GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 25 



possessed a normal longevity as compared with others in rearing 

 experiments. 



The above percentage of mortality is based upon those experiments 

 in which the fungus occurred. As there seems to be no reason for 

 attributing the fungus to soil or media it is well to base this per- 

 centage upon all experiments in tin boxes and where pupa3 were in 

 close proximity. In Tables II and VI, 630 larvae produced 578 pupae. 

 Of these 247, or approximately 43 per cent, developed a fungus. Of 

 the ones kept under observation 57 per cent emerged, so that only 43 

 per cent of the infected pupae were rendered inviable; 43 per cent 

 of 43 per cent would approximate 18.5 per cent, or the percentage of 

 loss in rearing experiments where numbers were kept in close prox- 

 imity, which probably allowed the infection to spread over indi- 

 vidual lots. 



In Table III it is shown that no infected pupae were found, and 

 should a fungus develop in such conditions the single location of 

 pupae would prevent its spreading. This fungus has never been ob- 

 served upon normal G. intestinalis or G. nasalis, though with dead 

 larvae of any Gastrophilus a long growth of fungus quite different 

 from that met upon living G. haemorrlioidalis pupae is frequently 

 found. 



PEEDATOES AND PAEASITES. 



The dropping of larvae under varying conditions and in locations 

 where they do not pupate in close proximity renders the situation 

 such that very little could be expected of predators and parasites in 

 control. In rearing experiments some field mice devoured pupae 

 on grass sod, but even though they feed upon these in nature it 

 is not likely that a great many are devoured. Chickens probably do 

 not feed upon many larvae when they drop, though a single hen has 

 been known to devour about 40 dead G. intestinalis removed from a 

 horse by a carbon disulphid treatment, and without any noticeable ill 

 effects upon the chicken. 



Desiring to know if the widely distributed Nasonia brevicomis, 

 which parasitizes various species of dipterous pupae, could be reared 

 upon G. haemorrlioidalis pupae, repeated efforts were made, but with- 

 out success. The indications are that the flycatchers feed very little 

 upon Gastrophilus adults. On account of the danger in shooting 

 such birds in pastures very few examinations of stomachs have been 

 made. 



LIFE-HISTORY NOTES. 



ADULT LONGEVITY. 



The life of adults appeared so short at the beginning of experi- 

 ments that it was attributed to abnormal conditions, but various cages 

 and environments did not materiallv increase the periods. A total of 



11216°— 18— Bull. 597 4 



