even though they 

 are well developed and appear normal, but during the late summer 

 a small percentage may be reared if they are collected from horses 

 immediately after death. The larvae removed from dead animals 

 are capable of remaining alive and active for some time, some having 

 been kept as long as 25 days. Some larvae have been observed to 

 live submerged in water for 12 days. 



Table VII. — Pupal periods of Gastropliilus nasalis, Aberdeen, S. Dak., 1915-16. 



Lame 



Location. 



83 



> 



u 



a 



3 



Breeding environ- 

 ment. 



■d 



9 



a 



i 



c3 

 ft 



*d 

 *_ O 



o 



Number 

 emerged. 



8? . 



> M 



as 



II 



Temperatures. 



col- 

 lected. 



CD 



3 



6 

 B 







a 



03 



1915. 

 June 4 



Fresh dropping 



do 



Dropped from treat- 

 ment. 



1 



2 



4 



19 

 18 

 18 



With horse manure . 



Clean tin box; moist 



sand. 

 do 



1 

 2 



1 



3 

 3 

 3 



Days. 



42 



44-45 



31 



25-33 

 48 

 56 



1 



1 



1 



1 

 1 

 1 





Days. 



°F. 



88 



94 

 94 



98 



98 

 95 



°F. 

 35 



42 



42 



41 

 28 

 28 



°F. 

 65.30 



1916. 

 May 29 



June 12 



1 



2 

 ..... 



7 



3-15 



3-8 



11 



67.93 

 1 68. 98 



July 10 



Aug. 11 



11 



Dry paper in tin box. 



72.77 





60.26 





do 



59.97 











Horse treated with carbon disulphid. 



