My apologies: this is one of the most interesting bad photographs I’ve ever taken–a female ichneumonid wasp using her 4″ ovipositor to lay an egg deep inside a piece of our firewood. Unfortunately, it found her in action at 8:30 last night on the way in from shutting the chickens in the coup. The little Powershot does not do well in macro with a flash.
** 2010-05-28 1231PM update: got a daytime shot and replaced the crappy night shot that was up first thing this morning. Click for enlargement.
This is an amazing and baffling phenomenon. You can find ample explanation of the what, not so much on the how.
Both sexes will wander over the surface of logs, and tree trunks, tapping with their antennae. Each sex does so for a different reason; females are searching for the scent of wood boring larvae of the horntail wasps (hymenopteran family Siricidae) upon which to lay eggs, males are searching for emerging females with which to mate.
Upon sensing the vibrations emitted by a wood-boring host, the female wasp will drill her ovipositor into the substrate until it reaches the cavity wherein lies the host. She then injects an egg through the hollow tube into the body cavity. There the egg will hatch and the resulting larva will devour its host before emergence. How a female is able to drill with her ovipositor into solid wood is still somewhat of a mystery to science, though it has been found that there is metal (ionized manganese or zinc) in the extreme tip of some species’ ovipositors. The adult insect, following pupation is faced with the problem of extricating itself from tunnels of its host. Fortunately, the high metal concentrations are not limited to the female’s ovipositor as the mandibles of the adult are also hardened with metals and it uses these to chew itself out of the wood.
Find excellent images (taken in daylight!) here too…including a video of the process. The author-photographer reminds us that…
…Darwin…thought the monstrosity too evil for God to have thought of it, much less condone it.
He wrote, in 1860, “I own that I cannot see as plainly as others do, and as I should wish to do, evidence of design and beneficence on all sides of us. There seems to me too much misery in the world. I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of Caterpillars, or that a cat should play with mice.”
Darwin didn’t appreciate that these “monstrosities” serve as beneficials preying upon harmful agricultural and forestry pests, sustaining an overall balance in the delicate economy of Nature.