7-Spot Ladybird behaviour

Malcolm Fraser · #1 (**permalink**) 20-07-2009, 02:15 PM

Hello,

I was surveying a small patch of green roof today and found a large number of 7-spots, larvae and pupae on the concrete 'kerb' and adjacent pebbled area which borders the green roof.

I don't really know anything about ladybird behaviour so I'm wondering why they should choose this sort of place to pupate/forage.

Do they tend to pupate on rock surfaces etc? Is this to absorb heat from the rock? And why would the larvae be foraging in pebbled areas? I didn't see any other smaller insects in and around the pebbles, so maybe they were foraging on the green roof and then moving to the pebbled areas?

Any help would be appreciated.

Thanks!

Malcolm Fraser

Paul mabbott · #2 (**permalink**) 20-07-2009, 04:03 PM

I've seen more or less everything but this is very uncommon behaviour for 7-spots but very common for Harmonia axyridis, the 'harlequin ladybird'. So, the first thing I would do would be to re-examine the pupae - do they have the 'crown of thorns' at their attached end?
I have a theory why they do this - pupating on gravestones, traffic signs, walls any flat, non-biological surface: pupae or larvae that are attempting to pupate are very susceptible to attack by larvae and other predators; however, such predators are likely to concentrate on biological surfaces (foliage, trunks &c) so the final instar larvae go elsewhere to pupate!
I presume the same would apply to 7-spots?

Dogghound · #3 (**permalink**) 20-07-2009, 05:55 PM

Also tiles and stone absorb heat better than plants and wood so the pupa will develop more quickly.

Malcolm Fraser · #4 (**permalink**) 21-07-2009, 05:32 PM

Here's a few photos just to double-check I have the right species, could someone confirm they are all 7-Spot Ladybirds?

Let me know if the images are too small.

Thanks!

Acutipuerilis · #5 (**permalink**) 21-07-2009, 06:09 PM

I've been seeing exactly the same in Leeds - they all come off the solitary lime tree, and pupate on the nearby concrete wall - and yes, they're dominantly 7-spots. The wall is in shadow most of the time, so I don't think it can be the heat effect.

At our other museum, with no handy wall nearby, they're flocking to the fence posts instead.