Tag Archives: Celastrina argiolus

Holly blues, the second generation

22 Wednesday Aug 2018

Posted by in insects, nature

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I blogged about the Holly blue butterfly (Celastrina argiolus) back in May but I’ve since read some really interesting info about this lovely little butterfly and have some new photos to share as well.

180822 Holly blue (2)

My information comes from the book I’m currently reading, which I highly recommend – it’s Wonderland: A year of Britain’s wildlife day by day by Brett Westwood and Stephen Moss. The entry from 13 August is about the Holly blue and answered a query I had about why I’ve recently been seeing so many Holly blues on Ivy plants rather than on Holly.

180822 Holly blue female

It turns out the Holly blue has two generations per year: as their name suggests, the females from the first generation lay their eggs on Holly plants and that’s what the first generation of caterpillars munch on. Then, once those caterpillars have pupated, they emerge as butterflies from around mid July, and the females from that second generation lay their eggs on Ivy, as that’s what the second generation caterpillars eat.

180822 Holly blue (1)

I’ve also been wondering why I seem to be seeing so many more Holly blues this year and Wonderland has the answer to that too:

These fluctuations [in population], over a cycle of five or six years or so, are caused by a small parasitic wasp called Listrodomus, which injects the caterpillars with a long sting-like ovipositor. The Listrodomus grub lives inside the caterpillar, but keeps it alive long enough to allow it to pupate, emerging later from the chrysalis. As wasp populations increase, they reduce the Holly blues. Fewer butterflies mean fewer opportunities for the wasps and so, in turn, wasp numbers fall too. This allows the butterflies to build up again, and that’s why over a span of several years our sightings of Holly blues go up and down.

180822 Holly blue (3)

Fluttering butterflies, no.2

24 Friday Jun 2016

Posted by in insects, nature

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Though summer is well underway here in Britain, I’m not seeing a huge number of butterflies. Here are some I have seen fluttering by in recent weeks.

160624 Common Blue

There are several small blue butterflies in Britain and they can be difficult to tell apart but the Common blue (Polyommatus icarus) is, as its name implies, the most common. As is often the way with wildlife, the males are bright blue, whereas the females can be quite a drab brown.

160624 Holly blue

The Holly blue (Celastrina argiolus) looks quite similar to the Common Blue, especially in flight. The trick to identifying it is in the small black dots on the underwings. It is also the blue butterfly that emerges first from its winter hibernation so look for it near holly plants in early spring, then fluttering about ivy in the summertime.

160624 Orange tip

If this is an Orange-tip butterfly (Anthocharis cardamines), where’s the orange colour? Turns out this is a female and only the males have bright orange wing tips. Still, she’s a very pretty little thing, even if she did seem a bit shy and hid her head behind a leaf.

160624 Large Skipper

Though it’s called the Large skipper (Ochlodes sylvanus), this butterfly is relatively small, its wingspan just a couple of millimetres more than the Small skipper, so you need to look for the mottled brown markings on its upper wings to tell the two apart.