Tiny Braconid Wasp

03rd July 2012
When I was photographing the Ectemnius wasp described in my previous Blog post, I noticed that the leaf the wasp was on, contained some aphid "mummies". These occur when aphids have been parasitised by tiny Braconid wasps. The Braconid larvae develop inside the aphids, finally emerging and just leaving a "shell". I thought that photographing some of these "mummies" would provide something interesting for a new Blog post.

I went back to the same plant and brought it inside. There were several live and mummified green aphids on the plant. When I was examining them with a hand-lens, I was surprised to see that there was also a tiny wasp investigating the aphids. I hurried for my camera! Photographing this would be a challenge, as the wasp was only about 2mm long. It would need my MP-E 65mm Macro lens extended to its maximum. This gives a 5:1 "magnification" but with an exceptionally narrow depth-of-field and a rather dark view through the viewfinder.

It was difficult locating the wasp on the leaf, but I kept checking with my hand lens and then trying to locate it with the camera lens. I had the leaf flat on a table and the lens on a cushion to minimise movement and vibration. Whenever I managed to locate the wasp, I tried to follow it around the leaf, photographing as it went. Fortunately, the hairs on the leaf presented the wasp with considerable obstacles, which slowed it down. Whenever it encountered an aphid though, it stopped to examine it and then injected it with a egg. It did this to a dozen or so aphids within a few minutes. I was thrilled to actually capture this in such difficult photographic circumstances!

Interestingly, parasitised aphids do not leave the plant, but continue feeding. The egg hatches and the wasp larva gradually consumes the aphid, eating non-essential parts like the sexual organs first. This also stops the aphid reproducing. Braconid wasps can be cultivated for use a "natural" controls for aphid infestation.

Comments

Photo comment By Africa Gomez: Wow, excellent observation and capture!

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