ENTOMOLOGY

BIOLOGY AND HABITS OF HORSE FLIES 239accused of causing the death of camels, from grasses and weeds overhangingrain pools. These masses were placed on the upper sides ofthe plants as they hung over the water.In Ohio, Hin:e records finding the egg masses of Tabanus stygius Sayprincipally on the leaves of Sagittarin standing in shallow water, thefemale fly llabitually placin~the eggs just above the point where thepetiole meets the expanded part of the leaf.l'Iibmain, working in the Philippines, used a large cage to secureovipositions of Tabanus striatus Fabricius. He found that egg layinginvariably took place in the early afternoon, never later than ~ o'clock.Under cage conditions egg masses were deposited on projecting splintersof wood, suspended fibers of jute sacking, fine brass wire, a. single animalhair, coarse iron wire, leaves of trees, and the woodwork on sides andceiling of the cage, invariably upon the shaded portions,-as the undersidesof beams and partitions. The egg mass in Borne cases entirelysurrounded the object on which it was deposited. The cage contained 0.tank of water 'with growing water plants. Apparently l\Iitzmain didnot find eggs in the open.In Southern Nigeria, Neave found the eggs of TabanUll corax Locwin the bush on reeds or grasses overhanging mud.Near Alturas, California, during the past two seasons, I have foundthe egg masses of an unidentified Tabanus, to be very abundant on theundersides of leaves overhanging a small creek. They were found on theleaves of willow, alder, and rose bush; also occasionally on the leavesof Populus and on coarse grass blades.I have never been fortunate enough to observe the process of egg laying,although on one occasion I came upon a female of Tabanus punctiferwhich had just finished ovipositing, and was still in position, head downwardson a stem of coarse grass. She was occupied at the time in brushing'theend of the abdomen over the pure white egg mass, apparentlycovering it with a. kind of transparent cement. She was not disturbedby my close approach. In fact, I broke off the stem on which she restedand observed the brushing process at close range for some little timebefore she took flight.:Seave mentions the fact that the eggs of Tabanus corax in SouthernNigeria arc covered with an almost impervious cement. On one occasionan egg mass of this species, after being kept for two days in 70 percent alcohol, produced a few larv&! after being taken out of the alcohol.However, not all species of Tabanus cover the eggs with cement. Theeggs of TabanUll phaenops in the Sierra Nevada Mountains are not socovered, and fall from their place of attachment soon after hatching.The number of eggs contained in the mass varies considerably. Theeasiest way of ascertaining the number in any given mass is by counting