PARASITC WASPS AND MOTHS.

With more than 5,500 species of parasitic wasps in Britain, many of which play a significant role in the life cycles of moths and butterflies, I thought it only right to devote an entire post to them. Many have life cycles more fascinating, complex and bizarre than their hosts, but despite this, they remain a very under studied group of insects with a very large majority of species having nothing known about their host associations.

Below is a sample of some of the encounters I’ve had with them during my few years of rearing moths.

ECTOPARASITOIDS AND A LIGHT BROWN APPLE MOTH LARVA.
Aug 7th 08.Parasitoids differ from parasites in that they feed on the host, eventually killing it where as parasites rarely do so. Ectoparasitoids feed on the outside of the host where as endoparasitoids feed internally. Here the moth larva has become discoloured where the wasp larvae are feeding.

A day later and the larvae have greatly increased in size.Usually they keep the host alive as long as possible by feeding on none essential tissue like body fat and reproductive organs.

Another 24 hours on and the moth larva is nothing more than a discarded shell. Havimg fed up seven of the larvae have already pupated in whitish cocoons with two more looking to so.

13 days later and the twitching of antennae herald the emergence of the adult wasp.

This wasp has subsequently been ID-ed by Mark Shaw as an Oncophanes species, presumably minuta. 

ANOTHER ECTOPARASITOID - PNIGALIO SOEMIUS AND ECTOEDEMIA SEPTEMBRELLA LARVA.

Clockwise:
1. Day one - Aug.5th 2012. The mine on cultivated hypericum found just a couple of gardens away.
2. The moth larva with two ectoparasitoids gently sucking the life out of it.
3. Day four and one of the parasitoids has "disappeared" whilst the other has grown enormously.The host is little more than an empty skin.
4. Day eight and the fully fed larva is a translucent bag of waste products.

5. Day nine and the gut has been emptied with an unordinate amount waste matter strewn about.
6. Amazingly, two days later and a jet black pupa emerges from the white pre-pupal larva.
7. Eight days after pupating the the wasp emerges leaving behind the empty pupal case.
8. The adult chalcid wasp - Pnigalio soemius with a body length of 2mm. Thanks to Dick Askew for identifying the wasp which will be sent off to him to so he can place it in the appropriate reference collection.

AN ENDO/ECTOPARASITOID AND AGONOPTERIX HERACLIANA.
June 19th 2010. The Agonopterix heracliana larva (lower) was found spun up on Hogweed at Long wood. The braconid wasp larva (top) had been feeding internally up until now but as the moth larva nears pupation (it begins to take on a pinkish tint) the larva exits its host and finishes off by feeding externally.Thanks again to Mark Shaw for this fascinating insight.

Just over 5 hours later and the moth larva is reduced to nothing more than a head capsule and skin - the wasp larva is ready to pupate.

By the next morning a cocoon had been spun and pupation is on the way. Obviously not fussy about a particular site to pupate in it has spun up on the spot with the moth larva remains close by.

Just four days later and this adult wasp appeared. Subsequent information has come to light indicating that the wasp illustrated should have emerged from a moth pupa and taken much longer than the four days stated, also it is from the wrong family associated with initial wasp larva. This means that it has almost certainly emerged from an unseen moth pupa in the rearing jar - perhaps from a larva that pupated between two layers of tissue paper.

PHYLLONORYCTER OXYACANTHAE AND WASP PUPAE.
Feb.23rd 2010.A Phyllonorycter oxyacanthae mine on Hawthorn found at New Lane the previous Autumn. The opened mine contains not one but three parasitic wasp pupae. I normally expect no more than one per mine at most so three was quite unusual.

Feb.27th 2010.The three wasp pupae removed from their mine to be reared through along side four oxyacanthae pupae from other mines. Not surprisingly with three wasp larvae to one host they are considerably smaller.

