Monday, November 17, 2014

Acorn Weevil

This August I found this long-nosed beetle in a patch of oak trees.  Although it looks dangerous with a snout almost as long as its body, you should "fear no weevil," for it attacks only plants.  With its long slender beak and its sharply elbowed antennae, it is identified as a nut and acorn weevil, a member of the genus Curculio with over 30 species on our continent.  Many of these make their living on oaks.

Curilio female weevil.  Females have the longer beak
Last week we traveled to Taneyville to make nature mobiles with the 5th grade class.  The class had collected a variety of nature finds for elements on the mobiles including bags of acorns.  At the end of the session, John Shelton came up to me and generously offered me part of his collection of acorns to use for another class.  I sealed them in a ziplock bag and 24 hours later I found a Curculio larva in the bottom of the bag adjacent to a newly drilled acorn.

Once out of the bag, it laid still for a minute and then started to make its getaway, looking for some nice soil to pupate in for a couple of years.  It was slow moving so I had lots of time to set up for this macro movie to document its progress.

Inserting the egg - USFS

Life begins for a weevil when a female bores into a green developing acorn and deposits a single egg.  She seals up the tiny hole with her fecal material and the larva will emerge from the egg to find shelter and sustenance.  After consuming most of the nut's contents, it carves out a round hole and struggles out of the acorn.  The larva will then crawl off into the soil to pupate.

The pupa may not emerge for over a year, coming out as an adult in the summer, hopefully at the time the acorns are greening up.  After mating, the female begins a long climb up a mature oak to start the cycle again.

Larva in acorn - USFS
The whole process is shown in this short National Geographic video.

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