Moth Madness

Adult moths live much like many college students in that their lives revolve around sex. During their very short existence, their only imperative is to reproduce. To this end, they have a streamlined chemical communication system. The female moth produces a unique chemical compound which is known as the sex pheromone. This arousing perfume is produced in glands in her rear end in extremely minute quantities (picograms (10^-12 grams) per hour). The male's antennae are attuned to this odor and can sense her pheromone from afar. Like a bloodhound, he homes in on the female. Actually, the male locates the female by following her scent upwind. No need to even be able to follow a concentration gradient or make interesting small-talk. It's dead simple.

Once male finds female, close-range signals such as compounds present on their cuticles can tell the moths something about each other and their qualities as a mate. When you don't live long, though, it doesn't pay to be picky. The response of male moths to sex pheromones is so predictable, sex pheromones are a great way to control pest moth species without pesticides. A trap like the one in this picture uses an artificial lure imbued with sex pheromone. Males are attracted to the trap, but instead of finding a lovely lady, they find a surface covered in killer sticky slime.

Another way of controlling moths with sex pheromones is a method known as mating disruption. The sex pheromone is often loaded into little plastic tubes like this one that can be hung from trees. Sex pheromone produced by the real moths will be mixed with synthetic pheromone being produced by scads of tiny plastic tubes. Flooding the whole area with sex pheromone makes it very hard for males to locate females. Even when they do manage to find the odor source, a bit of plastic is a poor reward for following a odor plume.

The simple sex pheromone communication system of moths does not constitute a language. But while simple, it is extremely effective, providing a reliable, low concentration, long-range signal requiring minimal energy investment for either the sender to produce or for the receiver to interpret. Moths need no online dating service with its 29 dimensions of compatibility. They already have a language tailor-made for fast and easy hookups.

Pheromone dispenser photo by Eugene E. Nelson, Bugwood.org, used under a Creative Commons License.

Honeybees - starting at the end

When starting a lecture on animal communication, most people would probably leave the honeybees for last. Only because their communication has some unique linguistic features most other animal communication lacks. Namely: symbols. Honeybees have an elaborate language for communicating the location of food and shelter through dance. We have decoded most of it due to the Nobel Prize-winning work of an Austrian named Karl von Frisch.
(Herr Dr. von Frisch looks great in lederhosen, don't you think?).
Karl von Frisch discovered that European honeybees (Apis mellifera) could communicate the precise location of a resource by dancing.
(Can you imagine anything more wonderful? What if we communicated through dance alone? Tell me that doesn't sound like fun.)
The dance has two components: an angle and a distance - all the bees need to find a location. The angle is communicated by the angle at which the bee takes a waggle run relative to straight up. Outside, this angle corresponds to the angle of the resource relative to the sun. The length of time the dancing bee spends waggling corresponds to the distance to the food resource. When a forager bee comes back from collecting food, she will dance, and in the dark hive, other bees will surround her and follow her dancing movements repeatedly, extracting the location information from her movements. Then the foragers will set out to the location she indicated. This is the basic formula for the dance language. Other aspects, such as sharing nectar samples, floral odors, and vibrational signals also play a role in telling the other bees the type and quality of the food resource.

The dance language is also used when a swarm (a newly budded bee community ready to start their own hive) needs to find a hollow cavity to nest in. Scouts that find a suitable cavity dance to communicate its location to the other workers. The better the cavity, the longer a bee will dance for it. This length of time spent dancing is key to the collective decision-making of the swarm, which must take off all at once and move together if they are to survive. The longer a bee dances for a location, the more recruits she will get to check out the possible new home, and the more bees will come back to dance for that location. Eventually, almost all the scouts will be dancing for the preferred location. Once they have reached a quorum, the bees take off to colonize the new home.

So that's the fantastic story of the honeybee dance language. My question is: why so sophisticated? Why do honeybees alone among invertebrates demonstrate use of symbols? Why are honeybees considered the pinnacle of insect communication? Honeybees themselves are not very remarkable insects. Physiologically, they are similar to their bumblebee and wasp brethren in brain capacity. One thing that they do have that many other bees and wasps lack, however, is eusociality.

Eusociality is the term we use to describe social animals where there is:

1. Reproductive division of labor - some individuals reproduce while others give up or delay their own reproduction
2. Overlapping generations - individuals from previous generations live together with individuals from the current generation
3. Cooperative care of young - non-reproductive individuals rear other individuals' offspring

Only a handful of animal species fit this definition. In many ways, honeybees wrote this definition. A single queen bee lays all the eggs in the hive, while the workers (sisters and offspring of the same queen) do all the work of gathering food, feeding the young, constructing, maintaining, and guarding the nest. The honeybee hive functions as a super-organism, with each individual doing its part to serve the hive. The critical phase in the reproduction of this super-organism is the swarming stage, when the hive buds, and a group of bees and a queen must choose a new nest. For the European honeybee, which requires a suitable cavity, this selection process is very important to deciding the future fate of the swarm. You could imagine that the selective pressure would be extremely high for an efficient way of communicating the location of a possible new nest site.

This is only one theory that might explain the evolution of such complex behavior in honeybees rather than other species which do not exhibit swarm-founding. Indeed, the selective pressure for more advanced communication must increase with increasing levels of cooperative behavior. Is this true? Do we find other examples in the animal kingdom of advanced communication in conjunction with cooperative behavior?

Animal Linguistics Series

My linguist friend has invited me (ok maybe I volunteered) to give a guest lecture to her class. In this lecture, I will cover a number of examples of animal communication and compare and contrast these communication systems with those of humans.

