Stories tagged caterpillars

It's Friday. Yes, I know I missed it last week. But it's time for a new Science Friday video.

Science Friday
Science FridayCourtesy Science Friday
This week,
"The latest on the bug beat: To survive floods, fire ants band together to form a raft. They can sail for weeks. But how does the raft stay afloat? Researchers report the answer in PNAS this week. Plus, engineers at Tufts are looking to the caterpillar for inspiration for soft-bodied robots. The problem is that squishy bodies make it difficult to move quickly--but some caterpillars have developed a workaround."

It's probably not the worst day in this caterpillar's life: But it's the worst day it will remember.
It's probably not the worst day in this caterpillar's life: But it's the worst day it will remember.Courtesy The Agricultural Research Service
That’s a lie, really—If I suddenly discovered that I had the ability to lay eggs inside a living caterpillar, I would probably have myself sealed in a basement. An eternity of being bricked off in an alcove is probably preferable to an all-encompassing desire to stab an ovipositor into moth larvae.

Unless you’re a wasp. It seems that the world, in its unceasing attempts to gross us out, has come up with something new: a wasp that lays eggs in a caterpillar. That, obviously, is nothing remarkable—all sorts of things stick their offspring in other things. This wasp, however, turns the caterpillar into a zombie guardian of the wasp larvae as they hatch and crawl out of its body. Oh, man! What a trick!

So, the wasp larvae hatch (again, inside the body of the caterpillar), and then chew their way out of its body. Once they’re out, and doing…whatever it is parasitic wasp larvae do (Sega Genesis?), the caterpillar stops eating, remains close to the larvae, and uses its head as a club, thrashing its body to beat away any predators.

I’m sure that all the other little wasplings are super jealous of those who have huge zombie bodyguards, but, more than that, research has shown that zombie caterpillar bodyguards increase chances of larvae survival by 200%.

So, to refine my earlier statement, if I could turn caterpillars into zombie servants, I would. But not if it meant that I had to lay little JGordon eggs in them. Yuck. I don’t think that’s how I was born (although my mother has always been pretty vague on the subject, and my father always refused to discuss it at all).


Monarch butterfly: Image courtesy The Divine Miss K.
Monarch butterfly: Image courtesy The Divine Miss K.
As with the earlier post this question comes from the handwritten questions people leave for our featured Scientist on the Spot. Not all the questions fall into the given scientist’s area of expertise, but are still good questions, so I’m taking a stab at answering them.

This question is particularly timely: “How many days does it take for a Monarch butterfly to hatch?” Timely not only because the migration of Monarchs to Mexico begins in August, but also timely for me on a personal level as one of my favorite places to visit with my mom, wife and daughter at the upcoming Minnesota State Fair is the butterfly tent! (Which, devoted fairgoers, has moved to east of the grandstand on the corner of Dan Patch Avenue and Underwood Street.)

I am assuming the question is really how long it takes the butterfly to metamorphize from a caterpillar to a butterfly. I ask because the caterpillars themselves hatch from eggs. The whole process, from egg to butterfly, takes four weeks. The eggs hatch after 7-10 days, and the process of hatching from the chrysalis takes around two weeks. The length of these stages is impacted by the temperature – the cooler it is the longer this process takes.

Monarch migration patterns: Image courtesy Monarch Watch.
Monarch migration patterns: Image courtesy Monarch Watch.
Now, here is one of the really cool things about Monarchs, I think. Each adult butterfly lives about 4-5 weeks. But once a year in the autumn there is a "Methuselah generation" which will live 7-8 months – effectively outliving the combined lifespan of their parents, grandparents, great-grandparents, and great-great-grandparents. It is this generation of butterflies that migrates from Canada and the United States to either Mexico (if they are east of the Rocky Mountains) or to the Southern California cost (if they are west of the Rocky Mountains – though this population seems to be shrinking – see an earlier post on this).

It is incredible to me that these insects can make a migration that they have never made before, that their parents never made, their grand parents never made, as well as their great-grandparents, and great-great-grandparents. Bryan wrote a post on some recent research that butterflies, “sych UV information up with a natural clock in their brain. By combining these two bits of information, monarchs are able to determine the angle of the sun and always head due south,” which I think is really amazing.

Thanks for the great question!


Every winter Monarch butterflies head south to Mexico to avoid cold temperatures.

monarch butterfly on a branch
Want to learn more about Monarchs and other butterflies? Visit the Science Museum's Monarchs and Migration website

But how in the world do they know how to get there? Well, they don't follow Highway 35, that's for sure. It turns out that monarchs can detect the sun's ultraviolet (UV) rays even when it's cloudy out. (UV rays are the part of sunlight that causes sunburn.)

Up until now we didn't know how butterflies used this UV information to fly south. Researchers led by Steven Reppert at the University of Massachusetts Medical School ran some monarchs through a flight simulator and discovered their secrets. It turns out that monarchs' eyes are very sensitive to UV light. They synch this UV information up with a natural clock in their brain. By combining these two bits of information, monarchs are able to determine the angle of the sun and always head due south. Sailors used a similar method (a sextant) to navigate around the world before the invention of compasses. Monarchs can do the trick all by themselves, though.

Do you think you could walk due south, from Minnesota to Mexico even on a cloudy day?

Some tagged monarchs have travelled more than 265 miles in a single day! Not bad for an insect...

Journey North and Monarchs in the Classroom also have cool websites (complete with projects and "Citizen Science" opportunities) about the annual Monarch butterfly migration.