Saturday, May 31, 2014

Boxwood Leaf Miner - Monarthropalpus flavus (continued...fly stage)

In an earlier post, I captured photos of small Boxwood Leaf Miners- Monarthropalpus flavus (boring worms) that feed between boxwood leaf tissue.  In this post, I captured the worms, now emerging as pupae, transforming into adult flies.

Here, the leaf miner begins its emerging life cycle, by exiting through a hole and developing a pupae which hangs on the underside of last years leaf. Last year, adults laid eggs to overwinter in the tissue of the leaf. Eggs hatched in late April and began munching away until its time to begin the process of becoming a winged adult fly.
The leaves on the right, are last year's. On these leaves, you can see the pupae coating sheath which the adult fly shed. Once the fly cracks through this, it emerges and sits a while, until its wings have dried enough for flight.
I sat a while at the sight of all the activity. Flies buzz around, mate and then find the new flush of boxwood growth. They fixate their bottom end to the underside of the new tender leaves and poke holes - inserting their eggs for the next generation.
The flies time it perfectly. The tender new leaves have soft tissue, easy to poke their eggs into.
Interestingly, when it's windy, the flies have little success attaching their egg laying bottoms to the leaf. You can easily swat them away at this point.
I noticed this process has gone on for about two days. It's now late May, we've had brilliant sunny days and I suspect another day or two and all the egg laying will be done. Many adults were dead and left hanging up-side-down. It's a pretty short adult life span.

Best to prune the tips of growth a week or two after this process is complete. This removes the eggs and then the boxwood will respond with putting on new growth without any adults left to lay more eggs.

Neat process to witness entirely. Have a look at my previous post on Boxwood Leaf Miners - the worm stage.

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