ENTOMOLOGY

.~44 SANITARY ENTOMOLOGYMitzmain found the minimum life cycle of Tabanus striatus in thePhilippines to be 52 days.The life cycle of Taba'TI/US lasiophthalmus was found by Hine in oneinstance to be about 9 months.. He states that the cycle of Tabanusst'!Jgius probably requires two years.As has already been indicated in discussing larval periods, it isprobable that the species of Tabanus in the Sierra Nevada Mountainsrequire two seasons for their life cycles.HABITS OF ADULTSOnly female adult horse flies attack stock (plate XIX). The malesare never found taking any interest whatever in warm-blooded animals.Their food consists of the nectar of flowers and other sweet substances.Females also feed readily on sweet substances. I have quite often captureda few in a fly trap baited with banana. It appears that the primaryobject of the blood meal is to enable the female to develop eggs, althoughthis diet may also be taken. for nourishment. .The males are usually to be found in the grass, or the foliage of trees,or on the trunks of trees, and when the females are not sucking bloodthey will usually be found in the same situations.In temperate climates females are most active on still, sunshiny days.It is unusual to find them flying on cloudy days or when strong wind isblowing.In taking a meal of blood a female Tabanus will usually insert andwithdraw the beak several times, puncturing the skin of the host in anew place each time, before finishing the meal. The length of timeoccupied in taking a meal in cases observed by the writer has varied fromabout 3 to 11 minutes, and during this time the position may be changed5 or 6 times. Mitzmain has seen Tabanus striatus in the Philippines feedfor 23 minutes. I have allowed flies to bite my arm and feed to satiety.It is not a continuously painful process. The only part of the performancethat is painful is the insertion of the beak, which takes but afew seconds. After that ihe drawing of the blood by the fly causes nosensation whatever in the arm. However, the habit of changing positionso often during a meal is somewhat annoying.Horses are much more nervous under the attacks of Tabanus thancows. The latter often allow the flies to feed without much of anyattempt to brush them off, but a horse fights constantly. Where theattack is severe, the horses in a pasture will bunch up together formutual protection in rubbing against each other. Under such conditionsit is possible that each fly will attack several horses, being brushed offseveral times before the meal is finished. This makes an ideal condition