Friday, Jan. 4, 2002
* Japanese name: Akaushiabu
* Scientific name: Tabanus chrysurus
* Decription: This is a stout-bodied insect with huge, iridescent compound eyes (the eyes touch in the center in males but are separated in females). They have one pair of wings and are strong fliers, able to cover long distances. The thorax and abdomen are yellow and black. Horseflies are 25-30 mm long.
* Where to find them: Mainly in suburban and rural areas, from Hokkaido to Kyushu, where they are pests of mammals, especially horses, but also humans. Adults emerge in June and mate soon afterward. Sex is initiated in the air and completed on the ground. Adults live for three-four weeks, during which females lay batches of 100-1,000 eggs covered in a jellylike material, on rocks near water or on leaves overhanging water. When the eggs hatch, the fat, white maggots fall into the water or moist soil.
* Food: Both males and females eat nectar, but females need a blood meal in order to produce eggs. The larvae eat other insect larvae, snails and earthworms. Adults locate their prey chemically (homing in especially on carbon dioxide) and when closer, visually.
* Special features: Horseflies, as anyone who has been bitten by one will know, have formidable mouthparts. Shaped like a miniature pair of steak knives, the mouthparts are made of two slender mandibles. Rather than sucking blood like a mosquito, horseflies repeatedly slash the skin, forming a deep wound in which blood collects. The fly then laps up the pool of blood with a tonguelike mouthpart. Sometimes, minor secondary bacterial infections may occur after humans are bitten by a horsefly, but these are never serious. On the other hand, horseflies can transmit diseases, including anthrax, to domestic animals.