Leaf-rolling Weevils

I love how each little discovery leads to another.  Today I was walking the trail at Holland Glen in Belchertown, MA, with some members of the Kestrel Land Trust, for whom I will be leading an animal tracking walk this Sunday on a parcel they are in the process of protecting.  (They think we’ll be tracking the kinds of animals with bones and fur.  We’ll see how that goes.)  Early on in the walk, I spotted a tiny moth resting on a witch hazel leaf, and noted its location because I wanted to come back and get a picture of it–I suspected it was Cameraria hamameliella, the species whose blotch mine is shown on p. 349 of my book, and it’s always nice to be able to put a “face” to the insect signs I’ve documented.  I returned an hour later, after everyone had left, and miraculously the moth was still there.

A Cameraria (apparently C. corylisella) resting on a witch hazel leaf. (4 mm)

(I showed this picture to Terry Harrison, creator of the excellent website microleps.org, and he said the moth most closely matches Cameraria corylisella, a species that mines in hazelnut, musclewood, and hophornbeam.  I guess I’ll just have to collect some C. hamameliella mines if I want to get a photo of this species.  On the plus side, this seems to be the first photo of C. corylisella on the Web.)

I spent another hour or so exploring the area, taking pictures, and collected some distinctively folded and rolled witch hazel leaves in the hope of raising the caterpillars inside and finding out what moths are responsible (I’ll write about these later if I succeed).  Eventually, I made it back to my car, and I was just about to get in when I saw a hover fly resting on a leaf.  I haven’t had many chances to photograph these with my good macro lens because they tend to fly away when a big lens is thrust within a few inches of them, but this one seemed pretty relaxed so I decided to give it a shot.

Hover fly (Syrphidae: Syrphus; 1 cm) and honeydew.

As I was taking pictures, I noticed a dent in the fly’s thorax and wondered if this had something to do with its relative tameness.  But then I snapped out of my tunnel vision and realized that the fly was focused on sipping the spots of honeydew that were covering the leaf it was on.  I looked up to see if I could find the source of the drips, and I saw a cluster of three treehoppers on a red oak twig about two feet overhead.  I pulled down the branch to get a closer look, and two of them hopped off but the third was willing to have its portrait taken.

Treehopper (Membracidae: Smilia camelus) on red oak. (9 mm, including wings)

When I was done with the treehopper, I turned my attention to a nearby leaf from which an amorphous object was hanging.  When I pulled it closer, I saw that it was the leaf roll (nidus) of a leaf-rolling weevil.  And when I put my lens to it, I saw that the weevil was still perched on top of it!

An oak leafrolling weevil (Attelabus bipustulatus) perches atop her ~7 mm leaf roll.

Leaf-rolling weevils (Attelabidae) roll up these little packets as food for their larvae.  They do so essentially using origami, without applying silk or any other adhesive.  Each leaf roll contains a single egg, and when the egg hatches the larva will eat the tissue inside the roll.  As I took pictures of this weevil, she milled about a bit on the leaf for a few moments and then moved to the base of the leaf roll, which she nibbled until the roll dropped to the ground.

The weevil nibbling the base of the leaf roll to detach it from the leaf.

An instant before the leaf roll dropped to the ground.

Not all leaf-rolling weevils detach their leaf rolls like this, since they can be found still attached to the leaves after the weevils have gone, and I’m not sure if it’s even typical for this species.  Perhaps doing so makes it harder for the leaf rolls to be found by the thief weevil (Pterocolus ovatus), a rogue attelabid species that eats the eggs of other leaf-rolling weevils and then deposits its own egg inside the leaf roll.

A closer look at the oak leafrolling weevil (Attelabus bipustulatus). (~3 mm)

This was only the third time I’ve found attelabid leaf rolls.  The ones pictured in the book were spotted by Noah Charney at the edge of a parking lot in Virginia on our road trip in the summer of 2008.  I found a single leaf roll on a musclewood leaf in Ohio last month, among the many leaves bearing flea weevil mines.  But, as with so many of these fascinating insect signs, there was no need to travel far to see them; this was only a few minutes from my house.  It’s just a matter of being in the right place at the right time.  I never would have seen this if I hadn’t gone back to photograph the moth on the witch hazel; if I had returned to my car a minute earlier the hover fly might not have been there to cue me to look at the oak branch above me; and if I had stopped to photograph one more bug the weevil would have already snipped the leaf roll and flown away before I got there, and I would have missed the whole thing.