Wednesday, 14 July 2010

It's all interrelated

It's a bit early in the year for the fungal part of my brain to kick into action, but occasional summer specimens can stimulate the old grey matter.

This is Panaeolus ater, which is 'hygrophanous': it changes colour according to whether it is wet or dry. The dry weather has put it into this (very) dry state:

Panaeolus species are relatively easy to identify to family due to the mottled gills:

The larvae of many fly species eat the mushroom fruit-bodies, often consuming them to destruction, and you can be sure that if there are fly larvae around, then an ichneumonid won't be far behind them. This minute one was prospecting the outside of the caps, so I suppose it can detect them from there without having to go down and search each gill individually.
The timing of this parasitisation is critical: the mushroom fruitbody will only be there for a few days during which the fly larva must progress from egg to pupation. So the ichneumonid must locate the fly larva (and the mushroom!) during that very short time. That's at least a quadruple dependency: the ichneumonid depends on the fly larva which depends on the mushroom which depends on its host (usually a plant, dung or wood). And, of course, the host will have its own set of criteria for being there....

Staying with ichneumonids, this one is very numerous at the moment as it runs over and under leaves looking for caterpillars:


Gill said...

Fantastic shot of that (second) ichneumonid.

It is incredible that they search their 'prey' out in time to complete the life-cycle. I wonder if fly-infested mushrooms smell different from 'clean' ones so the wasps can smell them out from a distance? (Certainly when they are badly infested they can smell rancid, even to a human's relatively insensitive nose!)

Stuart said...

I rather think the mushroom has to be detected from distance and then inspected for hosts in close-up fashion. Considering the lack of fungi at the moment, the ichneumonid must be able to detect them from very long range.

The timing issue gets much more interesting the more you look at it. Some fly larvae take weeks to mature (the ones inside composite florets, for example). Others, such as the mycetophilids, have to reach maturity before the fungal caps are dead, which is just a few days. Both sets are parasitised by (very different) ichneumonids.

Clare said...

Gosh, Dawros Head, Portnoo, is covered in fairy rings.