200 The Philippive Journal of Science ms 



from forty to forty-five minutes. Both the beginning and com- 

 pletion of the performance were without deliberation, the insect 

 walking away from the mass of eggs and flying off as soon as the 

 last egg was deposited. 



When disturbed during oviposition, the insect does not fly and 

 can readily be carried without attempting to escape. While in 

 the act of laying, if interrupted and dislodged from the position, 

 it immediately begins to deposit a new egg mass. This was 

 twice repeated with one female, and three distinct egg masses 

 were deposited, all of them identical in geometrical arrangement. 



The eggs of this species of Tabanus are laid with very little 

 cementing material. The cement used is a transparent sub- 

 stance and not dark and opaque as found to exist in the species 

 described by Hine.(l) The cement provided by this species was 

 tested and found to be waterproof, as well as insoluble in various 

 grades of alcohol and xylene. 



The eggs when laid are a pale clay yellow, but within twenty- 

 four hours become slightly darkened with an ashy gray tinge. 

 Microscopically fine black striations can be seen running length- 

 wise for nearly 0.5 millimeter from the end opposite the 

 micropyle. 



The shape of the individual egg is that of the muscid type 

 with more sharply pointed ends; it is not quite spindle-shaped. 

 Several eggs were measured and found to average in size 1.6 by 

 0.4 millimeters. The size of the mass varies from 9 to 12 milli- 

 meters in length by 6 to 9 millimeters in breadth. 



The number of eggs laid in a mass varied greatly. In 4 

 masses counted, there were respectively 270, 340, 417, and 425. 

 Ten masses dissected from the bodies of killed flies were found 

 to average 405 ; the greatest number found in any female was 495. 



THE HATCHING PROCESS 



Two egg masses were observed microscopically during the 

 entire process of hatching, and 14 egg masses were noted as to 

 the length of the incubation period. The minimum period 

 observed was three days and the maximum five days. Four 

 days is probably the average length of time required for in- 

 cubation. It was observed that the degree of temperature and 

 moisture influenced the time of hatching. Slight changes in 

 either of these factors can be used to control the time of 

 emergence from the egg. The following is a series of observa- 

 tions on the hatching of an egg mass. 



Twenty-two hours previous to the hatching of the embryo, 

 certain unmistakable activities were discernible in the egg. The 



