Hairstreak pupa predation

[Padfield]

I took this first photo on Saturday morning, not seeing the second shield bug hidden behind the white-letter hairstreak pupa. I didn't see the shield bug as a threat - I just thought it would make a good picture.



When I revisited today, the truth became clear.











I think the white spots on the pupa are where bugs have fed and I conclude there is no chance of saving it - it is probably already dead. Can anyone confirm this bleak picture?

Guy

[Trev Sawyer]

Hi Guy,
I had never really though about Shield bugs being predatory - I sort of assumed they were all solely plant feeders, but with their needle-sharp mouthparts, I suppose a juicy pupa or caterpillar is an ideal meal. In your 3rd and 5th photos, you can actually see the deed being done. Once there is a hole on the pupa, the bacteria carried by the shield bug will help to digest it too, so I'm sure there is no way back for this one - looks like it has been riddled with holes too.
Not sure what the situation is in Switzerland, but apparently in the UK the only really predatory Shield Bug family is the Amyoteinae - this includes Picromerus bidens and Troilus luridis (which look similar to your insect), which generally eat caterpillars and beetle larvae. You would think that a tough pupa would be immune to most predatory attacks by insects, but obviously not when they have such weaponry.

Trev

[Padfield]

Thanks for the reply, Trev. While I was looking for WLH pupae I saw these shield bugs quite commonly on the elm leaves, quite possibly doing just the same thing I was (i.e., looking for WLHs). It wouldn't surprise me to learn they fed on the caterpillars too, particularly as the number of caterpillars seemed to diminish continually during June, without their being replaced by pupae. I did wonder where they were all going.

I saw an adult WLH in my garden a couple of days ago, so some have obviously made it through. But it is amazing the thousands of hazards that face a butterfly from egg to adult. I believe that to keep a population of butterflies stable roughly 1% of eggs laid must make it through to reproductive adulthood (more specifically, one male and one female out of every 200 eggs laid). That, of course, means 99% of eggs laid never make it. On my local brown hairstreak patch, about 50% of the eggs I found hatched. To whittle that down to 1%, it means 98% of those larvae get taken by disease, parasites, predators &c. before they emerge triumphant in the flight season.

It makes you think, when you see a butterfly casually flying around, doesn't it?

Guy

[Trev Sawyer]

Mmmm... and it's obviously no good trying to hide yourself in the leaf-litter or just sub-surface either (a la Brown Hairstreak pupae) - Even ants are no match for a hungry shrew: In his book "The Butterflies of Britain and Ireland", Jeremy Thomas explains how these small mammals search the pupae out, squeal with delight and rub their hands together with excitement at each one they find. I suppose they are the shrews' equivalent of truffles!

Trev

[Piers]

Amazing series of pics Guy, that's fascinating to see. If you look closely at the first image, a second Shield Bug is already at the pupa.

It's not "bleak" though; surely just really interesting. Butterflies are just part of the food chain...!

(I could easily get into the heteroptera....)

Felix.

[Padfield]

It's not "bleak" though; surely just really interesting.

It's not bleak unless either:

a) you happen to be that particular white letter hairstreak,

or

b) you still remember the stormy night the caterpillar pupated and were rather hoping to get video footage of it popping out into the sun some time in early July.

My grief was a little alleviated today when a magnificent poplar admiral circled me, flew off, flew back at me and then eased over the trees (probably in a different country by now - those butterflies can really fly!!), bringing my year total to 150 species. Just 50 to go to reach my target for 2010 - and I haven't begun on the mountain season yet, so it should be easy...

Guy

EDIT : I've just written up my diary and it only comes to 149 species. I think I counted one butterfly I was hoping to see, but didn't.

[Piers]

It's not bleak unless either:

a) you happen to be that particular white letter hairstreak

Come on Guy, the pupa can not experience 'bleakness'. or any other human emotion for that matter...

b) you still remember the stormy night the caterpillar pupated and were rather hoping to get video footage of it popping out into the sun some time in early July.

Yeah that's a bit of a bummer, but look on the bright side: you captured the bug footage; and that, arguably, is far more interesting...!

Felix.

[Padfield]

My dear Felix, in your crusading zeal to purify and rationalise the scientific study of butterflies you are forgetting the richness and subtlety of the English language!! The outlook can be bleak for a listed building, a summer, a romance or a scientific theory, none of which things can experience human emotion. It can look bleak for a chrysalis too. Leave us the poetry...

