Limes & Science Go Together

In 1740, an English commodore led an ill-fated squadron of ships out to sea, prepared to circumnavigate the world (and attack some Spanish holdings along the way). Of over 1800 men starting the voyage, only 500 survived. The main killer was not war or weather, but  nutrition.

Just a few years after the flotilla returned, a naval doctor conducted one of the most famous experiments in the history of science. After a few months at sea, sailors on Dr. James Lind’s ship began exhibiting signs of scurvy. The doctor treated sick sailors with random supplements to their regular diet. Some shipmen received vinegar, or sea water, or barley water. They made no improvement. Sailors who were given citrus fruits, though, made quick and full recoveries.

Unfortunately, dogma and a small sample size caused many (including Dr. Lind) to underestimate the power of citrus. It wasn’t until the mid-1790s, as scurvy-free anecdotes and experiences grew, that ships rationed out citrus juice to prevent the disease. Enjoy some lemons, limes, or oranges in celebration of science!

Beech Bodies

Take a walk in a winter forest and you can’t help but notice beech trees. Silky smooth bark and sand-colored dry leaves stick out like Christmas lights against a dull and gloomy background. While every other leaf drifted to the forest floor months ago, beech leaves hold tight like cat hair on a sweater.

It’s called marcescence – these leaves that just won’t drop – and it’s common in oak and beech (the trees are close relatives). But why keep the leaves? Are these trees just photosynthetic versions of hoarders?

One possible reason may be to protect that bud, the thin tapered structure often described as “cigar-shaped.” Inside the scaly covering are the beginnings of the new year’s growth. Hungry deer can ruin a tree’s plans for spring. But with beech trees, deer tend to get a mouthful of dry leaves whenever aiming for a yummy bud. (1)

What about attacks from smaller enemies? Insects seem to prefer infesting trees with leaves hanging on over winter.  R. Karban decided to yank all the leaves off a few dozen small oaks and compare infestation levels of a tree-noshing wasp. (2) His numbers indicate that wasps prefer leaf-hoarding trees three-to-one compared to his denuded ones.

I believe Nature is constantly sending messages of wisdom if we’ll just listen. In this case, perhaps she’s saying “every action has an upside and downside, but with diversity, there’s always hope for a better future.”

1. Svendsen, Claus R. 2001. Effects of marcescent leaves on winter browsing by large herbivores in northern temperate deciduous forests. Alces 37(2): 475-482.
2. Karban, R. 2007. Deciduous leaf drop reduces insect herbivory. Oecologia. 153: 81-88.

It’s snowing dinosaurs!

Decorating for the winter season? Here are four unique templates (with educational tidbits, of course) you can download.

• Trilobite snowflake
• Triceratops snowflake
• Tyrannosaur snowflake
• Hadrosaur snowflake

I originally created these for Darwin Day in February – but this kind of joy never goes extinct. Enjoy making these fun flakes!

Winter’s “Toasted Marshmallow” Egg Case

This “toasted marshmallow on a stick” is the egg case of a Chinese Praying Mantis (Tenodera sinensis), containing hundreds of developing youngsters. The eggs overwinter in this protective case until the spring’s warm weather triggers the eggs to hatch into tiny nymphs (mini-mantids). Nymphs grow into adults who enjoy their summer, snacking on any and all insects who cross their paths. In the fall, Praying Mantises mate, lay their eggs, and pass away.

A female mantid’s work may all be for naught if a tiny parasitic wasp interferes. The mantis lays her eggs in a frothy matrix that hardens around her offspring; but this mini wasp (sporting a ridiculously long ovipositor and rear legs that look like the mantids’ front legs) can lay her eggs inside the mantis case before it hardens. Since the wasps hatch first, they’ll use the mantis eggs as food.

Thanks to Mike Dunn (Roads End Naturalist) who recently presented a guide to winter wildlife – tracks, chew marks, and insect sign. Not only was I awed by his amazing photos, Mike also brought samples of all sorts of wintertime insect egg cases (including this one), cocoons, nests, tracks and galls.