Linguistics has always seemed very interesting to me. I might even classify myself as a word geek. I collect new words like shiny insects, pinning them down by using them often. I am very good at crosswords.

Communication in the animal and particular the insect world, however, is rarely possessed of such nuance as actual words. Nevertheless, animals say a whole lot with chemical, sound, and visual signals. Some animal communication systems are surprisingly complex.

To prepare for this lecture, I'm going to go through a few outstanding examples of animal communication over the next several days. Enjoy!

What is a cockroach?

Green cockroach (Panchlora sp.?), originally uploaded by pbertner.

This is a cockroach, order Blattodea. Insects in the order Blattodea (or Blattaria if you're old-school - either way it's a roach) are characterized by long, slender cursorial (running) legs with which they achieve impressive speeds. The top of their first thoracic segment (aka the pronotum) extends up to cover their heads as a shield-shaped hat. Their mouths contain a pair of plain, sensible mandibles for chewing, their 30+ segmented antennae are thin and sensitive, ranging far ahead of their body to warn of impending danger as they run. In those cockroaches that have wings, the first pair is thickened, leathery (they're called tegmina), protecting the hind pair that is thin and membranous.

Many cockroaches are earth-toned: dull brown, tan, red, and black. A few, like the beautiful cuban cockroach (Panchlora nivea) pictured above, have striking coloration.

One thing a cockroach is not, however, is fancy. You will never find them trying to stand out with flashy patterns. They are meant to blend in with the background. Flat bodies, shielded heads, leathery forewings, the body of a cockroach is made for sneaking into small hiding places and for furtive avoidance of malicious predators. Their beauty is a functional one.

Confessions of a Cockroach lover

MMMHHhh tasty water!

I have a confession to make. I am not afraid of cockroaches. I know, I should be. They carry diseases, they cause allergies, they're icky and run too fast. All of which, in any normal human being, should be cause for alarm.

But I just can't do it.

Why? Because they're just doing their jobs - fulfilling their cockroachy calling. Allow me to explain.

Living things are messy. It's true. We secrete and excrete and shed everywhere. When we eat, we always leave crumbs and sticky smears behind. Then we go and die and leave our messy bodies behind. Someone has to pick up the trash. A lot of times, that someone is an insect. Dung beetles specialize on picking up our crap. Ants will happily take our crumbs and lick up our sticky residues. Flies specialize on cleaning up our dead flesh after we've left this world. Cockroaches aren't really specialists. They are the garbage-men. You put it out, they pick it up.

We humans have taken messy up to a whole another level. We have made certain choices to live certain ways that create a lot of garbage. This garbage is typically a mixture of components, bits of organic matter hidden in pockets of inorganic containers and structures. The inorganic stuff is pretty useless to the rest of the living world (not entirely useless, but requiring a great deal of time and energy to return to a useful state) but the organic stuff someone can always use for food. But then who's going to go and extract it? What garbage-man would come into your house and take away all your crumbs from under the fridge? Lick our your yogurt containers, scarf up the stale cookies in your pantry, and clean the slime that clings to the inside of the drainplug in your tub? Cockroaches, that's who. They're the most effective garbage-men ever.

Their all-encompassing garbage-picking skills is what makes cockroaches susceptible to contamination by various nasty microbes. These valiant trash-men don't mind exploring your toilet brush and then your kitchen counters for delicious morsels. 'Clean dish' and 'dirty dish' is not a distinction that they know how to make. So the problem with cockroaches isn't so much the roaches themselves, but the microbes they accidentally pick up when they're on clean-up duty.

Funny thing about those microbes, though- they were already hanging around. In most cases, they were as close as your bathroom floor and your sink. The cockroaches just moved them around. Cross contamination: it's the worst kind of cooties.

So how do you keep the cockroach garbage-men on the curb? Keep your trash there too. Clean up after yourself, and the cockroaches won't have to come and do it for you.

Coco plums

Coco plums, originally uploaded by allspice1.

It's a hedge, it's a tree, it's a delicious edible fruit! It's a Coco Plum! Next to Palm and Pine it is also probably one of the most over-used obligatory plant-name/business-monikers in the tropics. Seriously, there's a resort in Belize, there's a Beach and Tennis Club in Key West, and an appliance store in Vermont (?) that all get higher google ranking than the wikipedia article about the plant.

But it shouldn't be so. It's a very nice plant, Chrysoblanus icaco. All over south Florida, every well-groomed native planting and every scrubby wetland ecosystem is bursting with this attractive, round-leaved native plant.

It has two varieties- an upland and a coastal type. In the picture above you can see the fruit of the upland type. This coco plum can become a bushy tree up to 10 feet tall, bearing dusky purple fruits and dark red growth tips. The coastal type, on the other hand, grows shorter, maybe three feet tall, its new growth blushing only slightly, and its fruits a soft white to pinkish-purple as below.



As my parents and I strolled through a coco plum corridor in Apoxee Park, I squeezed the soft white and pink fruits, wondering how they would taste, but uncertain if their attractive, smooth skin hid poison beneath. My grandmother came to visit us for Thanksgiving and encouraged me to taste the upland variety on another hike. The dark purple fruits turned out to be mostly seed, with a thin layer of white bread-like pulp, dry but sweet. It retreated from my bite, mashed into a shiny white mold of my front teeth. The dark eggplant skin was thick and a little rubbery. I found myself disappointed that I couldn't find more juice in them.

Powering the Cell: Mitochondria

Yay cell biology!