You know perfectly well I never attribute human emotions to beasts. I attribute bestial emotions to humans.

Guy

[Piers]

Leave us the poetry...

You gouged my mind’s eye,
Tantalised all inner thought,
Shocked from unknown angles;
Sold me, told me cold,
Unfolded, moulded;
Shouldered any harbouring
Of empty morals.

You spun me round; undressed –
Pestered me with background riddle –
Piffle came to gleaning meaning.
And you stripped out prejudice – for none
Must exist in poetry,
Lest you close up an open mind
And **** up as reader;
Lest your heart is not a bleeder –
It has to be – let it flush out
Upon your sleeve.

You lay apart my thinking brain
And let in the literary pickings of a
Great poetic phallus.
Yes, poetry can be callous.

M.R.S. 2010

[Padfield]

[Cotswold Cockney]

Yes, Shield Bugs are predatory on the earlier stages of butterflies and other insects. In the field, I have sometimes found a Shield Bug ( also known as Stink Bug in the UK ) with its hypodermic like proboscis into a larva of a Small Tortoiseshell in the colony webb. Safety in numbers but, not for that one individual larva. Not only that, when breeding Commas on potted elms over twenty years ago, I once found a Shield Bug inside my large greenhouse with its proboscis through the cage netting penetraing a newly formed Comma pupa. I also regularly checked the breeding cages at night when other predators are about. On that same large cage with suspended Comma pupae, I found a Wolf spider with both it's 'fangs' through the netting into another Comma pupa.

I'm a great believer in live and let live. However, even though I have no livestock to tend for years, whenever I see a shield Bug in my garden, I dispose of it. Conversely, I always let the many spiders there run free...

====================================================

P.S.

By the way, those potted Elms became Bonzai-ed over many years trained and kept to breeding cages sizes. Twenty years ago, I planted most of these Bonzai Elms in my little Nature Reserve. One or two soon grew into fairly large shrubs, now trees. Most only in the past year or so have quit there Bonzai forms, spreading their roots now an suddenly developing a large main upright limb and growing more substantially. One of the Elm species ( not sure which species ) was selected as possibly resistant to Elm Disease. It's now over twenty feet tall and I have struck several cuttings from it over the years which themselves are now quite tall young trees.

I also planted some Potted Celtis species ( Elm like members of the Ulmacae) in the field. I used to rear several species of Apaturinae from both Asia and N.America on Celtis. They do not like the soil in my field and although they are growing, it is a slow process for them there. Quite unlike the Celtis sinensis in my garden which after only a few years, grew into a substantial tree ~ obviously the soil suited it better unlike those of the same species planted in the field. Some of the planet's finest members of the worldwide "Purple Emperor" family use Celtis as larval foodplant, including one of the largest such as Saskia Charonda ( The Great Purple Emperor Japan's National Butterfly ) and from mainland China, the even larger Sasakia funebris which in adult form, is mainly Black, with some white and red where it mimics poisonous Asian Swallowtail species. Their larvae are handsome beasts ~ here's digital images of prints I took when I bred them back in the 1980s.

Fully grown larva :~



Larva and Pupa :~



Newly emerged imagine and pupa on Celtis sinensis :~



P.P.S.

Elms... whilst visiting an aged relative in Gloucester Royal Hospital a couple of days ago. I was pleased to see the huge elm tree near the main entrance still thriving and healthy. There was another pleasing sight on that visit, two young Peregine Falcons exercising their wings and flying around the front of the main building, which their parents have used for a number of years to rear their young on the tall cliff like front wall. The young Peregrines both took short flights from the top of their "Cliff" face, and were harried by two or three Herring Gulls each time. Fascinating to see this sort of event in the centre of a UK City...

I took a picture of the Elm. White Letter Hairstreaks I used to see in the very centre of the city whilst there were fine, mature Wych Elms in the nearby park ~ all long gone... but not this tree fortunately. It's a fine specimen ~ I wonder :~

[Padfield]

It did occur to me, CC, that the purple emperor vibration reaction you introduced me to would easily be sufficient to shake off a shield bug before it got its proboscis in. Of course, I will keep checking my emperor daily, and will gently move away any likely predators to a different bit of the wood; but landing on one of those pupae must be a bit like sitting unexpectedly on an electric fence.

