The Sexual Strategy of Male Water Striders
Most people are familiar with Water Striders (Gerridae) insects that glide around on top of the water with the aid of water-repellent hairs on their feet that prevent them from breaking through the surface tension of the water. Something most people may not be familiar with is the duress that females are subjected to when it comes to strider reproduction.
Female Water Striders, who can store sperm from a single mating for weeks, are biologically inclined not to prefer reproduction for a couple of reasons. For one, after mating, the female has to carry to male around on her back for anywhere from a few minutes to two days, which seriously impairs her ability to forage for food.
Secondly, male Water Striders are the poster boys for sexual coercion, making it all but impossible for a female to reject their advances. With little if any warning, the male mounts a female. The female now has a choice as to whether to accept his advances. If she chooses to reject them, she doesn’t open the hard genital shield that covers her genital opening. In response, the frustrated male starts strumming the surface of the water which attracts predators such as Backswimmers from below. Because the female is closest to the water, she will be the one who gets injured from any attacks. Many a genital shield has been opened when the female has been put in this position. (Source: Beaty Biodiversity Museum) Photo: young Water Striders probably produced with the help of sexual coercion; inset-mating Water Striders)
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Hooded Mergansers Fledglings are Dispersing
Within 24 hours of hatching, Hooded Merganser ducklings leap anywhere from 8 -90 feet from their arboreal cavity nest down to their mother, who is calling to them from the water below. Capable of swimming and diving right away, the ducklings begin feeding themselves immediately. Weighing little more than an ounce, they mostly eat insects, including backswimmers, water boatmen and diving beetles. Eventually, as the ducklings grow, they work their way up to fish and crustaceans — particularly crayfish, such as the pictured merganser has caught. In addition to its size, the lack of a real “hood” indicates that this Hooded Merganser is a youngster.
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