Fall is a great time of year to take a look at leaves, and the freaky ways in which insects can modify plants into houses for their larvae, producing a huge variety of freaky growths called galls.

The majority of insects that produce these structures are tiny gnats or wasps.  The plant tissue responds to their invasion by producing extra tissue in a sort of decorative tumor.  These little structures then become both protection and food source for the developing larvae–the ultimate bug condo.

The really fascinating thing about galls?  The same plant will respond to different species of insects in different ways. That produces galls that are distinctive enough to be characteristic of individual species of insects.

Here’s an assortment of beautiful galls–click the photos to see the originals.

Why are they called Galls? Entomological lore has it that because woody plants are most commonly attacked by gall-making insects, these structures often have lots of tannins in them. Which would make them taste bitter–hence, Gall.  Oak galls were often collected and used for tanning animal skins in Europe, as well as a source of dyes and inks.

A challenge for my more taxonomically advanced readers–can you name these gall makers?

Posted by Gwen Pearson

Writer. Nerd. Insect Evangelist. Have you heard the good news? BUGS!


  1. Since they have a lot of tannins in them, would they be useful in cooking or adult beverage making?? Or are they just disgusting lol

  2. I’m sure some of them are edible—but I wouldn’t want to be the one to try them :)
    They certainly are used to make a wide range of dyes–heres a net set of examples http://tinctory.blogspot.com/2009/10/oak-galls-dye.html

  3. Very beautiful – the last one in particular looks like a handful of ripe berries more than anything created by insects!

  4. Haha, nice! The first question about these amazingly diverse and biologically interesting thingies is… if you can eat or drink them. That is just so human! ;)

    Does anyone know if there’s a guide somewhere out in the webz to identify at least some common forms?

  5. Every day is a school day!

    I spotted this (http://twitpic.com/7d4ies) whilst out walking in South Wales when visiting my Dad in February and I had no idea what it was so I snapped a picture with my IPhone. I had forgotten about it until today when I was reading this blog and now I finally know it is a rose gall.
    I would never have guessed it was caused by insects.

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