Friends and foes

A sunny Saturday morning was earmarked for taking part in the Big Butterfly Count, but soon we had moved from spotting butterflies to identifying their progeny. Opening the garden shed had revealed a mass of dull green caterpillars with brown heads, encased in silky webbing on the inside of the door.

The door, firmly glued, took some prising open.  The wood around the caterpillars was scarred, and the presence of saw dust suggested they were eating the shed.

Immediately we were concerned. How much damage would these caterpillars do? Imagine if they got into the house and were eating their way through our roof and floorboards. We needed to find out what they were.

Enter the power of Twitter and, with it, the generosity with which so many experts share their knowledge and expertise.  Tweeting photos of the caterpillars began a chain of discussion and a possible identification; these could be the caterpillars of the wax moth Galleria Mellonella.

I had read about wax moths in various books on beekeeping: they are associated with honey bees and considered a pest by beekeepers.  But that was all I knew.  Intrigued, and wanting to know more, I looked up Galleria Mellonella and was surprised to find it mentioned that they can also pose a threat to bumblebees.

The penny dropped.  For weeks we have been watching bumblebees going in and out of a gap underneath our garden shed – a sure sign of a bumblebee nest.  Could the sudden appearance of these caterpillars be coincidence?

I realised now how little I knew about bumblebee nests, and the life of the bees when not out and about foraging in the garden.  I still didn’t understand the connection between wax moths and bumblebees – bumblebees don’t produce wax do they?  Well, yes, they do.  Wax pots are used to store their honey, pollen and brood.  I wanted to find out more.

An informative article by Kate Bradbury revealed that once the wax moth caterpillars have had their fill they move out of the nest. I feared the worst. Had these caterpillars already done their damage, moved out, and begun to get ready to pupate?

More information came in by Twitter, this time from leading bumblebee expert Dave Goulson, author of A Sting in the Tale, who told us that the caterpillars of another wax moth Aphomia sociella eat bumblebee brood and wax.  He finished by tweeting ” = destroyed bbee nest”.

It’s difficult to tell the effect on our bumblebee nest because the recent wet weather is no doubt inhibiting activity, but I certainly haven’t noticed the usual comings and goings of the bumblebees in the last few days.

I am grateful to the following people on Twitter for helping to solve the mystery of the shed-eating caterpillars, and heartily recommend following them:

@Greengrumbler @RichardComont @bugboybaker @EntoProf @BBCNature @Coleopterist @Kate_Bradbury @DaveGoulson

I tweet about bees and related topics from @meadow_land

2 thoughts on “Friends and foes

  1. Fascinating photos of a nasty pest. As you say, wax moths are a real concern for beekeepers. I dread the sight of them. And they are a real threat to bumblebee nests; my neighbour had a camera on a bird nest box and saw it taken over by bumblebees – and then wax moths. She wasn’t sure what was happening at first and then realised that the bumblebees were trying to carry on even though the wax moth was destroying the nest.

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