Paper wasps menace monarch butterflies
If you haven’t seen many monarch butterflies this year, it could be because there’s a national shortage this summer.
Commercial butterfly growers Ian and Jill Knight released about 100 monarchs into the wild on Saturday. The Knights’ farm, at Hope near Nelson, has four tunnel-houses, each filled with hundreds of monarchs in various stages of development; when the butterflies are mature, they are sold or released into the wild.
Ian Knight said that this summer there was a ‘‘huge shortage’’ of monarchs, which he believed was primarily due to the asian paper wasp.
‘‘They’re the biggest threat [to monarchs] at every stage of life, from egg and caterpillar to chrysalis and butterfly.
‘‘Last year we had about 300 butterflies in one tunnel-house ready to release, and the next day I went in, the floor was just littered with dead butterflies and there was one wasp that was in there, in a stinging frenzy.’’
Knight said he killed the wasp but the damage was mostly already done: of the original 300 butterflies, 150 died.
The Knights run a business, Occasional Monarch, which sells monarchs to be released at special events like weddings, funerals, and unveilings.
They send carefully boxed-up butterflies through the post in chilled containers, ready to be released after warming up again.
The butterflies are completely unharmed by the process, as being kept in cold, dark conditions simply sends them to sleep. The Knights have even kept butterflies in the fridge over winter, feeding them every 10 days, to give themselves a head-start for breeding when the weather warmed up again.
They said wild butterflies often came to the farm to lay eggs through the protective netting on to the swan plants inside but this year the number of wild monarchs returning was lower than previous years.
Jill Knight said they regularly checked the tunnel-houses for wasp-invaders and the kill any paper wasp hives they find.
Unlike common or german wasps, paper wasps only take live prey and so do not respond to poison bait like Vespex. Instead, paper wasp nests must be killed individually with over-the-counter pesticides.
Paper wasps can be identified by the long, dangling back legs that hang below them when they fly. German and common wasps tuck their legs up to fly.
Three species of paper wasp are established in New Zealand: the asian, australian and european. Jill said she and Ian were in it for the long haul to keep butterflies safe in New Zealand.