VIII, B, 3 Mitzmain: Biology of Tabanus striatus Fabricus 201 



first signs of these were seen in the two eggs which formed the 

 nucleus for the egg mass and which are the first eggs laid. 

 These movements, as indicated by either of the dark eye spots, 

 could be seen with a hand lens at intervals of a few seconds; 

 their action was similar to that of the bubble in a spirit level. 

 In about an hour the movement was seen to be rather general 

 in the egg mass, accompanied in the eggs first laid by an alternate 

 collapsing and distending of the exochorion. This action is the 

 result of the torpedo-like movement of the head capsule of the 

 embryo in the direction of the micropyle of the egg. The move- 

 ment is effected by the piston-like action of the apophyses of the 

 cephalopharynx, which appear to work alternately, bringing the 

 saw-toothed mandibles in contact with the micropyle canal. 

 These movements proceeded uninterruptedly during the hours 

 of the night, the only change observable being that the body 

 segments of the embryonic larva became better defined. At 

 4.25 the next morning the segments of the embryo could easily 

 be counted through the chorion. The dorsal surface of the exo- 

 chorion was seen to be slightly shrivelled. 



Fully one hour and thirty minutes intervened during which 

 there was no action worth noting. This quiescence was inter- 

 rupted by a sudden remarkable activity of all of the visible eggs 

 of the mass. At 6.08 there was a general upheaval of the 

 surface of the egg mass, an agitation within the eggs, and an 

 alternate collapsing and distending of the eggshells. At 6.10 

 the first layer of eggs gave birth to a silvery horde of young 

 larvae, which at 6.12 had crawled from view. Then ensued 

 another spasmodic agitation giving birth to another lot of larvae, 

 which crawled from the mass of empty eggshells. The emer- 

 gence which is effected by the head structures is aided by the 

 posterior protuberances, which functioning as prolegs push the 

 body of the larva clear of the eggshells. 



MORPHOLOGY AND HABITS OF THE YOUNG LARV.E 



Immediately after emerging from the egg, the young larvae 

 seek concealment. In nature, no doubt, resort would be had to 

 the convenient water course where aquatic plants, drift wood, 

 and stones would be the probable hiding places. The larvae 

 under observation became very active and crawled out of the 

 stender dish, a height of 9 centimeters, and tumbled into the 

 water of the basin provided. When collected and placed in a 

 deep glass vessel with some water, the entire mass took refuge 

 behind the filter paper in the glass. Here they crowded side to 

 side with their siphons projecting from the upper edge of the 



