Plants that use pollen to reproduce have evolved strategies for luring in the best pollinators to help spread the pollen while discouraging other nectar-loving animals that are destructive. At the same time, some animals develop their own workarounds to get to the nectar.
Take carpenter bees and the meadow phlox that is growing in two small gardens in my yard. During reproduction, the female bees, which are larger than the males, use their impressive mandibles to chew through wood create chambers in which to lay their eggs. But the mandibles serve another purpose when it comes to accessing nectar in some plants. Some plants produce long, narrow, tubular flowers with nectar at the bottom to lure in butterflies and moths, which have a long, straw-like proboscis to suck up the nectar and hummingbirds, which have long tongues for the same purpose, carpenter bees have neither.
And yet, for years, I’ve seen many carpenter bees on the meadow phlox. This plant’s tubular flowers are wide at the mouth, narrowing to a tube that is only about a sixteenth of an inch wide and up to an inch long. The flowers’ anthers, which carry the pollen, are at the opening of the flower, so any animal trying to reach the nectar must ostensibly brush against the anthers on the way down. The animal will then carry the pollen to flowers they subsequently visit, pollinating them.
I’ve seen tiny bumblebees climbing down inside the top of the flower to try to reach the nectar of the shorter phlox blooms, or maybe these bees are just after the pollen to feed their young. But carpenter bees, especially the hefty females, can’t negotiate the passage at all.
One day recently, as I was observing and photographing pollinators visiting the phlox, I noticed that female carpenter bees, as usual, were buzzing around the phlox. Most crawled over the opening of the blossoms, but instead of trying to climb down inside the flowers to get nectar, they climbed down the outside. Near the base of the flower, they grasped the stem with their mandibles. They were apparently using their large, sharp mandibles to get at the nectar inside the base of the flowers, but they weren’t cutting off the flowers’ tops.
In doing some reading, I found carpenter bees only slit the flower stem to get at the nectar, leaving the flower still able to produce nectar and pollen. Some large nectar-eaters use similar strategies, as I found out coincidentally. I was watching a nature program about Madagascar, which showed sunbirds there using their beaks to puncture flowers at their base and get the nectar.
Carpenter bees still help the phlox with pollination. Females collect pollen, forming it into pellets on which to lay their eggs, providing a ready buffet when the larvae hatch out. According to a U.S. Forest Service article, the bees use “buzz pollination” to do this. When they land on the blossoms, they use powerful muscles in their thorax to become animated “tuning forks,” creating ultrasonic vibrations. The vibrations shake loose the dry pollen grain. That helps explain all the buzzing and crawling around on the flowers’ the bees do before aiming for the nectar — the bees are “sonicating” the pollen. With the anthers being about even with the outside edge of the flower, the bees also likely collect the pollen just brushing across them.
Insects can go to other extremes to get a nectar. I recently found a spicebush swallowtail butterfly halfway up a hosta’s dropping, tulip-like bloom, trying to get at its nectar. I’d never seen a butterfly go so far into a flower, but butterflies, like many insects, can get into tight places, including human ears.
In thinking about the determination of the carpenter bee and the spicebush swallowtail in reaching their goals, I was reminded of a plant I had read about in Science Daily. The plant in question is a nicotiana (tobacco) species that shifts its strategy for luring in harmless potential pollinators while discouraging a harmful one. In this case, the harmless pollinators were hummingbirds, who were attracted by the blossoms’ scent, but a moth whose caterpillars fed on the plant was also attracted to the scent.
Researchers studying the plant’s strategy found that, when it is being attacked by the moth’s offspring, the plant changes the opening time of its flower buds from dusk to dawn. Instead of the nocturnal moths, these morning-opening flowers attract diurnal hummingbirds, “which are also able to transfer pollen — without threatening the plant's life.” This change in flower timing was elicited by specific molecules in the oral secretions of the larvae. The plant also dramatically reduces the emission of flower scents to keep away the herbivorous larvae.
This is just a tiny drop in a big bucket of strategies plants and animals use to get what they want from each other.
© 2019 Pam Owen
Got a bug in your ear?
Butterflies are among the many bugs that can occasionally crawl into human ears, ostensibly to seek shelter. The strange-looking earwig got its name from the myth that they get into our ears on purpose, to lay eggs in there, even drill into our brains. But these harmless insects got a bum rap and are no more likely than most bugs to crawl into an ear for shelter, although they and cockroaches do like warm, damp places. Female earwigs, unlike most insects, will protect their eggs and young from predators.
The pincers (cerci) at the end of an earwig’s body, which are larger in males, are used primarily to protect themselves from predators and capture prey. While they may be daunting to small predators, they only deliver a mild pinch when handled by humans, and generally only when the earwig feels trapped.