Beetle with eyes like opals - an update

I recently posted some pictures of this ground beetle with abnormal milky-white eyes and asked if anyone knew the cause (click here for post with more pictures)

I also posted a picture with the same request on Twitter and after it had bounced around for a bit got a reply from entomologist Dr. Ross Piper @DrRossPiper who identified the likely cause - a parasitic gordian worm aka nematomorph aka horsehair worm, that grows in its host and can have this effect on its cuticle. Infected hosts tend to wander around in broad daylight and seek water, where the parsitic worm emerges from its host to breed.

He sent me the link to this amazing footage of a tropical example (WARNING:GRUESOME)

Gordian worm emerging from a grasshopper


Really wish I'd captured the beetle and brought it home now.

Bee-fly - every mining bee's worst nightmare?

I photographed this bee-fly Bombylius major on a sunny bank neat Thorsgill wood in Teesdale last week.

These furry little flies that mimic bees are parasites of mining bees and several of them seemed to have just emerged from their underground nursery in bees' nests.

Their first actions on emergence are to feed on nectar, darting from blossom to blossom with incredible speed, rarely stopping to settle and usually just hovering in front of a flower, sucking up nectar with that long and deadly-looking proboscis.Violets and primroses, both flowering at this site, are popular nectar sources. 

Few flies look so menacing but they are totally harmless - unless you happen to be a mining bee.

When mining bees dig their new tunnels and provision them with pollen for their developing larvae a bee-fly will hover close to the ground near the entrance,flicking eggs into the tunnel entrance with its tail. When the eggs hatch the larvae will eat the mining bee host's own larva.

You can find more information, a bee-fly ID guide and a video of the insect laying eggs at http://www.brc.ac.uk/soldierflies-and-allies/bee-flies

A bumblebee's worst nightmare?

The arrival of these mating thick-headed flies, which I think are probably Conops quadrifasciatus, is very bad news for bumblebees nesting in our garden. They're parasites, whose larval stages feed on the body fluids (haemolymph) and ultimately on the internal organs of their bumblebee hosts.

Female thick-headed flies spend much of their time on flowers, waiting for bumblebees to approach, then they grab them - often while the bee is still in flight. They have specially-adapted reproductive structures on their tails which prise apart the hard segmental plates of the bee's exoskeleton, so that they can insert an egg through the softer tissue in between. As many as a third of worker bumblebees in a colony can be parasitised and there is some evidence that even in the early stages of infection the behaviour of the bees is affected, so that they spend more time collecting nectar for their own consumption and return to the nest less frequently.

There are plenty of published accounts of the way in which Conops lays its eggs in its host but in a quick search of Google images I couldn't find any of the parasite attached to, or laying its eggs in the host either when they were at rest or in flight - it seems to happen quickly and would be something that anyone would be lucky to see, let alone photograph.

It's a tough life being a worker bumblebee: if you're lucky you work from dawn until dusk all your short life; if you are unlucky you meet Conops.............

Life and death in the cabbage patch .....

This year we've had record numbers of small white Pieris rapae butterflies in the garden. At one point I counted twelve feeding on a single lavender bush - which is bad news for our brassica crops but does create some wonderful opportunities for watching insect behaviour.

Small whites lay their eggs singly on the underside of cabbage leaves ....

.... and the first thing that newly-hatched caterpillars do is to eat their own egg shell. At this stage the caterpillars are yellowish and translucent but as soon as they begin feeding .....

..... you can see the cabbage leaf that they've eaten travelling through their gut.

They are really feeding machines and begin on the underside of the leaf because the waxy leaf cuticle is much thinner there than on the upper surface, where the cuticle is very thick and probably too tough for an infant caterpillar's jaws. You can see here that it has only chewed through the leaf as far as the upper cutcle and hasn't bothered to eat all the way through, except for a small hole. but there's another good reason for stayinging under the leaf .......

.... the constant threat from parasitic hymenopterans. With their jerky movements and twitchy antennae, they are always on the lookout for a caterpillar to lay their eggs in ....

..... and this one found a victim, depositing its eggs inside the tail end of a caterpillar which was on the upper surface of the leaf and is now doomed to be slowly eaten alive.

This one took violent evasive action, dropping from the leaf and swinging on a silken thread was soon as it felt the presence of the parasitic wasp.......

