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Posts tagged “Insect Adaptations

Spittlebugs

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Have you ever poked around inside one of those masses of bubbles that you see on grass and other plant stems? If so, chances are that you have discovered that an insect actually lives inside this frothy home – the immature stage (nymph) of a Spittlebug. It hangs head down while piercing the stem of the plant and ingests the sap. Because the sugar content is often very low, the nymph must drink a lot of sap in order to get the nutrition it needs. As a result, the Spittlebug pumps out the excess water from the tip of its abdomen, which amounts to 150 – 300 times its weight every 24 hours. During this process, oxygen and nymphal secretions cause the water to have a sticky, bubbly quality, and these sticky bubbles pour down over the nymph, creating a moist home that prevents the Spittlebug nymph from drying out and that discourages predators as it tastes bad. Once it has matured, the nymph metamorphoses into an adult Spittlebug (also called a Froghopper) and flies away.  (Photographs are of:  spittlebug “spit,” spittlebug nymph and adult spittlebug emerging from nymphal skin.)


Larvae-seeking Downy Woodpeckers

12-3-11  Larvae-seeking Downy Woodpeckers

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When cooler days arrive and adult insects become relatively scarce, insect-eating birds are very clever at gleaning the twigs, trunks and buds of trees and shrubs for overwintering eggs, larvae and pupae.  Certain galls (abnormal plant growths that house and provide food for a variety of insects) are sought by specific birds.  Downy woodpeckers seek the larvae of the Goldenrod Gall Fly (Eurosta solidaginis), which overwinter inside Goldenrod Ball Galls (formed on Canada Goldenrod, Solidago canadensis) before emerging as adults in the spring.  A tiny1/4” to 3/8”-wide hole (and an empty gall) is evidence that a downy woodpecker had itself a meal!

   


Some Monarchs Outwit Milkweed

We think of monarch larvae as being impervious to the  ills of milkweed, but they are very vulnerable when it comes to the sticky latex in the sap of their host plant.  The mandibles of young monarch caterpillars are often glued together by this latex, preventing them from eating.  Research shows that about 30 percent of monarch larval loss results from miring  in this glue-like substance.  One strategy young larvae use is to chew a near circle in a milkweed leaf, blocking the flow of latex to the enclosed surface area, which they then eat.  If a monarch survives the first few stages, or instars, of its larval life, it uses yet another strategy to circumvent the latex.  Older, larger larvae often cut through the midvein of a leaf they wish to consume, which dams the latex flow to the entire leaf beyond the cut.  Look for limp leaves as you peruse a milkweed patch.  If you find one, you may be rewarded with the nearby presence of a monarch caterpillar.