GASTROPHILUS HAEMOEEHOIDALIS AND OTHER BOTS. 



17 



lowish, the larva contracting and assuming the form of a pupa. As 

 the puparium becomes more hardened a reddish tinge appears, but 

 after a few days it becomes black and retains this color until the 

 adult emerges. 



Table II. — Some environmental effects on metamorphosis of Gastrophilus 

 haemorrhoidalis at Aberdeen, S. Dak. 



Larvae 



Environment. 



Pre- 

 pupal 

 period. 



Pupal 

 period. 



Temperature, col- 

 lection to emer- 

 gence. 



Num- 

 ber 

 lar- 

 vae. 



Num- 

 ber 

 pu- 

 pae. 



Number 



adults 



emerged. 



Lon- 

 gevi- 

 ty 

 of 



collected 



from 

 rectum. 



Max. 



Min. 



Mean. 



larvse 

 not 

 pu- 

 pat- 

 ing. 



1915. 

 June 4 



Fresh horse manure in tin box 

 do 



Hours. 

 27-47 

 24-72 

 34-52 

 49 

 35-55 



53-146 



75-122 



122 



• 120 



50-144 

 27 

 18-47 

 23-39 

 19-26 



68 

 52-72 

 141-170 



Days. 

 39-45 

 46-54 

 37-44 

 38-40 

 36-48 



33-36 

 28-30 

 29-31 

 31-32 

 30-38 

 32-42 

 34-40 

 34-35 

 58-68 



41 

 36-40 

 34-35 



35 

 33-34 

 32-35 

 30-32 

 21-24 



° F. 

 88 

 88 

 88 

 88 

 88 



88 

 85 

 85 

 84 



84 

 84 

 84 

 85 

 88 



94 

 94 

 94 

 94 

 94 

 94 

 94 

 96 



° F. 

 35 

 35 

 35 

 35 

 35 



40 

 40 

 40 

 40 

 40 

 40 

 40 

 40 

 132 



42 

 42 

 42 

 42 

 42 

 42 

 42 

 48 



o R 

 63.21 



64.76 

 64.93 

 65.67 

 65.02 



65.73 

 62.40 

 62.56 

 62.89 

 64.33 

 63.23 

 62.06 

 64.23 

 60.59 



62.62 

 62.81 

 64.79 

 60.08 

 65.55 

 66.69 

 68.15 

 74.08 



14 

 33 

 16 

 7 

 12 



14 



10 



10 



7 



27 



34 



33 



8 



7 



5 

 5 

 2 

 1 

 11 

 17 

 28 

 46 



14 

 31 

 13 

 7 

 11 



14 

 10 



8 



6 



25 



30 



33 



5 



7 



4 



4 



2 



1 



8 



17 



25 



44 



10 



22 



8 



2 



9 



5 

 5 



7 

 4 



18 



26 



28 



2 



3 



4 

 3 

 1 



1 

 5 



16 

 20 



38 



Days. 

 4 





.do 



8 





do 











June 12 



Glass jar and fresh horse ma- 











Do 





15-22 



Do 





15 



June 14 

 June 18 

 June 17 

 July 12 



Aug. 7 



1916. 



May 22 

 May 23 

 May 30 

 May 31 



do 



do 



Moist manure in tin box 



Black loam in tin can 



16 

 12 







.do 



11 



...do 





...do 





...do 



42-96 

 75-100 

 44 



5 









June 10 

 June 23 



do 



Clean tin box and moist loam. 



4 



5 



1 Minimum, Sept. 21. 



In rearing larvae to adults a most convenient and efficient method 

 was utilized by placing them in clean tin salve boxes upon moist sand 

 in bread pans. Table II gives some results of rearing under such 

 conditions, using various media within the tin boxes. The period of 

 collections extends from June 1 to August 7, which includes prac- 

 tically the entire season during which larvae appear at the anus of 

 horses in Aberdeen, S. Dak. It will be observed that the prepupal 

 stage, the period from removal of larvae until pupation, varies from 

 18 to 170 hours. This is a much greater range of time than is normal 

 and may be attributed to the fact that larvae were removed before the 

 critical period of dropping. In some instances under varying con- 

 ditions they did not pupate, and, while some larvae died within a few 

 days, one is recorded as living for 22 days. 



The removal of larvae from the rectum prior to their normal ex- 

 posure to the air at the margin of the anus has a pronounced effect 

 upon rearing. A small percentage have been reared which were fully 

 11216°— 18— Bull. 597 3 



