The Triumph of Weevil
Imagine living your life with a 10-foot–long straw fastened to your face, like this acorn weevil does. That protrusion, called a rostrum, is highly useful for the weevil, however, allowing it to feed and to lay eggs. But to the oak trees that these weevils often feed on, it’s a potentially hazardous instrument.
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DownloadThe Triumph of Weevil
Imagine living your life with a 10-foot–long straw fastened to your face, like this acorn weevil does. That protrusion, called a rostrum, is highly useful for the weevil, however, allowing it to feed and to lay eggs. But to the oak trees that these weevils often feed on, it’s a potentially hazardous instrument.
What am I looking at?
This is a female acorn weevil (Curculio glandium). Take a close look at the end of its long rostrum, which terminates in tiny chewing mandibles (1). You can also see the geniculate antennae (2) that extend from its rostrum (“geniculate” refers to the elbow-like bends in the antennae), as well as one of its compound eyes (3).
Click on the right arrow to see additional views of this weevil.
Biology in the background
These weevils are native to eastern North America and mainly feed on the nuts or seeds of trees. They often use their rostrum to drill holes in acorns, either to eat the fruit within or to lay their eggs inside the shell. After the eggs are deposited in the developing acorn, the tree heals the hole, protecting the egg and the young weevil from predators and parasitoids. Once the larvae hatch, they eat the fruit within the acorn. Then, after an acorn drops to the ground, the larva inside it chews a hole in the shell and leaves the acorn to pupate in the ground. These weevils can be a significant threat to acorn-bearing trees, because acorns that contain weevil eggs or larvae cannot germinate; sometimes, 70% to 90% of a tree’s acorns will be unable to germinate.
The body of an acorn weevil can grow up to 8 millimeters long, or about a quarter of the size of a human thumbnail. However, its rostrum can be over twice that length, up to 17 millimeters long, or slightly smaller than a human thumbnail.
Technique
These images were created using macrophotography.
TagsIgor Siwanowicz, HHMI's Janelia Research Campus