Wasp Predation on Caterpillars ???

[Perseus]

Hello,

14 June 2009
Privet was flowering in profusion and intruding on the lower slopes of Mill Hill in a damaging way (damaging to the long term prospects of the butterflies).

Another noteworthy observation was a nest of the Common Wasp, Vespula vulgaris, in a small hole and scores of wasps were seen entering and leaving in a few minutes, until I felt it was too dangerous to stay around. I debated about the significance of such a large congregation of predators on the caterpillars of the butterflies?

Butterflies on Mill Hill have deteriorated in the last two years dramatically. I wonder if the presence of five thousand or so wasps could be partly the reason?

Mill Hill Reports 2009
http://www.glaucus.org.uk/MillHill2009.html

Adur Butterfly & Large Moth List
http://www.glaucus.org.uk/Butterfly-list2009.html

Cheers

Andy Horton
glaucus@hotmail.com
Adur Valley Nature Notes
http://www.glaucus.org.uk/Adur2009.html
http://www.glaucus.org.uk/Adur2008.html
Adur Valley Nature Notes: June 2009
http://www.glaucus.org.uk/June2009.html

[Perseus]

Hello,

Does anybody have any papers on wasp predation on caterpillars please?

On Mill Hill there has been a dramatic decline of the Chalkhill Blue Butteflies in the last two years since the wasp nests were discovered. On the first occasion when they attacked and stung me repeatedly !

Mill Hill Reports 2009
http://www.glaucus.org.uk/MillHill2009.html


Cheers

Andy Horton
glaucus@hotmail.com
Adur Valley Nature Notes
http://www.glaucus.org.uk/Adur2009.html
http://www.glaucus.org.uk/Adur2008.html
Adur Valley Nature Notes: June 2009
http://www.glaucus.org.uk/June2009.html

[Dave McCormick]

Hi Andy, I looked around for links and found these if any helps:

http://www.nature.com/nature/journal/v4 ... 3704a.html

This might be more what your looking for: http://www.learnaboutbutterflies.com/En ... rflies.htm

[Zonda]

I nearly always have a wasps nest in my pocket handkerchief wildlife garden. I think that keeping the wasps to one nest is beneficial for the natural environment, and for the vegetable garden. I don't think that predation will be a problem with one nest. It certainly does not affect my butterfly population.

[Dave McCormick]

Well, Small Brachnoid wasps can find large white caterpillars easily. When the caterpillars feed on cabbage leaves, the leaves produce a smell that attracts the wasps, see images taken in my garden:

young caterpillars feeding away on Brussels sprouts leaves:


Wasp (apanteles glomeratus) comes looking for caterpillars:


Wasp (apanteles glomeratus) finds the caterpillars:


After the wasps find the caterpillars, they will lay an egg or more than one in the caterpillar and move on. The caterpillar will continue to feed, unaware that anything happened. It takes a while, but the grub of the wasp eats what the caterpillar eats and when the caterpillar grows fully grown, when its ready to pupate, instead, yellow cocoons pop out of the caterpillar. These are the grubs that were in the caterpillar. The caterpillar now dies and the wasps form in cocoons and burst out as adult wasps. Here is the cocoons on a large white caterpillar at BallyMcormack point, Co Down, Northern Ireland:



This is why Large whites lay so many eggs, many don't make to adult, but enough do to carry on their kind.

[NickB]

Nice sequence Dave
..also makes you wonder at exactly how and how long these relationships have become established?
As you say, the wasp does not want to wipe out the population - that is a stupid parasite - and the butterfly understands that only a certain percentage of their offspring will survive to adulthood and lays sufficient eggs to compensate. It seems that it is only something like man that can disrupt this natural equilibrium to the detriment of both species, sadly.
N

[Dave McCormick]

Well it works both ways. During years where there is a lot of a butterfly species, say Holly Blue (like last year), there will be predators on their caterpillars early on, then there will be more predators around because of the increase number of caterpillars to parasite on, then the numbers of Holly Blue fall, not enough to destroy a population completly usually, but enough that the butterflies continue to survive and carry on. The wasps then start disappearing too. With the less caterpillars to parasite and feed on, the less predators to get the caterpillars and the caterpillars have more of a chance to survive so more appear and the cycle begins again. If there is nothing else (like natural disasters, abnormal weather, man etc...) to disturb the butterfly/wasps cycle, it should continue on like this.

The large whites lay many eggs because their caterpillars are not poisionous or camoflagued well to leaves they eat, unlike others like Small white which has green caterpillars which are camoflagued to leaves they eat and Orange-Tip caterpillars which are distasteful based on what they eat and so on.

