Underground Inverts

Invertebrates of the Bronygarth Cave

Wren sits at the Cave entrance

The river Ceiriog rushes past, swollen after the latest rainstorm. Partially shrouded by leaves, a small fissure in the limestone rock opens into the cave.

While temperatures decrease in the valley as winter looms, within the cave they remain at a steady 10˚C or so. Wren the dog wandered down the steep bank, taking care not to slip on the fallen leaves and ventured, tentatively, into the stone mouth.

The morning’s moth trap had offered nothing but countless midges. However, metres inside the cave’s entrance a Herald moth hibernated!

Herald moth - Scoliopteryx libatrix

Sparkling with water beadlets, a group of 6 or 7 moths were huddled into crevices, hibernating through the winter months. On the floor of the cave a less pleasing sight was beheld, one unlucky Herald had succumbed to a fungal infection. Dead, it now sported a hugely impressive cauliflower shaped mass on which a small snail happily munched.

A fungi infected Herald

Further into the cave, a Common Striped Woodlouse peacefully rests on the rocky wall.

Common Rough Woodlouse - Oniscus asellus

Nearby, a wonderfully named Slightly Garlic Snail (Oxychilus navarricus) slides about, feeling the darkness with its eyestalks.

Slightly Garlic Snail - Oxychilus navarricus

Sensing movement, a large leggy creature scuttles across the wall. Long striped legs rest on gossamer thin strands of silk, waiting for unsuspecting mosquitoes to make a wrong move. Suddenly the creature darts out, snaffling the prey in an instant. Exposed on her web she proceeds to eat her morsel. She is a Cave Spider, Meta menardi, measuring almost 5cm across she is one of the UK’s largest spiders. Although common she is rarely seen, preferring to spend her life in caves, well away from bothering Humans.

Cave Spider - Meta menardi

Mosquito, potential Cave spider prey.

Back in the cave entrance, and next to a juvenile Cave Spider, three Eristalis pertinax hoverflies are huddled, spending winter in hibernation.

Hibernating Eristalis tenax Hoverflies

Wren, now hungry, meandered her way back home for tea.

Inside the cave, the temporarily clandestine invertebrates snore peacefully, waiting for the warm breath of spring to return.