Well I didn’t think it would take so long to get around to writing about my pond again but then I have had my new moth light trap to play with…. It turns out there is at least a possible link between the pond and some of the species I’m finding in the trap. One of the two new moths I found this morning was a Gold Spot, Plusia festucae which, despite a specific name which makes me think of fescue grasses (Festuca spp), has larvae which feed on aquatic marginals such as sedges, Iris and Water Plantain.
This bonny moth, with its iridescent forewings, is in the Plusinae sub-family of the Noctuidae, like the Plain Golden Y, Burnished Brass and Dark Spectacle moths I was seeing in July. The characteristic resting shape comes from the way the trailing edges of the forewings are brought together over folded hindwings, forming a sort of tent over the body.
Like most of the Noctuidae, these stout-bodied moths fly from dusk. Adapted for powerful, manoeuvrable flight, they need to refuel as they go on nectar from flowers such as Buddleia, Red Valerian and Honeysuckle, two of which they can find in my garden. Whilst the other three moth species are common in gardens, with larvae which feed on nettles, dead-nettles and other herbaceous plants, the Gold Spot prefers damp habitats beside ditches, canals and rivers or marsh and fenland – or perhaps in this case the edge of a pond.
In northern Britain, Gold Spot moths manage only a single generation between late June and August each year, though I guess that might change with a warming climate. It overwinters as a small larva, produced in September, then pupates in a transparent white cocoon spun vertically between the leave or stems of rushes in May, according to Waring and Townsend’s field guide. Sadly, I can’t find any reliable pictures of the caterpillars online so I know what to look out for.
These Gold Spot moths are not the only sign of a new habitat appearing in my garden, though. This week we’ve had a damselfly sitting on the washing line (too shy to hand around for a photo, sadly) and a frog enjoying a bath in the now-tepid waters of the pond.
The frog, at least, is not at all worried by the algal bloom which seems to be rather swamping my Water Crowfoot at the moment. Martyn has, of course, checked out the algae and assures me it’s filaments of green Oedogonium covered in an epiphytic diatom Fragilaria gracilis, which likes nutrient-poor conditions, so eutrophication is not the problem here. More likely the recent hot weather has just sped up the algal growth so it’s out of synch with the grazers which normally keep it in check. The solution is just to pull a handful out now and again and throw it on the compost heap – nothing more drastic is needed, despite what some garden experts might suggest. I did put half a dozen Ramshorn snails in the pond in July and hope that, as they grow and feed, the algae will stay in balance.
The other part of the new ecosystem developing is on the logs I placed around the pond to cover up the remaining exposed liner and to try and provide more habitat for invertebrates. I was delighted to see fruiting bodies of Jelly ear fungus, Auricularia auricula-judae, appearing on one piece of wood. The plot thickens – or at least the food webs do!