Tuesday, February 12, 2013

Zombies Do Exist!


I recently saw my MSN scrolling news headlines stating that zombies are not real. Oh come on, does the author of that article know nothing. Zombies do exist they just aren’t the decomposing, foul smelling, brain eating former humans that we all know and love from the movies. They are hornworm caterpillars, aphids, sawfly larvae and many more insects!  

My two favorite insects, the Ichneumonid and Braconid wasps, are responsible for many the zombies running around.   If you have ever been fortunate to come across the largest Ichneumonid wasp (Megarhyssa atrata) you probably thought to yourself “Holy crikey! What is that!” Female wasps, like the one below, have a huge ovipositor (an organ for laying eggs) which can be up to three inches long!

 
Scientists aren’t quite sure how the female finds her zombie victim, a horntail wasp larva, it maybe through chemical smells given off by the larvae or she may be able to sense its vibrations as it moves under the bark of the tree. Once she has located her victim she sticks her giant ovipositor into the tree piercing the horntail wasp larvae and laying an egg on the larvae.   

The female Braconid wasp is not as cool looking, but anyone who has planted tomatoes in their garden has probably seen some future zombie crawling around.
 
 
Braconid wasps will lay eggs on tomato hornworms, the larval form of the hawk and sphinx moths. You’ll often see big cubby green caterpillars on tomato plants with little white ovals sticking out of their backs, those are the wasp eggs.  
 

Once both wasps eggs hatch they go to work eating their victims alive. The wasp larvae start by eating their victim’s fat deposits then their guts.  If you see one of these zombies crawling around, which they can as long as the wasp larvae has not eaten their nervous system or their heart, you can see the wasp larvae crawling around under the skin of the caterpillar. This rather gross process goes on until the wasp larvae are just about to pupate. Just before the wasp pupates is kills its victim consumes what’s left of the caterpillar’s gooey insides and then chews its way out and creates a cocoon somewhere nearby.   

So yes zombies do exist and they may be living in your backyard!    
 
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