It's edible, although it tends to take on the flavour of other cooking ingredients, rather than adding flavour of its own.The other day I mused about dependent species following their host. This concept is very clearly illustrated by Apanteles glomeratus, a Braconid wasp that is parasitic on some of the 'white' butterflies. The Large White and Small White butterflies became very scarce on my local patch, presumably because people had stopped growing their own brassicas: the Large White wasn't recorded in our 10k square for 10 years. However, as soon as I started growing Broccoli 2 years ago, both species were recorded on my vegetable patch.
When they're ready to pupate, they crawl up to the eaves of buildings and overwinter in their chrysalis. They start by making a web on the upper surface, and this is the instant that disaster can strike. The larvae of Apanteles glomeratus live inside the caterpillar, eating non-essential fat deposits, using the caterpillar as a mobile food producer. The instant the web is spun, however, they burst through the larval skin and pupate for themselves. The yellow cocoons are shown below:
Approximately 60% of this year's Large White larvae appear to be parasitised, which falls within normal expectations.
So although the host was missing for 10 years, the parasite is present only two years after the host returned.
6 comments:
So if the parasitic larvae only eat the fat deposits in the caterpillar, does it (the caterpillar) survive to pupate and emerge?
Or do the braconids emerge first and then re-parasitise the butterfly pupa or adult?
Makes you wonder where the parasites were hiding all those years there weren't many white butterflies....
>So if the parasitic larvae only eat the fat deposits in the caterpillar, does it (the caterpillar) survive to pupate and emerge?
No. It's quite dead. The fat deposits aren't required by the caterpillar, but they would be essential for the pupation to succeed.
>Or do the braconids emerge first and then re-parasitise the butterfly pupa or adult?
There are a few parasitic wasps that parasitise adults of insects (and spiders), but the vast majority only parasitise larvae.
>Makes you wonder where the parasites were hiding all those years there weren't many white butterflies....
One of the things I notice about the Campodorus is that they clearly navigate by plant type. The wasps land on the tree and then seek larvae, rather than flying directly to the host. Various studies postulate that the parasitoids navigate firstly by habitat/environmental features, then by plant, finally seeking the host.
So I suspect the wasps flew in from further afield, presumably attracted by my broccoli. (I also suspect the butterflies weren't actually missing from my patch but were simply present but unrecorded.)
Fascinating - so presumably the braconids (and maybe the butterflies too) are navigating by smell, picking up chemical cues from the target plants?
Surprising to think no residents in your 10k square would grow Nasturtium's for 10 years, another of the brassica species very much a favourite by both humans and White's.
In fact, the record that broke the 10 year drought was found on Nasturtium.
It should be noted that the flower called Nasturtium belongs to the Tropaeolum genus and should not be confused the the genus Nasturtium which is, indeed, a brassica.
"It should be noted that the flower called Nasturtium belongs to the Tropaeolum genus and should not be confused the the genus Nasturtium which is, indeed, a brassica."
Quite so, but I believe it produces some of the same chemicals (the sharp, mustardy smell and taste) which is what attracts the 'cabbage' white butterflies.
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