24 



BULLETIN 1218, U. S. DEPARTMENT OF AGRICULTURE. 



Egg Mass. 



The form of the egg mass of Tabanus phaenops varies in width 

 and length with the width or diameter of the object to which it is 

 attached. A mass attached to a flat piece of cork was 15.6 milli- 

 meters long and 5 millimeters wide. (PI. II, D.) The egg mass 

 tapers to very narrow ends. Specimens attached to slender stems 

 are longer and more narrow. The mass is constructed of two layers, 

 which are parallel to the object to which they are attached. The 

 eggs slant at an angle of about 30°. The mass when laid is white. 

 In a day or two it is dark gray, and before hatching is black. The 

 number of eggs in the masses hatched varied from 180 to 305, the 

 average being 290. The eggs are apparently not covered with cement 

 and become detached rather easily. 



Incubation Period. 



The egg of Tabanus ph-aenops measures 2 millimeters in length and 

 0.4 millimeter in width. The distal end, from which the larva 

 emerges, tapers to a narrow diameter. The opposite end is narrowed 

 on one side, giving the egg a rather flattened area where it is at- 

 tached. The incubation period is given in Table 4. 



Table 4. — Incubation period of Tabanus phaenops. 



Date. 



Egg mass No. 



Temperature. 



7661 



7662 



7666 



7668 



7673 



7677 



7692 



Max. 



Min. 



Mean. 



1918. 



0) 



C 1 ) 













86 

 84 

 82 

 79 

 83 

 86 

 85 

 86 

 88 

 89 

 93 

 93 

 84 

 88 

 88 

 88 

 85 

 85 

 87 

 89 

 88 

 87 

 88 

 87 

 86 

 80 

 83 

 84 

 85 

 84 

 S7 



°F. 

 51 

 52 

 60 

 55 



°F. 

 68 5 



19 













68 



20 

















71' 



21 







0) 











67-0 



22 















56 69- 5 



23 

















50 

 46 

 47 

 48 

 48 

 47 

 48 

 46 

 53 

 56 

 51 

 43 

 47 

 45 

 44 

 53 

 45 

 42 

 33 

 35 

 38 

 37 

 43 

 43 

 42 

 37- 



68-0 



24 









C 1 ) 









65-5 



25 















66-5 



26 



( 2 ) 



( 2 ) 













68-0 



27 



( 2 ) 





C 1 ) 







68-5 



28 











70-0 



29 

















70-5 



30 









( 2 ) 









65-0 



July 1 











C 1 ) 





70-5 



9 













72-0 



3 











( 2 ) 







69-5 



4 















64-0 



5 

















66-0 



6 

















66-0 



7 















66-5 



8 













( 2 ) 



( x ) 



70-5 



Aug. 3 













66-0 



4 















65-0 



5 

















60-0 



6 

















60-5 



7 

















59.0 



8 

















60-0 



9 

















63.5 



10 

















64.0 



11 

















63.0 



12 















( 2 ) 

 9 



61.9° F. 



62.0 



Incubation period (in days) 

 Average daily mean tem- 

 perature 



8 

 67.9° F. 



8 

 67.9° F. 



6 

 67.7° F. 



6 

 68.1° F. 



6 

 69.6° F. 



7 

 67.8° F. 













Deposited. 



2 Hatched. 



The mean temperature on the day of oviposition was not figured 

 in the average mean. 



