The unstoppable advance of harlequin ladybirds

 It's now a 14 years since I first saw a harlequin ladybird in Country Durham, and a decade since I first found one in Teesdale. Yesterday, in precisely the same location, there were hundreds, feeding on ivy nectar. This abundant supply of energy in autumn, coupled with their capacity to remain active in cold weather, must surely be important factors in the phenomenal success of this invasive species. 

Harlequin larvae seem to have an affinity with sycamore, perhaps because of the vast supply of sycamore aphids that they find on the leaves. At this location sycamore and ivy grow together, which might account for the population explosion, with dense ivy also providing a sheltered winter hibernation site.

There now seem to be two dominant morphs in this local population, one black with four large, ragged red spots and the other red with multiple black spots, which is more common. 

 This 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 two decades 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.

Ladybird defenders of my blackcurrant crop

 Every year in late spring the blackcurrant bushes in my garden are plagued by aphids that multiply unnoticed under the leaves, until they began to curl. That's usually the time that ladybirds, those useful aphid predators, begin to congregate on the bushes. It's probably the ladybird larvae that are the most effective predators, rather than the adults, so it will be a while before they appear, but these three ladybird species were feeding on the bushes yesterday. They are all very small, about half the size of the most common, most familiar 6-spot species.

2-spot ladybird

10-spot ladybird

14-spot ladybird

Ladybirds

It's been a good year for ladybirds in our garden - here's a selection of the species that have visited so far:

2-spot ladybird

7-spot ladybird

10-spot ladybirds

Melanic 10-spot ladybird - black and red colours reversed

Cream-spot ladybird

Orange ladybird

14-spot ladybird


Most of these appeared on blackcurrant and gooseberry bushes - probably because both have been infested with aphids and mildew that are eaten by various ladybird species.

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.

The ladybird and the ant ....

We found this tiny 22-spot ladybird on a dead hogweed stem in Teesdale a couple of days ago. Teesdale is close to the northern limit of its recorded distribution in England.

According to the UK Ladybird Survey web site this species has a particular liking for hogweed and feeds on mildews. A research paper published in 2011, which you can read here, revealed that these mildew-eating ladybirds are attracted to volatile compounds that are produced by mildew.

What's less certain is why this ant seemed to be engrossed in the hogweed stem. Maybe it too was feeding on the mildew too, or perhaps it had chewed that long trench in the stem tissue ...........

It looks like it's chewing all the soft, rotting tissue from the outer stem of the hogweed.

Whatever the reason, it was very reluctant to move and when I finally disturbed it the ant just crawled into the hogweed umbel and them resumed chewing the plant surface.

14-spot ladybird

Several bloggers, including Caroline Gill at Wild and Wonderful , have remarked on the shortage of ladybirds earlier in the year. We had a few 7-spots in our garden in late spring but, as yet, no second generation individuals of that species.

Yesterday this 14-spot ladybird put in an appearance. This is one of the smaller species, less than 4mm. long, with very variable colour patters. The typical form has 14 distinct spots but this form, where some of the spots merge to form an anchor shape on the elytra, is quite common too.

This species feeds on aphids and this individual had a tiny victim in its jaws.