While all may appear tranquil at the London Wetland Centre, beneath the grass an extraordinary battle is raging between two fascinating creatures.

Long-winged coneheads (conocephalus discolor), a type of cricket, thrive at this time of year and can be found living in the nature reserve's sedge beds.

The bush-cricket's high-pitched and shrill stridulation call, made by rubbing its legs together, is barely audible to the human ear, unless you happen to have a bat detector handy.

While their presence is welcomed by staff and visitors alike, fearsome-looking wasp spiders (argiope bruennichi) are even more pleased to see them.

The spiders feed on the crickets and as a result have stalked them across the country over the last 20 years, moving north from the coastal southern counties and up to the capital.

The conehead reached London in 1995, and enjoyed a relatively stress free life for the next seven years until the predatory wasp spider arrived in 2002.

Since then the annual battle for survival between the two has raged.

Jamie Wyver, London Wetland Centre spokeswoman, said: "Wasp spiders can be seen around London Wetland Centre, located in the wetland margins of the entrance lake, south route and Sheltered Lagoon.

"Keep an eye out for more of them as the month of August wears on - several individuals are now impressively big, at about 4 cm with their legs stretched out on their web."

Both species are categorised as a Joint Nature Conservation Committee (JNCC) Nationally Scarce species.