Wednesday, June 29, 2016

Dogwood Leaf Gall

I found this gall on the underside of a Gray Dogwood leaf tonight. The upper side had only a faint dimple on the surface. This was the only one I found.  A review of Bugguide identified it as Craneiobia tuba,  one of the many gall midges (Cecidomyiinae).  The larva are said to be orange and the adults haven't been raised.  And that was the end of what is known about them.

Tiny gall midge 0.1 inch- Wikipedia
Gall and wood midges (Cecidomyiidae) are a large family with over 1000 species in our area.  Bugguide describes them as "minute, delicate flies (1-5 mm) with long legs and usually relatively long antennae, and with reduced wing venation.  With their tiny size and cryptic lifestyle, it is no surprise that  so little is known about most species.  Even photographing their larva in the galls is a major challenge.

Gall Midge adult- Charley Eiseman
The Wikipedia article has more than you want to know about their genitalia and other anatomical structures.  It is sufficient to say that they have a broad range of lifestyles and some are even predators or parasitoids of crop pests such as aphids and scale insects.  Most however lay their eggs on plants, forming galls where their larva develop using the plants resources.  Given my passion for galls, 1000 species to learn should last me a while.

This gall lives on a very common but economically unimportant species, the Cornus or Dogwoods.   Research is funded primarily by studying insects that affect agricultural plants, or "follow the money" as they said in All the Presidents Men.  It is unlikely that a formal study will focus on this species in the near future.  Not that C. tuba cares.  It is doing quite well without our attention.

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