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The large range of native plants in our cold climate garden attracts many insects. We find that, because of the size of the garden, insects cause very little damage to our plants. In fact, we feel that the majority of native insects are either useful or benign.
Blue Flower Wasps are frequent visitors and appear in our cold climate garden from mid summer to early autumn. They are eye-catching, steely-blue wasps, about three centimetres long, who spend their time zooming around, often close to the ground and feeding on flowering native plants. We have observed the wasps feeding on the nectar of Baeckeas, Leptospermums (Tea trees) and Bursaria spinosa (Blackthorn).
After mating female wasps burrow into the ground, paralyses Scarab (Christmas Beetle) larvae then lay an egg on the grub. When the egg hatches breakfast lunch and dinner are laid on for the wasp larva.
Blue Flower Wasps are parasitoids. These are insects that slowly kill the host usually near the end of larval development. This contrasts to parasites that usually do not kill their hosts.
Many years ago we spoke to an entomologist, at the University of New England, whilst watching Blue Flower Wasps feeding on Kunzea flowers. He said that three species occurred in the area and identified the three species on the Kunzea. One species was totally steely-blue, another had a yellow head (see image) whilst the third had yellow markings on the body.
Blue Flower Wasps are useful insects. They assist in the pollination of native plants and help control the number of Christmas Beetles that in some years will defoliate eucalypts.
Flower Wasps are also found in the USA and North Africa.
We have often wondered how the female wasps detect the underground beetle larvae. Sometimes the larvae are 15 centimetres deep. They are very successful in their larvae detection because during the warmer months our garden is host to large numbers of Blue Flower Wasps.