Guy

[Cotswold Cockney]

It did occur to me, CC, that the purple emperor vibration reaction you introduced me to would easily be sufficient to shake off a shield bug before it got its proboscis in. Of course, I will keep checking my emperor daily, and will gently move away any likely predators to a different bit of the wood; but landing on one of those pupae must be a bit like sitting unexpectedly on an electric fence.

Guy

Yes, it would effectively shake the bug off. The Sasakia pupae in my pictures are about three times the volume of an A.iris pupa and thus much heavier. When they shake themselves as described their leaves and branches really vibrate and if the shaking was deployed very suddenly and vigourously, Shield Bugs and other potential enemies would be shaken loose well before they could take a firmer grip and hold on.

Looking again at your "Bug" pictures, on the fourth one down there appears to be a freshly emerged parasitical fly or wasp... note pale colouring. Not also the colour of the w-album pupa. Black not warm brown as in a healthy pupa. I suspect the unfortunate pupa was parasitised in the larval state and the shield Bug is sucking the bodily fluids of the parasites still within the pupa. A case of parasites being parasitised.

Mother Nature is a funny old girl and moves in very mysterious ways sometimes... Like most women, usually has the final say ....
..

[Piers]

Looking again at your "Bug" pictures, on the fourth one down there appears to be a freshly emerged parasitical fly or wasp... note pale colouring.

Not so; it's a fly of the genus... (the name escapes me...shall look it up later...) which would have been attracted by the already pungent smell of the dead (decaying) pupa. This is not a parasitic fly; more an oportunist that is already staking it's claim on the next stage in this particular pupa's aproximated role in the grand scheme.

Felix.

Ps. There are still some fine mature Cornish Elms growing down in the far south west in 'God's Country'...

[Cotswold Cockney]

Looking again at your "Bug" pictures, on the fourth one down there appears to be a freshly emerged parasitical fly or wasp... note pale colouring.

Not so; it's a fly of the genus... (the name escapes me...shall look it up later...) which would have been attracted by the already pungent smell of the dead (decaying) pupa. This is not a parasitic fly; more an oportunist that is already staking it's claim on the next stage in this particular pupa's aproximated role in the grand scheme.

Felix.

Ps. There are still some fine mature Cornish Elms growing down in the far south west in 'God's Country'...

Is that fine tree in my picture a Cornish elm? Can you tell ? It's leaves are not as coarse as those of Wych and English Elms... I suspected it to be a Cornish Elm, like some of those I've grown from cuttings in my field" reserve". The leaves of my plants and that fine tree look identical.

You could well be right there. However, that fly in the picture is very small ~ compare it to the size of the pupa ~ itself quite small. The bug looks huge but they are not very big. I have seen fly/wasp like that pale one emerge from wild collected larvae or pupae which after a while, lost that pale colouring and became generally much darker. I have also had what appears to be a harmless house fly emerge from an Apatura pupa. I later discovered it was a Tachinid species and they lay disproportinately large banana shaped eggs on the backs of larvae. I used forcepts to carefully remove those eggs which are attached with one of the strongest adhesives in the known universe...... so strong that it's almost impossible to remove them from the larva's back so I usually crush the eggs....seen the female flies about my greenhouse and thought nothing of it until I observed one actually attach an egg to a larva's back. This was many years ago and someone from Oxford Scientific films phoned me out of the blue soon after with an unusual request. They were doing a film project on flies and would like to know if I knew anything about Tachinid flies and if I could obtain some for them. He was amazed when I told him that not only did I know what flies he was talking about, but I could provide a few living specimens for the project ~ he was delighted...
..

[geniculata]

hi guy,


the bug in your picture looks like the final instar nymph of pentatoma rufipes, the forest bug, which is noted for attacking other insects.
another picromerus bidens, which is noted for targeting butterfly and moth larvae and pupa, i posted a pic of last year sucking dry a small copper caterpiller, found on a walk in the new forest. find image attached

gary

[Lee Hurrell]

I used to quite like Shield Bugs....

[geniculata]

bare up lee!,

just remember everything has its place in the order of things!

gary.

[Lee Hurrell]

Yeah I know that really Gary...but it is amazing what the immature stages have to go through (or avoid more likely!) to get to adult life eh?

Cheers

Lee

[geniculata]

yep!

certainly is a numbers game.

gary.