In the past few weeks several residents of Maranoa have asked us about busy swarms of wasps patrolling their lawn. The most abundant of these is variously called the Orchid Dupe Wasp or the Dusky-winged Ichneumonid Lissopimpla excelsa. These are small, red wasps with iridescent, charcoal-blue wings. If one lands for a moment, you may see its jet-black upper abdomen with a series of white spots down each side.
|You might also see a long black needle protruding from the abdomen, but think again before you reach for insecticide! This is a female wasp hunting moth caterpillars. She does this not to feed herself but her progeny. The wasp has long, active antennae with which she will sniff out her prey in the grass. That alarming “stinger” is actually an ovipositor, a sort of egg-laying spike. When she finds her victim, she will hypodermically inject an egg into the body of this unfortunate grass-eating grub. Her egg will later
hatch and the wasp larva will slowly eat the caterpillar from the inside out. It’s a gruesome tale but good news for gardeners. Among the common prey of the Orchid Dupe Wasp are the Cotton Bollworm Helicoverpa armigera and Army worms Spodoptera which are pests of lawns, gardens and crops.
|One caller reported a painful sting but there are several other small red parasitic wasps cruising our lawns in search of grubs. Some species with less obvious armaments carry a nasty surprise. And what about that odd name, “Orchid Dupe Wasp”. While the female wasps search for somewhere to lay eggs, male wasps look after their legacy by searching out females. Males use those long, sensitive antennae to detect pheromones released by females and they complacently follow this scent to its source. It is a system ripe for intrigue, and in areas to the east of Maranoa, that is just what happens.
|Tongue-Orchids Cryptostylis release matching scents to those wasp pheromones, and from the perspective of a keen male wasp, the orchid flower parts are indistinguishable from his desired mate. The male wasp comes away confused and carrying pollen, only to be fooled again by the next orchid. While a moth caterpillar plays unwilling host to the wasp offspring, the wasp is duped into pollinating a plant.