Tuesday, 26 July 2011

Bug babies leave their siblings

After at least ten days clustering together on top of their egg cases, the 28 Green Shield Bugs, Palomena prasina, nymphs finally left their siblings after moulting into a greener instar. This is the sequence of events:
12/7/11
13/07/11
20/07/11 All have now moulted into the greener 2nd instar
22/07/11. The nymphs start to disperse in the morning.
22/07/11. After an hour, only three reluctant nymphs remain on the egg cases. In the evening they had all dispersed. 
Some of the adventurous nymphs. I found one a meter away from the egg cases.

8 comments:

damselfly said...

I just found your blog and I was very impressed by the crispy photos you posted. How do you take photos of the small objects like insects? I always blame my equipment :)

Blackbird said...

Welcome to BugBlog damselfly and thank you for your comments. I use a portable Canon Powershot G10 and crop the photos quite a bit. I get as close at possible and move the focus point to avoid the flash shade. Sometimes I use a white paper as diffuser, but not for the bug shots in this post. Keep visiting!

Ray said...

As ever there are a multiple of 7 eggs. It happens with many Shieldbugs, but with Palomena prasina I don't think I ever ever come across a count of other than 21 or 28 eggs.

A clutch I monitored last year emerged on 03 August and dispersed on 05 August. (eggs laid circa 23 July).
http://www.flickr.com/photos/fence_s13/sets/72157626193738700/detail/

Blackbird said...

Hi Ray, thank you for commenting. I never knew that, always multiples of 7. I must check on other photo I have of a clutch. Do you know if they feed before dispersing?

Ray said...

Almost always :)
I did find a batch of 30 Dolycoris baccarum (Hairy Shieldbug) eggs this year.

Amongst shiledbugs that disperse widely directly from the egg cases, I've seen no evidence of prior feeding on the plant leaf, but I did once read something that said the grazed on the egg cases - and ingested a chemical it contained.
(I'll try and dig up that paper...).
Some shieldbugs, Eysarcoris venustissimus for example, appear to stay on the same plant as their egg cases - laid on Hedge Woundwort - their foodplant, through early instar stages .

From what I have seen of the predatory shieldbugs T. luridus and P. bidens, they leave the egg cases quickly but continue to stay as a (hunting?) pack through their early instar stages.

Ray said...

A quick search only brings up these unreferenced anechdotal statements relating to the eating of the egg-cases:
http://bit.ly/fF47iA

... with Colin Duke using exactly the same words here:
http://bit.ly/pcMOGW


Perhaps I should dig deeper :)

______________________________

If you can get behind the paywall on this:
http://bit.ly/pxSkFx
it could be of interest.
(Development of eggs of 35 species of Nearctic and Palearctic Pentatomoidea are described ..)

Blackbird said...

Thanks a lot for the info Ray. I have a post due on Eysarcoris, I have naturalised hedge woundwort in the garden, and they also like Lambs ears. I cannot go through the paywall, but this thing of them obtaining endosymbionts from the egg shells is very interesting.

Ray said...

"I have a post due on Eysarcoris, I have naturalised hedge woundwort in the garden, and they also like Lambs ears."
I look forward to your post - they are always very interesting.

I hadn't been aware of Lambs ear connection, I've only ever seen them on Hedge Woundwort. In my garden, the final pair of adults disappeared about a week ago, leaving one clutch of eggs (in a calix, rather than on the underside of a sepal).
There are quite a few early/mid instars from earlier hatchings still feeding on the seeds.

* I also find Hairy Shieldbug eggs and instars on the Woundwort.
_____
I'm still working on the first instar feeding question. Anecdotally I read that they do feed and that even the predator Sbs are "plant eaters" at first instar stage. ... but we still have so much to learn about all these guys.