Leaf beetle

Cow Parsley Leaf Beetle (Chrysolina oricalcia)

Earlier this week, a metallic bluish-black beetle clinging to the stem of one of the Cow Parsley (Anthriscus sylvestris) plants in the garden caught my eye. Some research online and in our various insect books showed it to be a Cow Parsley Leaf Beetle (Chrysolina oricalcia). Though shaped a bit like a flea beetle (without that group's bulging "femurs"), it's far too big, measuring nearly a centimeter in length (about a half-inch). Its rounded elytra – the hard shells that cover and protect its wings – are sprinkled with rows of tiny pits. Though fairly widespread across south-eastern England, it's listed as "Nationally Scarce" and may be declining in some areas. Their scarcity certainly isn't due to a restricted food source; the insects feed on Cow Parsley and related plants, which are common and widespread across the whole of the British Isles. Adults feed on leaves and possibly pollen, while larvae munch leaves, generally feeding at dusk and dawn or during the night. The species overwinters as adults, though no-one yet knows where. Since finding the first beetle, we've discovered a number of larvae on various plants around the garden, so it looks like we'll be hosting this scarce species for a while to come!

Larva

Cleaver gall

Cecidophyes rouhollahi on Common Cleavers (Galium aparine)

While wandering around the garden the other day, I found a patch of Common Cleavers (Galium aparine) that looked rather strange. Some of the plants' upper leaves were pale and twisted, forming what looked like curly little tubes. They've been attacked by a gall mite, Cecidophyes rouhollahi. The presence of these mites causes the edges of the leaves to thicken and roll up, encasing the mites safely in the middle. Apparently, the pale leaves often go rust-coloured with time. Surprisingly, this mite was only described for science in 1999; prior to that, another closely related species was thought to occur in the UK. However, more careful studies since than have found no evidence of the other species, while C. rouhollahi has proved to be common and widespread across the islands. In places where Common Cleavers and the closely related False Cleavers are invasive non-natives (Canada, New Zealand, etc.), the mites can be used as a form of biological control as they stunt the plant's growth and keep its seeds from forming.