The common desert centipede (Scolopendra polymorpha) guards her eggs by coiling her sinuous self around the precious clutch. Illustration by Billings-based artist, photographer and illustrator Louis Habeck.
Happy June, bug fans! Last month’s column explored the world of baby bugs through the lives of two ludicrous larvae, both of which used their butts to some awesome ends. This month, it’s all about the parents.
Compared to what’s expected of human progenitors, insects get off pretty easy, with the bar for good parenting set very low, indeed. After all, arthropod fathers tend to peace out after conception — before the eggs are even laid, while the mothers often abandon their eggs after oviposition.
So when these creatures exhibit even perfunctory parental discretion — laying eggs near food so hungry hatchlings won’t starve, for example — entomologists get all mushy.
“Oh my god, oh my god … that Elasmucha laterallis is guarding her nymphs. Squee!”
“Huh. Cool.”
“Cool? Listen, friendo, long-term maternal care is super rare in insects, and this little bug is guarding her babies like a boss. I’m not sure you appreciate how cute this is…”
“Ugh. Mom-of-the-Year stinkbug. Got it.”
But, despite the relative rarity of parental care among arthropods, examples abound, thanks, in part, to the creatures’ sheer number and diversity. Two such critters in our area include the crab spider (family Thomisidae) and the common desert centipede (Scolopendra polymorpha).
Crab Spiders
Crab spiders get their name from their squat, crablike form and behavior. Like their crustacean cousins, crab spiders use their much longer, often spiny, front legs to capture and hold ambushed prey. The arachnids can also scuttle sideways and have a habit of raising their forelegs over their heads when teased (as crabs charmingly do … snap, snap!).
M.L. Kirst
Flower crab spiders, like this female goldenrod crab spider (Misumena vatia), puncture prey with small, strong jaws; vomit digestive fluid into the victim’s body; and then suck out the viscera. To accelerate the process, the spiders often exploit gravity by raising prey items over their heads as they eat.
Of North America’s 130 crab spider species, Montanans are likely most familiar with flower crab spiders from the genus Misumena and ground crab spiders (genus Xysticus).
The goldenrod crab spider (Misumena vatia) is particularly hard to miss as it’s our largest crab spider and is ubiquitous in meadows and gardens. Their lives are short but sweet; the spiders’ ephemeral existence (most live less than a year) is spent in the scented shelter of Montana’s most beautiful blooms; sego lilies (Calochortus nuttallii) and arrowleaf balsamroot (Balsamorhiza sagittata) come to mind.
Female goldenrod crab spiders are various shades of white or yellow and are often streaked pink at the sides. They’re remarkable, though, for their ability to reversibly change color, from white to yellow and back again, in order to match the blooms in which they wait for prey (pollinators, mostly).
Only the females do this and the change — a complex process powered by the production and destruction of special pigments called ommochromes — takes about three days. What’s more, these pea-sized predators possess small, strong jaws and relatively potent venom (especially to bees, though it’s harmless to humans), which allow them to take down prey many times their own size.
Male goldenrod crab spiders are much smaller (and darker) than the females. These diminutive dudes are best observed when mounted atop the females prior to copulation. It’s a lovely living tableau, as illustrated here by local artist Elley Swan.
Male goldenrod crab spiders look almost nothing like the females (a condition known as sexual dimorphism). They’re about half the females’ size with reddish brown forelegs and a banded abdomen. I often only notice the minuscule males when they’re mounted atop females, which they do to determine the female’s sexual status.
“Um … excuse me. I don’t mean to be rude but are you by any chance … (cough ) … a virgin?”
Ground crab spiders live below this floral fray and so are much less colorful. Their earthy patterns and hues help camouflage the small shy spiders as they hunt prey from hiding spots amidst the earth’s scraps and stones.
And while they differ in habitat and hue, the females of both spiders share a similar parental impulse: guard your babies with your life.
Generally, after mating, male crab spiders depart quickly so as to avoid being quickly departed by the tired and testy females, who switch their focus to egg laying and “brooding” — a maternal behavior in which the moms stand guard during the eggs’ incubation period.
Flower crab spiders lay their eggs on leaves, which are then folded over and wrapped, protectively, with silk. Ground crab spiders, on the other hand, lay their eggs in circular, silken purses that are then attached to the underside of logs or stones. Both then proceed to guard their precious parcels until their own death, which — barring enemy attack or early starvation — usually occurs once the eggs hatch.
I was fortunate to observe this motherly devotion firsthand, during a Montana Master Naturalist field trip to Yellowstone River State Park last month. My job was to scrounge up some cool invertebrates to show the class. So, cue the warm fuzzies when, upon flipping over a rotting log, I spotted two crab spider mamas, each literally clutching her silken sac of eggs to her chest. Overcome with thoughts of my own little “spiderling,” I nearly squeed my pants.
Common desert (or tiger) centipede
Wonderfully, it was during this same field trip that I found (again under a log) another of Montana’s impressive invertebrate parents: the common desert centipede (order Scolopendramorpha).
M.L. Kirst
Scolopendrid centipedes don’t use their last pair of legs for locomotion but, rather, as sensory “feelers.” These antenna-like legs contribute to a back-end that looks strikingly similar to the centipede’s front-end, a modification that scientists believe protects the animal by confusing potential enemies like birds.
These amazing animals can reach lengths of more than five inches (making them one of Montana’s largest arthropods) and, though common, are rarely encountered. This is due, in part, to the creature’s nocturnal habits but also to the fact that, unlike insects and arachnids, centipedes lack a protective waxy cuticle, rendering them highly susceptible to desiccation. Consequently, centipedes are almost always found under things; stones, logs, cow patties (the mighty cow pie: literal shitty shacks for the mini and many-legged).
But, despite its dependence on moist microhabitats, the desert centipede is still one of the top invertebrate predators in its ecosystem, feeding primarily on other arthropods but also — if the centipede is old and big and badass — on small reptiles, amphibians and mammals. Interestingly, centipedes don’t rely on mouthparts for prey capture and venom injection. Instead, they dispatch their dinner using their front legs (insert JPEG of Sonya from Mortal Kombat here), which are equipped with venom glands and modified to act like fangs.
But these formidable beasts have a softer side. When females lay eggs, the mamas protect their young by curling their bodies around the clutch and diligently licking each egg to keep it clean and fungus free.
Bear hugs be damned. It’s all about the centipede snuggle.
Outro
Sadly, with the unfortunate, but understandable, suspension of Last Best News, this is the final installment of BugBytes until the column finds a new home.
I want to thank my fantastic BugBytes’ readers; Adam Rozett for creating our excellent logo; the column’s illustrators — Danielle McCracken, Elley Swan, Logan Hendricks and Louis Habeck — for their gorgeous renderings of various BugBytes’ beasts; and my (super patient) friends and family, many of whom I referenced (or lovingly poked fun at) during the column’s run.
And what a run it was! In three short seasons, we managed to talk about everything from real-life Pokemon, to terrifically fast beetles, to fugitive tarantulas. We even managed to school folks on the art of “Gandalfing,” a useful skill when your bug net is not immediately at hand.
Most importantly, though, I want to thank Ed Kemmick, who believed in and supported this admittedly odd little project from the get-go. I’m so honored that BugBytes found a home with a publication as interesting, well written and locally focused as Last Best News.
Keep buggin’ and, as always, remember: when it comes to insects and their kin, the truth is stranger than fiction!
