Tag Archives: Gypsy Moth

Natural History, Nature Reserves

More a Bug than a Butterfly Transect

I had a go at the ‘regular’ butterfly transect down at the reserve. It was warm and humid but overcast and it didn’t look promising. A large willow covered in Gypsy Moth caterpillars had been loosened by all the rain, and had fallen across the path. I lopped off the crown branches and carted them down to a dead hedge to fill in a gap someone had been climbing through.

The sun peeped out and the cloud cover reduced to maybe 60%, making it warm and pleasant. A single Small White appeared over the ramp and made it onto the transect. I wandered around the reserve, but there was nothing until I found a solitary Speckled Wood in the large meadow.

However, there was plenty to notice all around. The building site looks a lot better now the ‘Costa Concordia’ white horizontal balcony cladding on ‘Chiswick Point’ (well, it’s in Acton Green and on Bollo Lane, but I guess Bollo Block didn’t quite have the same cachet) has been completed: it will be nice when the noise of cranes and drilling stops.

Handsome iridescent green male Oedemera nobilis on Catsear
Handsome iridescent green male Oedemera nobilis on Catsear

Many ichneumon flies were out on the Hogweed, some mating; almost every Catsear flowerhead had one or two handsomely iridescent green Oedemera nobilis, the “thick-kneed flower beetle” – only the males have the swollen hind femurs, but both sexes have a gap between the slender wing-cases. The males were of noticeably varying sizes, presumably the large ones having the best chances of mating.

Tent of Comma? caterpillars on Stinging Nettle
Tent of Peacock butterfly caterpillars on Stinging Nettle

A fine bustling mass of hairy black early-instar caterpillars of the Peacock butterfly, wriggled on their silk tent atop a Stinging Nettle.

Laburnum leaf beetle larva doing an impressive amount of leaf damage
Laburnum leaf beetle larva doing an impressive amount of leaf damage

The Laburnum by the main path is being eaten full of holes, probably a good thing for a non-native shrub in the reserve, by spotted and striped larvae of the Laburnum Leaf Beetle. Never seen it before.

Mating Rose Sawflies
Mating Rose Sawflies

The wild rose in the car park hedge was host to a mating pair of Rose Sawfly, a serious pest for gardeners but an attractive insect with a bright yellow abdomen.

Large Red Damselflies in cop over a lot of healthy Starwort in the pond
Large Red Damselflies in cop over a lot of healthy Starwort in the pond

As if all these treats weren’t enough, there were Large Red Damselflies mating and egg-laying on the pond, Common Blue Damselflies, lots of Hoverflies, Click Beetles (seemingly Athous haemorrhoidalis), large brown frog tadpoles and small black toadpoles, singing Blackcaps, a Song Thrush, a Jay, and plenty more. Maybe it’s not just Bugs Day on Saturday, but Bugs Week.

 

 

Conservation, Environment, Natural History, Nature Reserves

Gypsy Moth plague

The Gypsy Moth, Lymantria dispar, is  a notifiable pest listed by DEFRA, or at least it was when that document was published back in 1997. The insect was announced to be “a serious pest of trees and shrubs” and nurserymen and landholders were required to notify DEFRA or the PHSI HQ immediately.

Gypsy Moth caterpillar on birch trunk
Gypsy Moth caterpillar on birch trunk: blue warts at front, red warts at back. The black-and-white pattern may also be aposematic

It has arrived in the Gunnersbury Triangle with the hairy dark caterpillar larvae with blue and red warts on their backs all over some Birch trees. The infestation is rapidly defoliating them, and causing substantial damage to some Oaks too.

Lymantria means ‘destroyer’, quite a well-named genus. The caterpillars are aposematic, their hairs and bright coloration warning off predators; the hairs are irritant, containing diterpenes, complex organic ring compounds found in wood and plant resins for defence against microbes and fungi, and retained by the caterpillars for defence against predators.

It will be interesting to see how the trees cope. Oaks can generally recover even when thoroughly defoliated; the Birches may suffer more. People can hardly use pesticides in the nature reserve, even given the means to spray whole trees safely, but biological controls are imaginable. The caterpillars are parasitised by Ichneumon flies, which may well be keeping Gypsy Moths under some sort of control in Europe. There were no controls in place to halt the spread of Gypsy Moth in America, however, where the pest was accidentally introduced in 1869 from Europe by the amateur entomologist Étienne Léopold Trouvelot. He was hoping to cross-breed them with silkworms to improve their disease resistance; he is remembered instead for starting a disastrous continent-wide caterpillar plague which still continues. Attempts with other pest species to introduce their predators or parasites have often proved unsuccessful and sometimes disastrous in their turn.