BIOLOGY AND HABITS OF HORSE FLIES 239 



accused of causing the death of camels, from grasses and weeds over- 

 hanging rain pools. These masses were placed on the upper sides of 

 the plants as they hung over the Avater. 



In Ohio, Hine records finding the egg masses of Tahanus stygius Say 

 principall}^ on the leaves of Sagittaria standing in shallow water, the 

 female fly habitually placing the eggs just above the point where the 

 petiole meets the expanded part of the leaf. 



Mitzmain, working in the Philippines, used a large cage to secure 

 ovipositions of Tahanus striatus Fabricius. He found that egg laying 

 inA'ariably took place in the early afternoon, never later than 2 o'clock. 

 Under cage conditions egg masses were deposited on projecting splinters 

 of wood, suspended fibers of jute sacking, fine brass wire, a single animal 

 hair, coarse iron wire, leaves of trees, and the w^oodwork on sides and 

 ceiling of the cage, invariably upon the shaded portions, — as the under- 

 sides of beams and partitions. The egg mass in some cases entirely 

 surrounded the object on which it was deposited. The cage contained a 

 tank of water with growing water plants. Apparently ]\Iitzmain did 

 not find eggs in the open. 



In Southern Nigeria, Neave found the eggs of Tahanus corax Loew 

 in the bush on reeds or grasses overhanging mud. 



Near Alturas, California, during the past two seasons, I have found 

 the egg masses of an unidentified Tabanus, to be very abundant on the 

 undersides of leaves overhanging a small creek. They were found on the 

 leaves of Avillow, alder, and rose bush; also occasionally on the leaves 

 of Populus and on coarse grass blades. 



I have never been fortunate enough to observe the process of egg lay- 

 ing, although on one occasion I came upon a female of Tahanus punctifer 

 which had just finished ovipositing, and was still in position, head down- 

 wards on a stem of coarse grass. She was occupied at the time in brush- 

 ing the end of the abdomen over the pure white egg mass, apparently 

 covering it with a kind of transparent cement. She was not disturbed 

 by my close approach. In fact, I broke off the stem on which she rested 

 and observed the brushing process at close range for some little time 

 before she took flight. 



Neave mentions the fact that the eggs of Tabanus corax in Southern 

 Nigeria are covered with an almost impervious cement. On one occasion 

 an egg mass of this species, after being kept for two days in 70 per 

 cent alcohol, produced a few larvae after being taken out of the alcohol. 

 However, not all species of Tabanus cover the eggs with cement. Tlie 

 eggs of Tahanus phaenops in the Sierra Nevada Mountains are not so 

 covered, and fall from their place of attachment soon after hatching. 



The number of eggs contained in the mass varies considerably. The 

 easiest way of ascertaining the number in any given mass is by counting 



