Flowering plants bring more than beauty to a garden. Many beneficial insects, the kind that help reduce pests on our plants, depend on nectar and pollen to provide nutrients necessary for life. We met some of these characters in previous episodes of Bug of the Week such as the parasitic ichneumon wasp (NEED LINK TO APRIL 7, 2008), the lovely green lacewing (LINK TO APRIL 10, 2006), and the flower flies (LINK TO MAY 8, 2006). A constant array of flowering plants in a landscape may help make it more sustainable. A favorite flowering perennial in my landscape is yarrow. This showy member of the aster family has many medicinal uses in addition to being an excellent attractor of pollinators and pest-eating beneficial insects.
However, not every insect that visits our flowers is necessarily good from our point of view. While pondering yarrow, I noticed several spectacular metallic green wasps dashing about on the flower heads. These gorgeous creatures were cuckoo wasps. Cuckoo wasps share their name with parasitic birds called cuckoos. Cuckoo birds are clever rascals that lay eggs in the nests of other species of birds. The embryos develop rapidly and hatch in advance of their unlucky nest-mates. They young cuckoos proceed to shove the other eggs from the nest and the hapless mother bird unwittingly feeds and raises the cuckoo young instead of her own. Many species of cuckoo wasps are cleptoparasites. As the name “clepto” implies, these little wasps are thieves. Many solitary wasps such as mud daubers and potter wasps (NEEDS LINK TO OCT 9, 2006) are highly beneficial. They capture caterpillars and other pests and store them in tubes or pots made of mud or clay. These provisions are food for developing wasp larvae. Several species of cuckoo wasps lay eggs in the nests of solitary wasps.
The cuckoo wasp’s larvae consume the provisions procured by the solitary wasps for their own young. The name cuckoo wasp derives from this form of larceny. Other species of cuckoo wasps directly attack and kill the young of other insects. Some sneak down the galleries of ground nesting bees like plasterer bees (LINK TO MARCH 27, 2006) we met a few weeks ago. Once inside, the female wasp lays an egg on the bee’s baby and the cuckoo wasp larva devours the unfortunate victim. One wonders why hard-working solitary bees and wasps tolerate this nonsense from cuckoo wasps. It turns out that at least one species of cuckoo wasp produces an odor that closely resembles the smell of its host. This chemical cloak probably helps the cuckoo wasp sneak into the nest of its victim undetected to perform its nefarious deeds.
A cuckoo in wolves' clothing? Chemical mimicry in a specialized cuckoo wasp of the European beewolf (Hymenoptera, Chrysididae and Crabronidae) by Dr. Strohm and colleagues and Microsoft® Encarta® Online Encyclopedia 2007 were used as resources for this Bug of the Week. To learn more about cuckoo wasps, please visit the following web sites.