Tag Archives: Anthrenus verbasci

The ghosts of collections past

The images stopped me in my tracks. These are the haunting signs that will make any entomologist hang their head in melancholy regret at things lost and gone forever.

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Echoes of the butterflies what were once stored in this box.

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… and the swallowtails that were once here.

These shadowy outlines were stained into the paper lining a couple of store-boxes I recently picked up at the Booth Museum of Natural History, in Brighton. They are all that is left of the butterfly specimens earnestly collected, carefully mounted and proudly pinned into the cork by some long-gone entomologist.

Imagine what would happen to the dried insect specimens, pinned into the box (the boxes stored flat to allow some stacking), if the butterfly bodies and wings suddenly and magically turned to fine dust. The dust would fall and settle on the white paper beneath, in exactly the same shape as the insect that was once above, and over the months or years the undisturbed dust would impregnate the white fibres of the lining, casting a tinge of discoloration. All that remains are the naked pins and the small rectangles of the data labels. Now the pins and labels have been removed, leaving their own echoes too.

There is no magic involved, though, just the depredations of the larvae of museum beetles — Anthrenus species. ‘Undisturbed’ is the operative word here. Undisturbed, unmonitored, unseen inside the boxes, a population of museum beetles chewed through the butterflies until there was nothing left but the beetles’ powdery dusty droppings.

Every museum in the world will have horror stories of some precious and irreplaceable collection reduced to dust like this. Store-boxes are especially prone, because they are apt to be left shut up for years or decades at a time. Glass-topped cabinet drawers, at least, can be easily pulled out and examined for the tell-tale dusty signs of an infestation — hopefully caught early on.

Like many museums, the Booth is glad to get rid of all the store boxes it can, transferring the many specimens into standard glazed drawers. And as I’m discussing this with the curators they shake their heads and bemoan the state of so many collections that come their way. This is all very significant for me, because I have just helped them transfer the nine cabinets of my father’s insect collections into the museum, along with a cabinet of snail shells and his herbarium, all of which he bequeathed to the Booth in his will. During his lifetime he was lucky that he never had any Anthrenus infestations.

The museum can heave a sigh of relief that the Alfred W. Jones bequest is pest-free, and there are no signs of any ghostly shadows on the paper linings of the drawers.

Entomologists love all insects, except this one

No matter how small and mean is an insect, there’s an entomologist, somewhere, who thinks it wonderful. Lots of people love butterflies, and moths, and bees, and dragonflies. Dung beetles are among my own favourites. Elsewhere there are fans of stick insects, earwigs, fleas and hissing cockroaches. Even ants, apparently, have their followers.

But, to a man (or woman), there is one insect universally loathed by entomologists of all walks of life. This one.

Cute, but despised, Anthrenus verbasci is the bane of entomology.

The museum beetle, Anthrenus verbasci, is a small (2.0-2.5 mm) globular little beast, very pretty under the microscope because of its mottled variegated scales. But it is the scourge of entomologists the world over. As its name suggests, it haunts museums — in particular the cases of stuffed birds and animals, stores of dried animal skins and drawers of pinned insects.

It is one of several similar species, including the more appropriately named Anthrenus museorum, that can wreak havoc among the museums’ treasured collections, unless each and every item is examined on a rolling check every year or so. Large items, like stuffed birds and animals are often on display and chewings are immediately noticed. But trays and trays of pinned and carded insect specimens locked away in dusty mahogany cabinets in the store rooms can go for decades unexamined; it is not until some visiting expert tries to check out the particular family or genus they’ve been working on, that the Anthrenus infestation is revealed. All that now remains are rows and rows of neatly arrayed pins and piles of dust. No, entomologists do not like Anthrenus.

It is the tiny bristly larvae that do the damage, chewing their way through the insect specmens, often from the inside out. With generation times of only a few days or weeks, it is not long before there is an army of Anthrenus larvae. Oh, entomologists grit their teeth and curse softly under their breath at the thought.

It might seem odd, at first, that Anthrenus should have found this strange little ecological niche in which to have evolved their annoying and destructive lives. And they rather beg the question, where did museum beetles live before there were museums?

Museum beetles do not just live in museums, they also live in homes, where they go by another name — carpet beetles. Here, the same fuzzy larvae, sometimes endearingly called woolly bears, chew away at the Axminster or the Wilton. Not that this gets us much further; OK so where did they live before humans had carpets? Where did they live in the many rug-free millennia before the intricacies of the Persian or the Turkish knot, before the loom, before even the first sabre-toothed tiger skin was cast down onto the cold rough cave floor by Mr and Mrs Neanderthal?

It seems they probably lived in bird and small mammal nests. Despite the fact that museum (or carpet) beetles now frequent our very modern homes and learned institutions, their metabolism is still governed by their digestion of the moulted feathers and fur they first tasted way back in evolutionary history. In the home they find ready nutrition in the wool of our carpets. They will also eat silk (another animal fibre), feathers (whether boas or stuffed birds), furs (stoles, coats and more stuffed displays). And they will attack the chitin shells of museum insect specimens.

The occasional Anthrenus is also sometimes fished out of empty bee and wasp nests. These are often made in the same places as bird and animal nests, either in hollow trees, loft spaces or hedge bottoms. Here they appear to be devouring the remains of dead insects littering the lower regions of the combs. There is very little evolutionary leap from dead bees and the remains of the wasps’ prey, to the insect specimens hoarded away in the local museum.

I don’t like Anthrenus. They have devoured plenty of specimens in my relatively small insect collection including, recently, a large number of parasitic flies (family Tachinidae) stored in a rather old and obviously not Anthrenus-proof store box.

But I do have a soft spot for one of its close relatives — Ctesias serra. The adult beetles are slightly larger, flatter and shinier then Anthrenus, and the bristly larvae are lovely.

The animated boot brush that is the larva of Ctesias serra.

Ctesias follows a quiet and secretive life on old trees where it ekes out a living eating dead insects. These it pinches from the snarled and matted webs of the the several types of spiders that live underneath the loose and peeling bark, or inside hollow trunks. It tiptoes about in the dark nibbling at the dry husks, but is itself immune to spider attack. If a spider comes near, Ctesias starts wiggling its tail, at high speed. This sets up jamming signals across the silk threads of the webs. The spiders are unable to work out where the vibrations are coming from, so cannot calculate a pounce. A spider would only get a mouthful of broken bristles if it tried.

Ctesias is a relatively uncommon species, but occurs on a wide variety of trees, including some of the large street trees here in East Dulwich. Unlike Anthrenus, it does not find abundant food in bird or small mammal nests, nor has it invaded bee or wasp colonies. It has certainly not come indoors to munch the carpet or the soft furnishings. And it has never been found in insect collections. I like Ctesias. I like it a lot.