VIII, B, 3 Mitzmain: Biology of Tabanus striatus Fabricus 199 



The eggs are laid in a compact mass either extended on a flat 

 surface or surrounding various attached objects, usually of 

 small diameter, such as projecting splinters of wood, sus- 

 pended fibers of jute sacking, fine brass wire, a single animal 

 hair, and coarse iron wire. Upon these materials the eggs 

 are laid in an ellipsoidal form sometimes surrounding the 

 objects completely or nearly so. On one occasion 2 egg masses 

 were found upon a small splinter of wood which they entirely 

 enveloped. The surfaces of the egg masses were continuous, 

 so that the double mass resembled a single large one. When 

 eggs were found deposited on a flat surface, on two occa- 

 sions a leaf was the object selected. These were leaves of 

 an ornamental plant which was used for shade purposes in the 

 breeding cage. The plant in question grew close to the cement 

 water tank in the breeding cage. In all other instances the 

 eggs were deposited upon woodwork on the sides and ceiling of 

 the cage, invariably upon the shaded portions, as the underside 

 of beams and partitions. In egg laying upon flat surfaces there 

 was a strikingly constant geometric form. Usually the form 

 assumed was roughly a pentagon with a biconvex center. 



At the beginning of oviposition usually 2 eggs are deposited 

 in the position of an inverted V. Three to 4 eggs are then laid 

 on either side of the apex of this V, and then one side and then 

 the other is built up, rather irregularly at first, until the sides 

 of the pentagon are completed. The eggs are laid cleanly and 

 definitely, each line slightly overlapping that preceding. When 

 the eggs are laid in the extended order, they are deposited 3 or 4 

 layers in depth, but usually as many as 6 layers are required to 

 complete the mass when the eggs surround a convex object. 



In the process of laying, the body is held away from the egg 

 mass, the legs being planted firmly. When the eggs are attached 

 to an object above, the insect stands with head downward, the 

 forelegs suspended alongside the head, the hind and middle legs 

 supporting the weight of the body. At the first movement, the 

 anal end of the body is bent toward the thorax under the 

 abdomen, and with a slight jerk the egg is laid, while the brush- 

 like appendage of the ovipositor exudes a tiny drop of liquid 

 coating the egg as it is deposited. The movement of deposition 

 is very much like squeezing a bit of pasty material from a 

 collapsible metal tube. 



In several counts that were made, the fly was observed to lay 

 with clock-like precision at the rate of 10 eggs per minute. 

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

 below the fly. In three instances observed, the process occupied 