Mar.17th 2010.One of the newly emerged adult wasps. It's the chalcid wasp - Achrysocharoides atys. At 1.4mm long this is the smallest insect I've attempted to photograph and so I make no apologies for the less than perfect photo.
-------------------------------------------------------------------------------------------------------------
MISCELLANEOUS.
 A phyllonorycter pupal case in a mine on Sallow, Mar.7th 2010 collected the previous autumn. Not only has this parasitic wasp larva fed inside the pupal case but it has pupated inside it as well. The basic features of the pupa can be made out as well as the frass pile.The adult wasp, Pediobius saulius emerged 15 days later and is illustrated below.
----------------------------------------------------------------------------------------------------------------------------------

A selection of parasitic wasps reared from leaf mining moths. Clockwise from top left:

Sympiesis sericeicornis (male) from a Phyllonorycter quercifoliella mine on oak.
Pnigalio pectinicornis (male) from a Tischeria ekebladella mine on oak.
Pediobius saulius from a phyllonorycter mine on Sallow.
A chalcid wasp - family Eulophidae from a Stigmella aurella mine on bramble.

All beautiful and fascinating insects in their own right. Many thanks to Dr. Dick Askew for his invaluable help in identifying these wasps.
----------------------------------------------------------------------------------------------------------------------------------

Hyperparasitoid larva, Apr.12th 2010. This is an opened mine of what I presume was made by the moth Phyllonorycter quercifoliella on oak. The moth larva or pupa has been eaten by a parasitic wasp larva which had then gone on to pupate - the remains of which is dark object in the photo. This in turn has been "stung" by a secondary parasitic wasp or hyperparasitoid which specialise in feeding on other parasitic wasp larvae/pupae. The featureless larva can been seen within the original wasp's pupal case. This is the only evidence I have found so far of hyperparasitism.
---------------------------------------------------------------------------------------------------------------------------------

May 10th 2011: This Dun-bar larva has been eaten by what I believe is the larva of the ichneumon wasp Scirtetes robustus. It has then gone on to pupate in this neat little egg-shaped cocoon.
--------------------------------------------------------------------------------------------------------------------------------

May 19th 2012: Caught in the act. This parasitic wasp larva was observed breaking out of a much prized Bucculatrix nigricomella larva.

The larva emitting an inky black liquid - perhaps emptying its gut contents as moth larvae do prior to pupation.

Pupation successful and the typically frail, exarate pupal case seems nothing more than a transparent second skin the day before emergence.

And finally the adult has emerged. It's probably Diadegma pusio, a male, which is one of two species of Diadegma that parasitises Buccalatrix species. Thanks to Mark Shaw for his comments on this wasp. He also says the blobs in the abdomen are probably uric acid (waste products) rather than eggs which is what I thought they might be.
----------------------------------------------------------------------------------------------------------------------

This Coleophora case was found in North Dean wood on Apr.3rd 09. It appears to have been parasitised and the adult wasp has chewed an untidy exit hole, whereas the moth would have exited at the rear opening leaving no trace of its emergence.
---------------------------------------------------------------------------------------------------------------------------------

7-Spot Ladybird, Skicroat Green allotments, summer 07.
Not moths but along the same lines. This ladybird has been parasitised by the braconid wasp Perilitus coccinellae and to explain exactly what has happened I've taken this extract from Chris Rapers web page.

"The wasp stalks a suitable ladybird before thrusting its ovipositor between the host's abdominal plates and laying a single egg inside. When the egg hatches the first job for the larva is to eliminate any competition. It is equipped with large, pointed mandibles and it uses these to stab other parasitoid eggs and larvae. Soon after this is will shed its skin revealing mouthparts suitable for eating the host. During development the larva takes very great care not to eat any of the ladybird's vital organs - in fact it seems to limit itself to the ladybird's fat store and gonads. When it is ready to pupate, it uses its mandibles to cut each of the six motor-neurones that control movement in the ladybird's legs before breaking out of the host's abdomen and spins a cocoon between the host's legs. This may seem strange behaviour but the wasp actually wants the ladybird to stand sentry over the cocoon. The ladybird can't move but it is still alive so the bright warning colours and reflex bleeding that once protected the ladybird from predators will now protect the wasp. Eventually the wasp hatches and flies off to find another ladybird leaving the host to starve".

2 comments:

rusticus said...

Excellent photos again Charlie.

Did you send the Sirtetes robustus record to Bill Ely (YNU Recorder)?

Has the adult emerged yet? I have a pupa over-wintering in the garden.

Derek

charlie streets said...

Hi Derek,good to hear from you again.I tentatively ID-ed it as S.robustus from a post on your blog if memory serves me correctly so I could be wrong - it just looked a good match bearing in mind the host.Much as I like parasitica I don't often have the time or enthusiasm to rear them through so this one was binned pretty quickly!