[xmilehigh]

Here's another link to a study that was undertaken in New Zealand on the prey items of the Common Wasp, Vespula vulgaris. It seems from the table on page 7 that butterfly larvae is a major part of it's diet . So some pure speculation on my part would be that a nest with many hundreds or thousands of wasps could have an impact on butterfly populations in the vicinity, especially if the wasp had not been present in the area before.

http://www.nzes.org.nz/nzje/free_issues ... 17_1_5.pdf

Hmmmmm

[Perseus]

Here's another link to a study that was undertaken in New Zealand on the prey items of the Common Wasp, Vespula vulgaris. It seems from the table on page 7 that butterfly larvae is a major part of it's diet . So some pure speculation on my part would be that a nest with many hundreds or thousands of wasps could have an impact on butterfly populations in the vicinity, especially if the wasp had not been present in the area before.

http://www.nzes.org.nz/nzje/free_issues ... 17_1_5.pdf

Hmmmmm

This was my intuition as well. I think it is probably wrong. Although the Chalkhill Blue populations on Mill Hill, Old Shoreham, have collpased since I spotted the wasp's nests and there has been no other crucial managment changes, a fall from 750 an acre in 2003 to 50 an acre in 2009 is a rapid decrease. The Adonis Blue populations have not shown the same fall.

[Piers]

Hi Perseus,

There are two aspects to your wasp predation theory that don't necessarily hold water; namely that coridon larvae are nocturnal and tend to hide during daylight (wasp hunting) hours. Also, by the time that a wasp nest is maturing and wasp predation reaches significant levels the coridon larvae will have pupated.

The most likely cause for the decline in numbers on your site is a decade or so of unfavourable (for coridon) weather; mild winters and warm wet springs. Coridon ova are susceptible to predation during mild winters, by invertebrates that would not be active (or even alive) during a cold hard 'English' winter. There is also the possibility that mild wet winters cause a significant proportion of the ova to fail.

Mild damp springs cause the vegetation on some sites to grow and develop at a rate that is far from favourable for coridon, the lush vegetation creating a microclimate that is unsuitable for larval development, resulting in a high mortality rate.

With regards,

Felix.

[Perseus]

Hi Perseus,

There are two aspects to your wasp predation theory that don't necessarily hold water; namely that coridon larvae are nocturnal and tend to hide during daylight (wasp hunting) hours. Also, by the time that a wasp nest is maturing and wasp predation reaches significant levels the coridon larvae will have pupated.

The most likely cause for the decline in numbers on your site is a decade or so of unfavourable (for coridon) weather; mild winters and warm wet springs. Coridon ova are susceptible to predation during mild winters, by invertebrates that would not be active (or even alive) during a cold hard 'English' winter. There is also the possibility that mild wet winters cause a significant proportion of the ova to fail.

Mild damp springs cause the vegetation on some sites to grow and develop at a rate that is far from favourable for coridon, the lush vegetation creating a microclimate that is unsuitable for larval development, resulting in a high mortality rate.

With regards,

Felix.

Hello,

Thanks for the reply. I had already rejected the wasp predation theory. The general climate is rejected as well because the fall of Chalkhill Blues has not occurred on other sites in Sussex.

The vegetation possibility is rejected as well. The site is too infertile and an explosion has not occurred on the lower slopes and if anything the Horseshoe Vetch has increased being the dominant flora. Waterlogging could occur as the chalk could clunch, but I don't think this is the reason either. I could make wild guesses but that is no help.




The 2003 figures was 750 an acre day count. The graph is ultra-conservative with numbers.

Chalkhill Blues

The maximum transect day count for 2008 was 81 on 30 July 2008, which was even lower than 2007 when the maximum 1.2 acre day count was 96 on 5 August 2007. In 2003, the Chalkhill Blues were too many to count and the estimate for the 1.2 acre transect was at least 375 and possibly double that.

Mill Hill Reports 2009
http://www.glaucus.org.uk/MillHill2009.html

Mill Hill and its Butterflies
http://www.glaucus.org.uk/MillHill2009Article.htm


First Adur Butterfly Dates 2003 to 2009
http://www.glaucus.org.uk/ButterfliesFFT.htm

Adur Butterfly & Large Moth List
http://www.glaucus.org.uk/Butterfly-list2009.html

Cheers

Andy Horton
glaucus@hotmail.com
Adur Valley Nature Notes
http://www.glaucus.org.uk/Adur2009.html
http://www.glaucus.org.uk/Adur2008.html
Adur Valley Nature Notes: August 2009
http://www.glaucus.org.uk/August2009.html