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.

Parasitic “Bait”

These pulsating, engorged snail tentacles are actually a parasite’s way of moving to its next host. Birds see these juicy caterpillar-like structures and gulp them down.

Inktober Day 3 prompt: “Bait”

Chirpless: Camel Crickets

Camel crickets (Ceuthophilus sp.) enjoy hanging out with humans. Perhaps you provide shelter to some in your garage or basement. These insects lack one major cricket trait though – chirping. Sound production should allow camel crickets to find each other in a dark cave or crawlspace. So, why no chirps?

A Chirp Mystery

One possible reason for the lack of chirps is a high risk of predation. In other species of crickets, those who call more or longer often end up as a snack. ^{1, 2} While I would hope camel crickets are relatively safe from bats and birds in your basement, spiders and mice are the crickets’ major predators. Both possess a solid sense of hearing.

Many crickets have parasites who also seek hosts by sound. Chirps attract female crickets, but they also draw mama parasites searching for a cozy spot to lay eggs. The developing parasitic larvae eat the cricket from the inside, exploding out of its body as they grow. Crickets in areas with these parasites quickly evolve “chirplessness.” Do camel crickets need to worry about these “Alien” chest-bursting scenes? While they do have a doozy of a parasite (an intestinal parasite that weakens the cricket enough to ensure predation), the infections are not related to sound production.

Perhaps camel crickets simply lost their physical ability to chirp. Most crickets produce sound by rubbing their wings together. Camel crickets, though, don’t have wings. In a basement, flying is probably not the most effective means of transportation.

The Scent of a Cricket

So, how do camel crickets find each other without sound? One word: pheromones.

Pheromones are used by many cricket species to indicate dominance, reproductive readiness, and location. Camel crickets release a scent that causes them to congregate. Researchers determined the pheromone is unrelated to reproduction since juveniles move toward the scent too. Nagel and Cade³ think the pheromone prevents camel crickets from drying out. We do know the antennae detect these pheromones. In a rather disturbing experiment, researchers found that camel crickets don’t aggregate when their antennae are lopped off.

 

1. Baily, W.J. & Haythornthwaite, S. (1998). Risks of calling by the field cricket Teleogryllus oceanicus: potential predation by Australian long-eared bats. Journal of Zoology. 244(4) 505-513.
2. Hedrick, A.V. (2000). Crickets with extravagant mating songs compensate for predation risk with extra caution. Proceedings of the Royal Society B 267(1444) 671-675.
3. Nagel, M.G. & Cade, W.H. (1983). On the role of pheromones in aggregation formation in camel crickets, Ceuthophilus secretus (Orthopter: Gryllacrididae). Canadian Journal of Zoology 61(1).

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.