Monday, August 29, 2011

Beneficial Insects: Ichneumon Wasps

This Ichneumon Wasp is about to lay an egg inside this butterfly pupae.

Ichneumon Wasps
Latin Name: Family Ichneumonidea (over 60,000 species worldwide and over 3,000 species in North America)

Another caterpillar about to be injected with an egg.

Why are they beneficial?
Just picture the Aliens movie genre when I describe these wasps.  Ichneumon Wasps typically don't have the ability to sting in self defense.  The females of the species have long ovipositors (egg laying tubes) in place of a stinger.  Most species inject their eggs into a host's body, and some will include a bit of venom with the injection.  The egg hatches and the larva will eat the host from the inside out as it grows, typically saving the vital organs for last to keep the host alive as long as possible.  The host is usually a larva or pupa (e.g. caterpillars, grubs, beetle larvae, scale, plant bugs, leafhoppers, etc)... species which can often cause great damage in our gardens.

Ichneumon Wasp about to inject a case or bag moth caterpillar in Australia.
This caterpillar constructs a home on its back with material from its environment.  Not safe enough!

What is their lifecycle?
Male Ichneumon Wasps will search for a female with which to mate.  He has no stinger.  After mating, the female will search for a place to lay her fertilized eggs.  Some will lay their eggs in the ground, but most look for a host larvae or pupa.  The female will land on the host and pierce the host with its sharp ovipositor.  At least one egg will be deposited into the host, and then the female will fly away.  It seems that most Ichneumon Wasp species target only one or a few host species.  Each one is different.  Some Ichneumon Wasps only target wood-boring larvae (of wasps or beetles).  These females actually have metal (manganese or zinc) in their ovipositor!

The egg will hatch, and the larvae will feed on the host.  The larval stage can range anywhere from ten days to a few weeks.  Most Ichneumon larvae will feed on the non-vital tissues first and then feed on the vital organs last to keep the host alive as long as possible.  Some larvae never kill the host while in the larval stage.  Eventually, the larvae will pupate either inside the host (with the host sometimes still alive) or outside the host (and they may use the host's remains as part of the cocoon).

The adult Ichneumon Wasp will emerge from the cocoon and will typically begin to look for a mate right away.  Some species have only one generation per year, while others may have two or more generations per year.

Another species of Ichneumon Wasp

What do they look like?
They look like wasps!  Really, they look like skinny wasps with unusual color patterns and markings.  They are usually black or dark colored with lighter colored legs.  Size can range from an eighth of an inch (about 3 mm) to over five inches (12 cm) including the ovipositor.  Females will have long thread-like ovipositors that look like long stingers, but they don't sting - so don't be afraid.  Males lack the ovipositor.  They have unusually long antennae; some species use these antennae to tap along wood to detect hollow spots that house burrowing larvae.

So many species!

What do they need?
Adults typically feed on nectar of flowers, shrubs, and trees.  The smaller the flower, the easier it is for these wasps to feed.  It has been said that ichneumon wasps prefer members of the carrot family.

Examples of plants that provide nectar and pollen to beneficial insects: basket of gold, buckwheat, butterfly weed,carpet bugleweed, chamomile, chervil, chives, clover, cornflower, cosmos, coreopsis, cinquefoil, coriander, dandelion, dill, fennel, four-wing saltbush, golden marguerite, marigold, mustard, parsley, queen anne's lace, scented geraniums, spike speedwell, sunflowers, tansy, vetch, wild carrot, and yarrow.

Adult Ichneumon Wasp drinking the nectar of a carrot flower.

These wasps are not available to buy.  If we create a good habitat for them, they will arrive on their own.

A beautiful female ichneumon wasp, Megarhyssa marcrurus, looking for larvae of the horntail wasp - a wood burrowing larvae.

She found her host and begins drilling with her metal-tipped ovipositor.

Check out these other pages on beneficial insects in your garden!
Praying Mantis
Trichogramma Wasps

1 comment:

  1. Which wasps are available to buy to destroy clothing moth larvae inside house