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Posts tagged “Willows

Willow Beaked-Gall Midge

10-30-13 willow beaked-gall midge   047Now that most of the leaves have fallen, it’s a good time to look for galls that form on woody plants. Willows are host to a great number of gall-making insects, including tiny flies called midges. The most common species of willow gall midge is the Willow Beaked-Gall Midge, Rabdophaga rididae. In the spring, after mating, the adult female midge lays an egg in a willow bud (often terminal) that is just starting to expand. The egg soon hatches and the larva burrows deeper into the bud, which causes the bud tissue to swell and form a gall, usually with a “beak” at the top. The larva remains inside the gall through the winter, where it has a constant supply of food (the interior of the gall) and shelter. In the spring the larva pupates, and an adult midge emerges and begins the cycle all over again. Some gall midges are crop pests, but willows are not significantly damaged by the Willow Beaked-Ball Midge.

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Pine Cone Willow Gall

Galls are abnormal plant growths that can be caused by insects, fungi, bacteria, nematode worms and mites.  Insects cause the greatest number of galls and induce the greatest variety of structures.  Galls provide both food and shelter for the organisms living within them.  Galls develop during the growing season, often in buds and on leaves.  Pine Cone Willow Galls, named for their resemblance to small pine cones, are found on willows, typically in terminal buds.  A gall midge (Rhabdophaga strobiloides) is responsible for the willow bud going haywire and developing  abnormally. (No-one has determined exactly how insects cause galls, whether it’s the act of laying eggs in or on the plant, or if it’s somehow connected to the chewing of the larvae into the plant.)    Each gall-making insect has a specific host plant, or small group of related plant.  The galls that each insect species induces and lives in while developing into an adult has a recognizable shape and size.  When you think you’re seeing pines cones on willow trees, you’re not hallucinating, you’ve just discovered the temporary home and food supply of a tiny fly, known as a midge.


Beaver Diet

In March and April, beavers consume a lot of tree bark, but come summer, approximately 90 % of a beaver’s diet consists of grasses, aquatic plants, and other herbaceous vegetation.  Of the woody plants that they do eat during the warmer months, aspen/poplar (in photograph) and willow are favorites.  It appears that beavers use their sense of smell in order to find their tree of choice.  The greater the distance from the pond, the more selective beavers are in terms of species chosen – they go as far as a tenth of a mile away and up steep slopes for aspen!