Fattest Animal

This cutworm moth (Family Noctuidae) is the fattest animal in the world. In just two summer months of feasting on flower nectar, the migratory moths balloon from 20% to 80% body fat (1). Storing this much energy has a price though – no romance. Migratory moths put reproduction on hold to save up energy for their journey.

Thanks to all that fat, cutworm moths are a major food item for grizzly bears in the summer (2).

It got me wondering: These moths delay reproduction so they can migrate, but putting on fat makes them more delicious. Why not just stay put and make some babies instead? Since their migration is basically east-west, major temperature/seasonal shifts don’t require the move*. Local plants (food) don’t require the move either **. Parasites might. Army cutworm moths are highly parasitized. Moths with parasites stay in the Rocky Mountains longer, growing larger and fatter. So the bears may do the whole population of moths a favor by culling those with parasites.

* Altitude is a factor in temperature and season. But if moths stayed near the mountains, they could stay put moving up and down in altitude without flying a few hundred miles to and from the plains.

** Larvae eat a wide range of leaves and stems. Adults suck up flower nectar. So a large number of larvae may reduce some food for the adults.

1. Kevan, PG and DM Kendall. 1997. Liquid Assets for Fat Bankers: Summer Nectarivory by Migratory Moth in the Rocky Mountains, Colorado, U.S.A. Arctic and Alpine Research 29(4):478-482
2. French, SP, MG French and RR Knight. 1992. Bears: Their Biology and Management. p 389.

The Firefly and the Apes

An old Philippine folktale pits a firefly against a troop of apes. One day, an ape asks the firefly why he carries a lantern. The firefly replies that he uses the light to see mosquitoes and defend himself. The ape laughs and calls the firefly a coward. Insulted, the insect challenges the ape (and all his friends) to a fight. The next day, the firefly faces 1000 apes with large clubs, all lined up against him. The firefly lands on the first ape’s nose and the second ape swings his club to squash the insect. But the lightning bug flits away and the ape’s blow kills his companion instead. Then the firefly alights on the second ape’s nose. A club is swung and the second ape is dead. On and on until the firefly reaches the last ape, who piteously surrenders. The folktale ends, “Since that time, the apes have been in mortal terror of the fireflies.” (1)

Despite folktales consistently portraying apes as fools, we all know they’re actually pretty smart. The Philippine tale is one account of why apes avoid fireflies. But could there be a biological reason for this aversion? Maybe it’s because fireflies are noxious.

One firefly can kill a bearded dragon (Pogona sp.), a fairly large lizard that can grow up to 2 feet long (2). For mammals like apes, well, they probably just taste really bad. Most animals that eat fireflies spit them out or throw them up.

Fireflies do try to warn their would-be attackers through their coloration. Light and dark stripes and red markings are examples of aposematic coloration – both are found on this lightning bug. Don’t say he didn’t warn you!

 

1. Millington, WH and BL Maxfield. 1907. Visayan Folk-Tales. Journal of American Folklore. 20(79) 311-318.
2. Knight, M et al. 1999. Firefly Toxicosis in Lizards. Journal of Chemical Ecology. 25(9)

Bee Bandits

Flowers need bees. A bee’s job is to move pollen from one bloom to another; plants pay for the bee’s service with sweet nectar. Cunningly, some bees have found a way to get a paycheck without the work.

Carpenter bees (Xylocopa sp.) exhibit a behavior called “nectar theft.” Rather than reaching the base of the flower through its opening (and getting a pollen dusting in the process), robber bees bite a hole in the base of the flower to slurp up nectar, bypassing the pollen-yielding anthers entirely.

We can’t necessarily blame them though, as it may be the plant’s own darn fault. Flowers with long tube-like bases are more likely to get robbed since the brawny carpenter bees can’t reach the nectar any other way (1). This relationship may even keep the flower tubes shorter over evolutionary time, since short flowers are more likely to be pollinated (and less likely to be robbed).

In order to deter break-ins, some flowers have evolved thicker flower walls, new toxins, or even special relationships with animal “special forces.” Some tropical flowers produce extra nectar in a special chamber for ants, who act like police in stopping the robber bees (2).

P.S. The bees I watched for this sketch were upstanding citizens – no thievery going on here!

P.S.S. It’s a girl! This bee’s got a black face. Males have a large patch of white on their faces. (http://www.uark.edu/ua/arthmuse/carpbee.html)

1. Navarro L and R Mendel. 2009. Relationship between floral tube length and nectar robbing in Duranta erecta L. (Verbenaceae). Biological Journal of the Linnean Society. 96 (2) 392-398.
2. Gerling D, HHW Velthuis, and A Hefetz. 1989. Bionomics of the Large Carpenter Bees of the Genus Xylocopa. Annual Review of Entomology. 34:163-190.

 

Summertime Blues

Dragonflies hover, swoop and twirl but never walk. They use their legs to trap their insect prey in a tiny six-barred prison before devouring them head-first. When guarding its territory along the water’s edge, this Blue Dasher (Pachydiplax longipennis) grasps a reed or blade of grass and waves his blue abdomen as a warning for other males. Females, in general, aren’t blue at all; they’re black with yellow lines running down their bodies While the name “dragonfly” may be confusing, other names – “snake doctor” or “devil’s darning needle”, for instance – are equally perplexing. No, dragonflies do not treat ailing snakes (or bring them back to life) and the insects don’t sew up any parts of you (although my Grandmother convinced me not to lie with the threat that dragonflies would sew my lips shut if I did). And in case you were wondering about that species name, it means “long wings”… not what you were thinking.