Saturday, 28 April 2012

A bumper year for 7 spot parasites?

In the last few days I have found quite a few 7 spot ladybirds parasitized by the wasp Dinocampus coccinellae in the garden: live ladybirds snared to a silky cocoon underneath them. Today I did a quick count and found eight. You can see their portraits on this post. This is being a successful year for 7 spots: there are so many around it is hard not to get one or two ladybirds in the background of any bug photo I take! It is no surprise that ladybird parasites are enjoying this ladybird bonanza. If you want to find out more about the rather gruesome Dinocampus life cycle click here.
One on sage
on the conservatory frame
a second one on the spurge
one under a Lamb's Ears leaf
An odd one, with the cocoon on one side on a bougainvillea leaf in the conservatory
one on an orchid in the conservatory
a second one on sage

8 comments:

conall said...

This is fascinating! It looks like a really wonderful blog. I just took a similar photo today of a 7 spot with a cocoon under it and was wondering aboout it & a flickr contact directed me here.
It is a bit icky the way the ladybird twitches!
Anothe seven spot was mating with the zombie ladybird that i saw.
my picture is at:
http://www.flickr.com/photos/16176711@N02/6976006208/

Africa Gómez said...

Thank you conall! Yours is a very cool capture, I've never seen that myself. I read today females tend to be chosen by parasitic wasps, probably as they feed more and the wasp larvae are more successful in them. Male ladybirds won't be having much success mating with the parasitized females as they will die of starvation shortly after the wasp emerges.

Richard said...

The parasite has a preference for larger hosts (the larger the host, the more juicy innards it has!), so has a preference for females over males, and for larger species such as 7-spots. I found a 22-spot parasitised by Dinocampus last year - until the wasp larva emerged the abdomen was amazingly distended, as if it were full of eggs.

Theoretically the size/species of the host could in turn affect the size of the parasitoid - Lori's investigating, but I haven't heard any results so far

conall said...

Thanks Africa- fascinating stuff - amazing the wasp can identify and chose to oviposit in a female. I guess all the eggs in the ladybird are bound to be very high quality food for the wasp larva

Lori Handley said...

Wow, these area some of the best Dinocampus photos I've seen Africa. In response to Richard's comment, there is a positive correlation between host size and Dinocampus size within host species (at least for 7 spots). Also, smaller wasps seem to emerge from harlequins than 7-spots, consistent with the idea that harlequins are a marginal host, but we need more data from harlequins to test this more rigorously. So if any of your followers find any infected harlequins, we'd love to hear from them via the UK ladybird survey (www.ladybird-survey.org)!

Africa Gómez said...

Thank for your comments and info Richard and Lori. I was hoping to find some studies with correlations between ladybird population density and parasite prevalence but I found nothing. I keep watch on Pearson Parks harlequin population for parasites. Dozens were mating this week.

Richard said...

I also haven't found any studies between ladybird population size and parasitoids, despite much looking - the impression I get from the literature and my own work is that any linkage is very patchy and local-scale. Most of the parasitoids that attack ladybirds are not great dispersers (although Dinocampus is probably one of the better, being quite large), so landscape-scale effects would probably be beyond them.

As Lori mentions, we're very interested in any sightings of parasitoids, including the ladybird parasite survey - http://www.bbc.co.uk/breathingplaces/ladybird-parasites/ - which is more focused on the parasitoids which attack pupae

Ray said...

Hi
Have you come across this:
http://stippen.nl/dinocampus.php
?