Wednesday, November 6, 2013

No ladybirds for months, then five species all at once.....

Thursday's Guardian Country Diary describes encounters with ladybirds in Weardale and Teesdale.

Back in the spring it seemed as though 2013 might be a good year for ladybirds locally - plenty of 7-spots seemed to have come out of hibernation so I anticipated a thriving population by the time their offspring hatched in summer - but it never seemed to materialise. I found a few isolated individuals of other species - notably 22-spot , 14-spot and an orange ladybird  but then last week .........


........ this huddle, near a pine plantation at Wolsingham in Weardale. It was the largest number of 7-spots I'd seen in one place all year: six that had chosen a split in a fence post as their hibernation site. 7-spot ladybirds aren't usually associated with conifer plantations but his particular row of fence posts, on the sheltered, south facing side of the plantation, as always been a good place to find other species



So it was no surprise to find this eyed ladybird - a conifer specialist - sunning itself on the same line of fence posts.




A small, unidentified fly with unusual up-turned antennae had even chosen to hitch a ride on it. The eyed ladybird is our largest species but ...


...... this one, a larch ladybird that shared the same fence post, is one of our smaller species ...

..... here going head-to-head with a staphylinid beetle (which it simply head-butted out of the way!)



Then, a day later at Egglestone in Teesdale I found ivy in full flower that had attracted several orange ladybirds, that were feeding on nectar.























You can see here the translucent pronotum of this species, that used to be considered scarce but seems to have increased in abundance in recent decades, supposedly because it has taken to feeding on fungi that grow on the honeydew secreted by sycamore aphids. On one occasion a few years ago I found a cluster of ten of this species hibernating on the bark of a sycamore in winter - it's certainly a species that can be added to the very small number of insects that are associated with sycamore, which has been present on these islands for around 500 years but has a very small insect fauna.



Close to the orange ladybirds on the ivy I then found a single 7-spot sunning itself on a fence post and ......


.......... scores of this very unwelcome addition to our ladybird fauna - the harlequin. The first time I saw these locally was in Durham city back in 2009, on ivy flowers at almost exactly this time of year. Harlequins are noted for their bewildering range of colour patterns but the indentations at the tail end of the elytra are also a distinctive feature, although they too vary in extent between individuals.


This group of about a dozen individuals had just hatched from their pupae and were still developing their full colours. Harlequins have a breeding season that extends well into autumn.


Some, that also seemed to be the most rotund individuals, were almost entirely black ...


..... but his was a more typical colour pattern in this population.





Finding another population of harlequins was an unwelcome discovery because this disease-resistant species is known to be a predator of our native ladybirds and can also transmit a parasite that kills other species. It also feeds extensively on eggs of butterflies and moths. Over the last decade it has spread rapidly from south east England to the Scottish border. It originated in central Asia but was introduced elsewhere in misconceived biological control programmes aimed at 'environmentally friendly' aphid control in greenhouse crops. Wherever it has been introduced it has escaped and has had a detrimental effect on native insect populations.


The predominantly black individuals seem to have blue eyes.


This was the last unhatched pupa, attached to the fence posts. At the point of attachment you can just see the remains of the larval skin, which is spiny in this species. 

Harlequin larvae also seem to have an affinity with sycamore, perhaps because of the vast supply of sycamore aphids that they find on the leaves - so it may well be that orange ladybirds will also form part of their diet too.

If you find harlequin ladybirds you can report their presence by contributing the record to the Harlequin Ladybird web site.







6 comments:

  1. What an abundance!

    What is one supposed to do, other than reporting the Harlequins? Does the Society give advice on controlling them?

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    1. Judging from experience in the US and elsewhere there's little hope of controlling their spread, toffeeapple. Anything that kills them in the wild is also likely to kill native ladybird species.

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  2. Harlequins are something I haven't come across.
    Something is causing changes in the behaviour of frogs here. They had almost disappeared during the monsoon season, but now, thankfully, I am coming across them often.

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    1. Worrying news about the frogs lotusleaf - they've been badly affected in many parts of the world by lethal chytrid fungi.

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  3. A truly stunning post! I guess habitats and vegetation vary a bit between the north and the south, but I haven't seen half the colour variations you have posted down here. For me it's been a year of big clusters and then weeks without a Ladybird at all ...

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    1. Thanks Caroline. The ladybird that I almost never see now is the two-spot, which used to be common.

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