Friday 24 April 2015

Look at what else I saw yesterday

Yes, I do have a fascination for Orange Tip butterfly eggs. A few thoughts. Each butterfly lays hundreds of eggs and are selective about where they lay them. That's simply because the caterpillar needs to emerge from the egg very close to its food source to have any chance of survival (it's first food is usually the egg casing but that's just a starter). A first thought is, why with so many eggs being laid isn't finding them easier? Well, concealment is probably important to survival and particularly where the development from egg to adult is so complex as with the butterfly.

Yesterday I noticed an Orange Tip by the entrance to Rowley Fields at the top of Blue Cap Road. There was a large Garlic Mustard plant right by the gate just inside the field. Although I hadn't found an egg on this before, the other favoured food plant, I  took a look and there was the tiny orange egg. All this stuff going on and most of the time we don't notice. Once you start looking and have some success then it can be good fun.

The chances are that this one won't survive but the clever butterfly will be mitigating the risk of not passing on its genes by laying many eggs on many plants. I'll keep an eye on it over the coming weeks.

As a general rule in nature the more potential offspring through seeds, eggs for a particular species, the less likely each one is to survive into adulthood to pass on their genes. For example, if every single spore of a giant puffball fungus became an adult we would be knee-deep in giant puffballs. Same for horse chestnuts. Primates on the other hand tend to have just one or two offspring at a time.

Yesterday I found a dead young blackbird chick in the garden. It's harsh, but that's the way it goes. The blackbirds will lay several eggs and even have more than one brood a season. A bit like butterflies in some ways.


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