22 



BULLETIN" 597, IT. S. DEPARTMENT OF AGRICULTURE. 



Upon hard soil the larvae are seldom observed to move more than 

 a foot, and this sometimes requires 15 minutes. The tendency seems 

 to be confined almost wholly to burrowing, and it is only when 

 dropped on unsuitable places that they migrate. When exposed 

 upon hard, barren soil to the heat of the sun during the summer it- 

 seems certain that only a few find protection and eventually produce 

 adults. Certainly those not finding suitable protection from the sun's 

 heat die within a short time. On black loam at a mean temperature 

 of 122.9° F., 8 to 12 minute exposures caused 100 per cent mortality. 

 Yet some larva? seem to withstand even higher temperatures, for 

 adults were produced after having been exposed from 5 to IT minutes 

 at a mean of 129° F. Pupae, being unable to accommodate themselves 

 by moving for protection, seem to be very susceptible to heat. Ex- 

 posures of from 30 to 137 minutes at 116.6° F. were sufficient to 

 render them inviable. 



The heat generated in a manure pile produced greater mortality 

 upon larvae than ordinarily would be expected. Larvae buried with- 

 out protection at a mean temperature of 151.7° F. were dead within 

 15 minutes, having become soft and white. 



EFFECT OF SUBMERGENCE ON LARV^ AND FJJPJE. 



Although, as shown in Table III, excess moisture seems to have 

 had a destructive effect upon pupae, the effect of submergence upon 

 larvae is not so great. Larvae submerged 51 to 74 hours pupated and 

 produced adults. (See Table V.) Larvae submerged for 80 hours 

 pupated, but failed to emerge when kept under favorable breeding 

 conditions. While it is difficult to submerge pupae, as they float and 

 expose a portion of the posterior spiracles, three normal ones kept in 

 water for 5 days failed to emerge. In view of the results in Table 

 III, it is apparent that great mortality occurs among pupae during 

 wet seasons. 



Table V — Effect of submergence on larvce and pupce of Gastrophilus haemor- 

 rhoidalis at Aberdeen, S. Dak., 1915—16. 



Date 



Stage. 



Num- 

 ber. 



Period 

 submerged. 



Num- 

 ber 



pupat- 

 ed. 



Adults 



emerged, 



(male.) 



Larval 



lon- 

 gevity, 

 includ- 

 ing 

 period 

 of sub- 

 mer- 

 gence. 



Collec- 

 tion to 

 emer- 

 gence. 



Temperature after 



period of 



submergence. 



sub- 

 merged. 



Max. Min. Mean. 



1915. 

 Julv 5.. 



Larvae... 

 do.... 

 do.... 

 do.... 



Pupse... 



Larva? . . 

 do.... 

 do.... 

 do.... 

 do.... 



6 

 3 

 3 

 5 

 3 



9 

 5 



15 

 5 

 5 



51 hours 



4 

 2 



3 

 1 



Days. 

 5 



"17-26" 



9-14 



Days. 

 36 

 38 







85 41 63.'93 



July 14. . 



74 hours 



85 41 64. 21 



Do... 



20 days 





 

 







1 





85 41 

 80 40 

 82 40 



76 43 

 76 ! 43 

 96 ; 64 

 96 : 64 

 96 64 



62. 9i 



July 24. . 







58.14 



July 2.. 







59.40 



1916. 

 June 7.. 







12 



8-12 



8 



4 



7 



........ 



........ 



64.83 



Do... 



6 davs 





64.83 



July 12. . 







76.50 



80 hours 



5 





75.90 



Do... 







76.50 







1 





