Have been out and about in local (Gloucestershire) apple orchards recently examining their mistletoe for signs of overwintering mistletoe insects. Little is known about the biology of our six mistletoe specialist insects, and how they spend the winter, and how they emerge, is one of many mysteries. I reviewed current knowledge on these insects, and challenged some of the assumptions being made about them, in a recent paper – which, if you’re interested, is downloadable here)
Accepted wisdom says that the Mistletoe Marble Moth spends the winter as a young larva, within a tiny leaf-mine in mistletoe leaves. These mines are, so the accepted story goes, crescent- or comma-shaped. Well, I’ve been round lots of orchards this week, and examined (very) large numbers of mistletoe leaves, and the only tiny leaf-mines I’ve seen have been straight ones. Is that the moth? Or something else entirely? I don’t yet know…
The four mistletoe bugs shouldn’t be active yet – far too early. But how do they overwinter? And what were the instar (larval) bugs I’ve seen this week, already crawling, very rapidly, through the mistletoe?
And then there’s insect number 6 – the mistletoe weevil. Last summer I found that their habit (as larvae) of eating away the mistletoe stem, within the plant tissue, just below the terminal bud, often killed that bud. So, this week I’ve been looking out for dead terminal buds without an exit hole (a hole shows that the adult weevil has emerged). And I found several – which, on dissection (see pic left), provided me with a rather annoyed-looking weevil larva. So that’s how they over-winter – within their cosy little homes inside the stem…
And we mustn’t overlook the pollinating insects. Our mistletoe flowers now – February – and it is insect-pollinated. That might seem odd for February, but it seems to work, so it can’t be that peculiar! Again, conventional wisdoms say that it is pollinated by small flies, and certainly today, in the sunshine, there were several gnat-sized flies frequenting the mistletoe clumps.
But there were also bees – proper honey-bees (see pics below) – probably finding that mistletoe was one of the few plants available to them this early.
I wonder what would mistletoe honey be like?