.......... while this much larger one is feeding really dangerously, up amongst the flower buds on the bolting brassica - but maybe it's already parasitised anyway. [Thanks to Africa Gomez at BugBlog for identifying this caterpillar and the one above as the cabbage moth)

Much is made in the press about the effects of recent extreme climatic events on butterfly numbers but parasitism of butterfly caterpillars might be at least as important in determining fluctuations in butterfly numbers from year to year.

The inflorescences produced by the bolting brassicas are a good food source for hoverflies and also home to other visitors, like this harvestman spider - a scanenging omnivore which wouldn't be averse to eating the occasional butterfly egg or newly-hatched caterpillar.

Killer unmasked ....

A couple of weeks ago I posted some pictures of a drinker moth caterpillar, together with the larvae and pupae of the parasitic insect that killed it. The killer has emerged from the pupae and it looks like a tachinid fly of some kind.

You can see the prominent calypters at the base of the wings, which are a tachinid characteristic.

This individual has just emerged from its pupa and its wings have yet to expand.

A nasty way to go ....

A few days ago my youngest son and his partner called to say he'd found a drinker moth caterpillar but by the time I went to collect it the caterpillar had stopped feeding and become very lethargic - usually a sign that there were internal parasites gnawing at its entrails.

Sure enough, a day later this little charmer emerged. The maggot burst out from between the segments on the underside of the caterpillar.

The black structure that you can see at the head end seemed to be some kind of horny beak, that it used to cut an exit hole through the caterpillar's skin. Within two days eleven more of these maggots emerged and one by one ............

........ turned into a red pupa within a few hours of emergence. I suspect it's a tachinid fly (click here for pictures of the fly), although I won't know which one until the pupae hatch.

Mellow yellow

Yellow brain fungus Tremella mesenterica, growing on a dead branch of a large Cotoneaster in Kirkby Stephen in Cumbria. This fungus didn't kill the branch; it's a parasite on another fungus in the genus Peronospora, which had already killed the branch. The fungus is paler when young, but matures to this vibrant shade of chrome yellow.

This aspen Populus tremula, growing in upper Swaledale in North Yorkshire, is the brightest tree in the local landscape at present, beating strong competition from birches and rowans. Aspen leaf stalks are laterally flattened so each leaf flutters from side to side in the slightest breeze and the whole tree seems to shimmer.

Pictures of the winter buds of aspen here and of the fungus that attacks its leaves here.

Hot Bird

Every afternoon this week this blackbird has been sunning itself in the hottest spot in the garden, in our potato patch. It sits in a trance, wings spread out, panting with its beak open, eyes glazed over .... and potentially easy prey for cats. Given the risk, there must be some biological imperative for this behaviour. The favourite theory seems to be that the heat forces parasites in the feathers on its back to move around, making it easier for the bird to reach them with its beak.

The Ultimate Mega-Tick for a Birder?

Last week, when we were walking along the cliff tops south of Seaham, all the blackthorn and hawthorn bushes were alive with the songs of whitethroats. Coincidentally, on the same day I happened to read a recently published scientific paper in the journal Ticks and Tick-borne Diseases , authored by scientists at Health Protection Agency at Porton Down, at the Portland Bird Observatory and at the Food and Environment Research Agency that cast light on a less welcome aspect of the arrival of these annual summer migrants. They found that whitethroats and wheatears were often infested with the tick Hyalomma marginatum that transmits Crimean-Congo haemorrhagic fever, which has occured with increasing frequency in Eurasia and kills up to 30% of its human victims. You can read gruesome details of this disease here. 

I remember, years ago, rescuing a swift that had become trapped in a house loft and watching with fascination as a tick crawled out from behind its eye, bit me on the thumb then crawled back amongst the feathers. In the light of this scientific paper, I'd think twice about handling any bird without gloves.

Tormented

This weary bumblebee landed on our conservatory windowledge this afternoon and began grooming. While I was photographing it a tiny pink acarine mite (which I think is Parasitellus) crawled out of the fur under the bee's wing, climbed down under its abdomen and then climbed up its thorax...

... before crawling down into the fur again between the head and thorax. The bee was clearly irritated by the mite and tried to comb it off, with no success.

Here you can see it burrowing down behind the bee's head. Opinion seems to be divided about how much damage these mites do. It may be that - like the Varroa mite that infests honeybees - some species transmit diseases between bumblebees and some species may weaken their host when they suck its body fluids through weak points in the bee's joints, where they attach themselves. Apparently Parasitellus doesn't feed on bees but merely uses them for transport between bees' nests, where it feeds on the wax of the brood cells. I suspect that pink patch on this bee's knee is another mite, tucked in between the joints in the leg. Some mite species actually enter their hosts body through the spiracles and live attached to the respiratory organs, as internal parasites. Such mites weaken their host, although their effect isn't likely to be as devastating as thick-headed flies, whose larvae live as internal parasites of bumblebees.

