The Daily Bucket is a regular series from the Backyard Science group. Here we talk about Mother Nature in all her glory, especially the parts that live nearby. So let us know (as close as you are comfortable) where you are and what's going on around you. What's the weather like? Seen any interesting plants, bugs or critters? Are there birds at your feeders? Deer, foxes or snakies in your yard? Seen any cool rocks or geological features? Post your observations and notes here. And photos. We like photos. :)
A couple days ago I was taking a morning walk at the Sawgrass Lake Nature Preserve near my house in St Pete when I came upon a pair of millipedes. It was a cool and damp morning—perfect for millis to wander around and look for a girlfriend.
Millipedes belong to the group “Diplopoda” which means they have two pairs of legs for every body segment. Colloquially, they are often called “thousand-leggers”, even though most of them don’t have a thousand legs—150-200 would be more like it. They range in size from tiny soil-dwellers only 2mm long (that would be about as long as a nickel is thick) to big African ‘pedes that are 10 inches long and as big around as your thumb. They are a very ancient group, and it is likely that some of the very first land-dwelling animals, over 425 million years ago, were millipedes—attracted by the plants which had newly invaded the land. Today there are around 12,000 known species, with the number of undiscovered and undescribed species likely several times that.
Millipedes lack the waxy cuticle that insects have and they dry out quickly in the sun, so they are limited to habitats that are damp all the time. Typically they are found under rocks or in leaf litter. For that reason, damp dewy mornings are a great time for mating.
When a wandering male encounters a female, he will release a set of chemical pheromones which communicate his intentions, following that up by tapping her body with his antennae. If she’s not interested, she will roll her body into a tight protective coil and rebuff him. If she is receptive, however, he will align his body alongside hers and insert a “spermatophore” into a sperm storage sack in the front of her body, using a specialized pair of legs at the front of his body called “gonopods”. They can remain locked together for several hours.
The female keeps the sperm stored in her body until she is ready to lay eggs. These are laid in damp soil under a rock or inside a rotting log. In many species, Mom will curl around the clutch to protect it from ants. (Most millipedes can excrete weakly-toxic chemicals such as dilute hydrogen cyanide or hydrochloric acid or a variety of alkaloid poisons.) The hatchling millis wander off on their own. It typically takes them a year or two to reach maturity.
Florida has around 50 species of millipede. The ones I see most often are Ivory Millipedes, which are native, and Vietnamese Rusty Millipedes, which are not. The ones in these photos are Greenhouse Millipedes, Oxidus gracilis, which are non-native tropicals that have been spread around the world and got here through the garden trade in potted-plant soil. There were a few of them crawling around on the boardwalk in the morning dew and a couple of mating pairs.
Some photos (the male is the smaller of the two). They were totally oblivious of me and my camera.
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And now it is your turn: what’s doing some afternoon delight in your neck of the woods?
We are always looking for new people to produce Daily Buckets, where we practice "backyard science" by reporting and recording what we have seen in the natural world around us (and no matter where you are--even in the middle of the city--there is nature around you). You don't need any science degrees or training or in-depth experience to be a backyard scientist, and you don't need any expensive camera equipment or photo-editing software to do Daily Buckets. All you need is a pair of eyes and ears, a phone with a camera, and a lot of curiosity and enthusiasm.
