WERNER MARCHAND 147 



In several counts that were made by Mitzmain, the fly was observed 

 to lay with clock-like precision at the rate of ten eggs per minute. 

 This did not vary whether the attached object was above or below 

 the fly. In three instances observed, the process occupied from forty 

 to forty-five minutes. Both the beginning and completion of the 

 egg-laying process 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 imme- 

 diately begins to deposit a new egg mass. This was twice repeated 

 with one female, and three distinct egg masses were deposited, all 

 identical in geometrical arrangement. 



The eggs of this species of Tahanus are laid with very little cement- 

 ing material. The cement used is a transparent substance "and not 

 dark and opaque as found to exist in the species described by Hine" 

 {Tahanus lasio phthalmus) . The cement provided by this species 

 was tested and found to be water-proof, as well as insoluble in various 

 grades of alcohol and xylene. 



The eggs (Plate 2, Fig. 25) 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 

 lengthwise for nearly 0.5 mm. from the end opposite the micropyle. 



The shape of the individual egg is that of the muscid t)^e 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 mm. 

 The size of the mass varies from 9 to 12 mm. in length by 6 to 9- 

 mm. in breadth. 



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



Mitzman gives a detailed description of the hatching process. 

 Two egg masses were observed microscopically during the entire 

 process of hatching, and fourteen egg masses were noted as to the 

 length of the incubation period. The minimum period observed 