Tachina

Hogweed umbels attract all manner of insect visitors, including this very striking fly Tachina fera, which has a gruesome life history. It has two flight periods, from May to early June and from July to September.

This tachinid fly lays large numbers of small eggs on vegetation and when they hatch the grubs, alerted by vibrations from an approaching potential host noctuid moth caterpillar, attach themselves to it  and bore into its body, where they develop as internal parasites. There are numerous tachinid fly species, illustrated at the Tachinid Recording Scheme web site.

Ruby-tail wasp

In my last post I outlined the gruesome breeding habits of the spiny mason wasp, that provisions its nest with paralysed weevil grubs for its larvae to feed on at a later date. In the spirit of Jonathan swift's famous observation, that....

 naturalists observe, a flea

Has smaller fleas that on him prey;

And these have smaller still to bite ’em;

And so proceed ad infinitum.

... here is the mason wasp's nemesis, the magnificently be-jewelled ruby-tail wasp Chrysis viridula. I watched this deadly little parasitoid's behaviour while I was photographing the mason wasp's nest, at the base of the cliffs at Hawthorn Hive on the Durham coast.

There are many species of ruby-tail wasp, also known as cuckoo wasps, each a parasite of a particular species of host wasp, and one thing that they have in common is relentless, restless activity, constantly using their downward-curving antennae to pick up a scent trail in the soil. Ruby-tail wasps have a thickly armoured, iridescent exoskeleton that's impervious to the stings of an angry victim. This species is less than a centimetre long and its colours are more exquisite than anything a jeweller could create.

Once it finds its host's nest hole it uses its antennae to explore the entrance, presumably testing for the specific scent that identifies its prey. Recent research suggests that ruby-tails can produce compounds in their exoskeleton that mimic the scent of their host and so avoid detection and counter-attack.

Next the ruby-tail crawls head-first into the nest hole, to make sure there's no one home, then ....

....... it climbs out and reverses in ....

... until only its metallic green head is visible in the entrance. Inside, it lays eggs that will hatch and produce larvae that will eat its host's young and their weevil grub food store. The hapless host , returning to seal its nest, will never know that the ruby-tail has visited and that its young are doomed.

Thick-headed Flies

Conops quadrifasciata pairs remain together like this for some time after mating has taken place, and take to the air in unison

Females have a more slender abdomen that's sharply curled under at the tip

The exceptional width of the male's head is visible here. Maybe it's because the female's vision is obscured by the male above, so he has to act as look-out for both of them

These flies, mimicking wasps and linked together during mating in characteristic biplane arrangement, as thick-headed flies Conops quadrifasciatus that I found in a field of ragwort in Durham. The bottom photo shows the broad head which gives these insects their common name. They’re parasites of bumblebees, laying eggs on the adult bees which are then literally eaten alive by the parasitic larvae. One study carried out in Switzerland and published in 1990 found that almost 35 per cent of workers of early bumblebee Bombus pratorum and common carder bee B. pascuorum sampled in August contained this parasite’s pupae. At this time of year there are always a lot of sleepy-looking bumblebees apparently resting on flowers and showing little sign of feeding, and many of these are likely to be suffering from parasites, including conopid fly infestations. There’s no doubt that habitat destruction has been a major factor in bumblebee decline, but it’s also true that parasite infestations can have a very significant impact on local populations too.

Assassin

Watching this little hymenopteran (can anyone help with the identification?), only about a centimetre long, working its way through the florets of the grasses around my garden pond, provided a chilling insight into this deadly parasite’s hunting technique. Equipped with a long egg-laying tube (ovipositor), it parasitized insect grubs inside the grass florets without ever seeing its prey. The pictures give a clue to how it manages this. It moved from floret to floret, pressing its antennae against each in turn (bottom picture). How did it find them? Was it scent picked up by its antennae tips, or did they detect vibrations from a wriggling, hidden victim? I have no idea, but what is certain is that as soon as it located a hidden host the parasite slid that stiletto-like ovipositor into a floret (top picture), presumably laying an egg in an unfortunate victim whose destiny was to be eaten alive by the hymenopteran's hatching larva.