Thursday, October 11, 2018

Pt. 2 - These Zombies Don’t Eat Brains – But They Might Have Theirs Eaten.

In my last blog, I offered an overview of zombies in the insect world and showed you some of its stars. When writing that blog, I quickly realized that there is a whole Milky Way of zombie-making stars that should be shown. What follows are some of those stellar parasites that I did not get to before.

Dinocampus coccinellae: These parasitic wasps prey on cocinellid beetles, which include the ever-popular ladybug. The wasp attacks the bug and injects an egg into it.Included with the egg is a nice little dose of a virus that paralyzes the ladybug.
Lady blue sitting on a straw-like Dinocampus coccinella cocoon
Ladybug sitting on a Dinocampus coccinella cocoon.
About 3 weeks after the egg has been laid, the wasp larvae pushes out of the bug’s body and weaves a cocoon between its legs. Here’s the twist in this scenario: the ladybug is not completely paralyzed; it is left with the ability to twitch around (which works to keep predators away), but unable to leave the cocoon. In this way, it becomes a zombie babysitter. All’s well that ends well for the ladybug though; once the wasp offspring are ready to venture out on their own the ladybug is released from its bondage. The ladybugs continue on with no apparent damage from their alien abduction.To see how they come out of this check out this video.

Long tangled mass of worms protruding from the body of a cricket
Horsehair worms emerging from a cricket.
Horsehair worms
: These parasitic worms have a multi-stage life cycle that is complicated enough to need some zombies to complete it. Their larvae are laid in water, but they are unable to swim and
need to get to the surface before they can metamorphosize into their next phase. So, they wobble around on the bottom until the more advanced larvae of another insect (like the mosquito or midge) finally eats it. They stay with the larvae as it grows into a flying insect and now they are airborne. They will fly around with this host until it either dies and gets eaten by a cricket or gets eaten by a cricket and dies. And now they are in the cricket, where they will bore through the gut and get into the body cavity (how they do this is very puzzling as they have no mouths). Usually it is only one worm, but as many as 32 have been found in one cricket. It is when they are growing (to about 1 foot long) in the body of the cricket that the mind control begins. At a point known only to the worm, the cricket will be compelled to move toward light and the reflective surface of water. Crickets usually avoid the water and the dangers it carries, but these zombie crickets head right for it and jump in. Once they hit the water, the worms will erupt from the host (to see this in all its grossness, click here). They then immediately mate and begin the cycle anew. The crickets generally die in the water, but every now and then one will survive and take its ravished body back to shore.

Orange Phorid aka Hump-backed fly on a grey tree branch
Phorid or Hump-backed fly

Flies and bees: When it comes to bees, there are two predatory parasites that create “zombees”: In the case of honeybees, phorid flies (Apocephalus borealis), also known as hump-backed flies, use the living bee as an incubator for their eggs. As with other ill-fated hosts, the bee will be consumed from the inside. While this is happening, the honeybee will exhibit most un-bee-like conduct such as flying at night and seeking artificial light. No one except, perhaps the fly, knows why they do this. The bee eventually dies, but the weirdness does not end there. About 7 days later, flies will burst out of the neck of the bee, decapitating the corpse.
Black Conopid aka Thick-headed fly in the air
Conopid or Thick-headed fly

Bumblebees have their own nightmarish zombie maker – the conopid (Conopidae) or thick-headed fly. These flies pry open the body segments of a bee and lay their eggs inside. They are so good at this, that they can do it while both insects are flying. When the larvae inside has grown sufficiently, the mind control takes over. The bee will begin digging in the ground. This is not normally something a bee has any reason to do, but a nice burrow is an excellent place for developing fly babies. And a nice little grave for the helpful host/food supply.

Orange dragonfly sitting on a branch with white spikes protruding all over his body
Dragonfly with a Cordyceps problem
Cordyceps fungi: By now, many people have heard of these terrifying fungi; their effects are nothing short of lurid. In short, the spores enter the host body and force it to climb and move around (this helps further spread spores). Once the host’s nutrient value is gone, the fungus grows stalks that shoot out of the body and further spread their spores. If you haven't seen it, you should watch the morbidly beautiful video of this fungus on an ant from Planet Earth on BBC. This fungus only affects insects and arthropods, but it is so grisly and creepy that it has been imagined as a threat to humans in an apocalyptic video game called The Last of Us by Naughty Dog for PlayStation 3. Check it out here.

Drawing of a zombie woman with white specks protruding from her head. Image from the video game The Last of Us.
Image from The Last of Us
All of the above zombie situations are gruesome and a bit disturbing, but they are simply another part of inherently brutal Nature. It is interesting how we place some insect behavior in the negative category while others are seen as a positive. A number of our most important products here at ARBICO Organics™ are parasites: Fly Eliminators™, Aphidius colemani and Beneficial Nematodes, to name a few. ARBICO would not be here without these parasites, I'm just glad we aren’t in the horsehair worm business!                               

Submitted by Pam

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