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Jewelweed Gall Midges

10-4-13 jewelweed gall  277Abnormal plant growths called galls come in all sizes and shapes, are found on leaves, buds and stems, and are caused by a number of agents, including insects. A majority of insect galls are caused by the eggs and developing larvae of flies, wasps and midges. Jewelweed, or Touch-Me-Not (Impatiens capensis), has a very distinctive looking aborted bud gall that is produced by a midge (Schizomyia impatientis). While some galls provide shelter and food for a lone resident, the Jewelweed Gall Midge is colonial, and several orange larvae can be found residing in separate cavities within the gall. These midge larvae are now emerging and will overwinter as adults.

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7 responses

  1. Louise Garfield

    The world of galls is so interesting. Yesterday I saw sumac gall aphids!

    October 4, 2013 at 1:16 pm

  2. micky

    Could you clarify what causes a gall? I have assumed that the mother insect injects something into the plant to cause the growth. You says that the gall is caused by the eggs and larvae. Perhaps it is different for different species.
    Thanks fo another fascinating post.

    October 4, 2013 at 1:42 pm

    • As Cliff Fairweather so accurately described, “Gall formation is usually induced by substances in the saliva of the larvae that basically hijack a growing part of the plant and force it to form an organ under the control of and for the benefit of the gall-maker. Mechanical stimulaiton also appears plays a role in the case of aphid-like gall makers, such as those that form cone galls on witch hazel leaves.”

      October 4, 2013 at 3:31 pm

      • micky

        Thank you. I stand (or sit) corrected.

        October 4, 2013 at 5:40 pm

  3. Kathy Schillemat

    What do you know about oak galls? We have found some interesting galls on the ground and in the leaves of oaks.

    October 4, 2013 at 2:33 pm

    • The oak family has a huge variety of galls — a great place to look!

      October 4, 2013 at 3:31 pm

  4. Cliff Fairweather

    Thank you for highlighting the underappreciated phenomenon of galls! Gall formation is usually induced by substances in the saliva of the larvae that basically hijack a growing part of the plant and force it to form an organ under the control of and for the benefit of the gall-maker. Mechanical stimulaiton also appears plays a role in the case of aphid-like gall makers, such as those that form cone galls on witch hazel leaves.

    October 4, 2013 at 3:06 pm

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