Thursday, March 29, 2012

Answer: How long is it?

Image of Ball's Pyramid from Wikimedia.

Yesterday's question had two parts: 
1.  What was the name of the ship that nearly caused the extinction of this amazing insect?  (For extra credit, why would a ship running aground have such a dire consequence?)  

2.  How long is the body of the insect when it first hatches from the egg?  (This is also totally surprising.)  

Most people found part 1 to be pretty straightforward.  A query like [large insect island] quickly leads to the NPR story by Robert Krulwich about the Lord Howe's Walking Stick  that ran just a few weeks ago... unfortunately for me as that article (which is a great story!) made this search a bit TOO simple.  

From the Krulwich report that you can read the story of how the S. S. Makambo ran aground Lord Howe's island in 1918.  If you do a few searches to second source his story, you can find lots of supporting evidence.  (It's not that I don't trust Robert Krulwich, it's just that I check almost everything.)  Rats from the ship went ashore on Lord Howe's island and wiped out the insects pretty quickly.  A sadly common story throughout much of the South Pacific islands--invading species destroys endemic animals and plants.

The second question, though, is a bit more difficult.  

Several readers did a smart thing and used the scientific name of the insect to search for more biological information.  This is a good strategy to remember: When you're searching for detailed scientific data, you usually want to use the binomial version of the name (that is, the pattern is Genus species, the scientific Latinate version of the animal's name).  In this case, it's Dryococelus australis, the Lord Howe's Walking Stick. 

So a quick search for [Dryococelus australis nymph size] (or [... hatchling size]) quickly leads you to the remarkable (and very unexpected) Husbandry Manual for the Lord Howe Island Stick Insect issued by Australasian Society for Zookeeping.  Yes, there are a group of people who have collected all known information about how to raise and keep these insects happily in captivity.  

In that text, the following sentence appears (this has got to be one of my favorite sentences in all the scientific literature):  "LHISI nymphs measure approximately 20mm on hatching, varying between 16-22mm. They emerge from the egg usually underground, and burrow to the surface to climb the nearest large object. If kept in Chinese takeaway containers they will always be found clinging to the underside of the lid."  

And that would seem to be that.  

Except that I (like many of you) also watched the video of the LHISI emerging from its egg case.  And when the operculum on the egg popped open, an amazing large insect emerged.  (Thanks to Rohan Cleave at the Melbourne Zoo for posting that video.)  

I also looked around and since there's a hand in the photo, I can estimate size across the opening hatch at 0.15 inches.  (I later found that the Husbandry Manual tells us that the operculum is 3.6mm wide, which is pretty much the same thing.)  

 I grabbed one of the final frames from the video and measured the insect in terms of "operculum widths."  Each little yellow line in the second image is around 1 operculum width (as estimated from the same image) and then drawn atop the newly hatched nymph.  As you can see, the body is 8 operculums (opercula?) long, and 15 operculums from tip to toe.  If each operculum is 3.6mm, that means the body is 8 * 3.6mm = 28.8 mm (1.1 inches) and overall it is 15 * 3.6mm = 54mm (2.1 inches).  

No matter how you look at it, that's one big insect out of an egg that's the "size and shape of a TicTac."

So... how did you do? 

The average time to solve this challenge was 13.0 minutes; the median time was 10.0 minutes.

But what's always interesting to me (in addition to the amount of time it takes) are the answers we see in the comments.  Here's the distribution of answers given by the commentors.  You can see that we could probably check our work a bit better!   
There seems to be three sources of errors here. 
 (1) Assuming the nymph is the same size as the egg (clearly NOT true if you look at the video);
 (2) misreading the adult length as the nymph length (that's where the estimates of 65 and 75 mm come from);
 (3) eyeballing a length estimate off the image from the video.

(length estimates in mm)

Additional reading:  Gurney, A.B. 1947. Notes on some remarkable Australasian walkingsticks, including a synopsis of the genus Extatosoma (Orthoptera: Phasmatidae). Annals of the Entomological Society of America 40(3): 373-396.

1 comment:

  1. Meet Google's search anthropologist.
    Nice article about Daniel.