ENTOMOLOGY

BIOLOGY AND HABITS OF HORSE FLIES 237The larval stage of most species is passed in the ground, and ll.certain degree of moisture is necessary for proper growth and development.JUost species !equire very wet, or saturated soil, others are ableto develop in moderately moist earth.EGGS .AND EGG LAYINGThe eggs are deposited by the female fly in clumps of several hundredeach, on vegetation, rocks, or other objects overhanging suitable placesfor development of the larvre. When the eggs hatch, the young larvredrop to the soil or water beneath and disappear from sight. Here theyremain for several months, sometimes for one or two years, when, afterpassing through a short pupal period, they emerge as adult lfIies.In some cases the .egg mass as well as the place of oviposition is·characteristic of the species, and renders identification easy, once theobserver sees one of which he knows the identity.In the Sierra Nevada Mlountains of Eastern California where I han!been studying tabanids for the past two years, the egg masses of the twomost important species are very easily distinguished. '.rhe egg mass ofTabanus pwnctifer Osten Sacken is oblong, somewhat pyramidal in shape,and about the size of the end of a man's little finger (plate XX, fig. 1).It is usually deposited-upon a bull rush or coarse grass stem, and fromone to three feet above the surface of the soil or water. When deposited,as is the case with all horse fly eggs, the mass is milk white. In a day or80, however, the color darkens to a mottled gray and white. Eggs of thisspecies arc found most abundantly along lake shores. The egg mass ofTabanus phaenops Osten Sacken is to be found on grass blades, threeor four inches above the soil in swampy places in meadows. This mass isconsiderably smaller than that of Tabanus pwnctifer, is elongate, andusually contains but two layers of eggs, while t.he other species usuallyhas about fi,'e layers. The egg mass of T. phaenops is black a day ortwo after oviposition. This mass is inconspicuous and extremely hard tolocate in nature.In the Egyptian Sudan, Harold King found the eggs of Tabanuskingi Austen deposited in rounded masses on rocks rising from the edgeof a stream, generally overhanging the water, and from 6 inches to 15inches above the water level. He also found the masses of Tabanusditaeniatus Macquart on grass growing in rain pools. The shape of theegg mass of this species was variable,-some being long and narrow,others short and broad. The same worker secured ovipositions ofTabanus par Walker in a cage, on the under sides of leaves of a waterweed growing in a vessel of water. He also secured the egg masses ofTabanus taeniola Palisot de Beauvois, the tabanid most frequently