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I assumed they were Small White, Pieris rapae, because I had seen adults laying eggs although I couldn't be sure they weren't the caterpillars of Green-veined Whites, Pieris napi.
Later, once I saw the caterpillars were gone, I looked all over the walls of the house for chrysalises, but could only find one Small White chrysalis.
At the beginning of April this year I was sorting out the garden furniture in anticipation of a family visit when I notice a Small White chrysalis on the arm of a garden chair.
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Knowing that it wouldn't be safe I carefully removed it and placed it in a jar lined with paper towel inside one of my rearing cages.
About three weeks later I was checking the chrysalises and noticed a number of small insects climbing around on the walls of the cage. I realised that these were parasitic wasps and I found about 15 of them.
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When I checked the Small White chrysalis I noticed a neat round hole in it.
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I haven't been able to identify the wasps, but I am interested to know more about their life-cycle. I presume that they either lay their eggs into caterpillars or chrysalises and they must develop inside the chrysalis early in the spring. It was the 24th April when I found the wasps, a time of year when the Small White would be either still be chrysalises or would have emerged into adults. Any eggs the butterflies lay would only hatch in early June, about six weeks ahead. I wonder if there is another host that the wasp uses at that time of year.
Happily there have been a lot of Small White butterflies flying around this year, so a good number made it through without being parasitised.
It's impressive how parasitic wasps attack chrysalises. I've been reading, however, that some of these wasps are used as biological pest control to reduce populations of harmful insects in gardens and agricultural settings. There are so many different kinds.
ReplyDeleteHi Maria, I don't really know a lot about parasitic wasps and flies. I am not sure if each is specific to an individual butterfly. I am aware of various biological controls that are used, but I am always a bit concerned that if they are non-native they may start praying on a native species.
DeleteHello Nick :) It was lovely to see your comments. Interesting post, as I don't know anything about parasitic wasps, but now will look it up- I'm glad that some Small White butterflies did not suffer the indignity of being hosts. It's good to be back, although most of my time I keep indoors away from the heat. The forecast for the next few days is 38 degrees, so if you don't see me again, it's because I have melted!!
ReplyDeleteKeep well
Sonjia.
Hi Sonjia, I think I will need to find out more about parasitic wasps. There is so much I don't know. I couldn't find much on the internet. I hope that the hot weather doesn't last too long and I hope you don't melt!!
DeleteWe have parasitic wasps here on tomato hornworms. But, that is the most I know about them. I enjoyed this post and your photos.
ReplyDeleteI guess that in situations such as this the wasps are considered helpful in getting rid of garden pests, much like Maria has said above.
DeleteHi Nick :)
ReplyDeleteThank you for passing by my blog and leaving a kind comment. I try to keep a certain standard regarding my photography but sometimes it's just not possible, and like you, my other blog friends have left favourable comments which makes me feel better about the poor images. The saga of this particular woodpecker continues in my next post. It is cooler today and I hope it stays this way. Wasps have been coming regularly to drink water, and one day I saw one in the middle of the plate and I thought it had drowned, but although it stayed there a long time, to my surprise it suddenly flew away. It was only then that I realised that they need to drink and cool their bodies
just like us,
All the best
Sonjia.