The BugLady is working up to a BOTW about web-spinning (spiders are not the only practitioners), but this episode is inspired by an amazing flight of spiders that she witnessed a few days ago at Horicon Marsh in Central Wisconsin.
It was the kind of day that gives October a good name – 60 degrees, clear, still. As our intrepid band walked out onto the floating boardwalk on the northwest edge of the Marsh, we were struck (both literally and figuratively) by the webs hanging from the posts and ropes that make up the boardwalk’s railing. Soon, we were webbed, too – imagine the sensation of breaking through spider webs, but imagine it out in the open, over water. We noticed that each of the posts was topped by a mixed bag of dozen or so tiny-to-smallish spiders and that silver streaks of web could be seen in the air at all altitudes. It was awesome, by any meaning of the word.
A spider egg mass may hold several hundred eggs, and when it hatches, each spiderling is elbow to elbow with hungry, competitive and often cannibalistic siblings. Best to get out of Dodge, and why walk when you can fly? Most species of spiders have the ability to produce web, and they can deploy a number of different types of web, depending on the occasion. Web, which starts out as a liquid, is released through “spigots” from spinnerets on the abdomen. As the liquid hits the air, it “solidifies” into the familiar silken web.
When the weather conditions are right (warm enough for thermal updrafts but not too windy), young spiders and even adult spiders of the smaller species climb to the top of a tall object (a blade of grass is tall to them), face into the wind, stand on their tiptoes, and release one or more fine strands called gossamer. Etymologists please note, “gossamer” is apparently a corruption of the Old English term “goose summer” and refers to the warm days in the fall of the year when (pick your favorite, but not-mutually-exclusive, bit of folk lore) geese were eaten and/or goose down is drifting in the air. Thermal updrafts pick up the line – and the spider – for a trip that may span inches or hundreds of miles. Though scientists call it “dynamic kiting,” the process is popularly known as “ballooning.” Spiders have no control over when or where they land, but if it is a favorable spot, they will mature to adulthood the following summer.
From an on-line site called “Journey North” comes a delightful article called “Plankton in the Sky? – Observing Aerial Plankton.” In it, the author points out that a variety of tiny arthropods “drift through the sky in the same way that plankton drifts in the ocean” (a fact that is well known to dragonflies and to nighthawks, swallows, and other birds that feed on the wing). Apparently, a large percentage of these aeroplankton are spiders.
The author goes on to say that “one entomologist, Dr. Gilbert Waldbauer, calculated that during daylight in May, a volume of air one mile square extending from 20 feet above the ground to an altitude of 500 feet contained 32 million arthropods! He wrote that ‘This amounts to 6 arthropods per 10 cubic yards of air. Ten cubic yards is quite a small space, about the size of a small clothes closet.’” Check out the full article at http://www.learner.org/jnorth/tm/spring/Aeroplankton.html
(the author suggests that we put a fine net on a tall pole to sample the day-flyers, and that at night we go outside and shine a strong flashlight into the sky and appreciate the specks floating by.
Spider movements are noted by scientists, agriculturalists, and poets alike. Farmers recognize the value of the insect-control services that spiders provide and want to know how to get them back into the fields after harvest. Charles Darwin, during his cosmos-shaking voyage on the Beagle during which he collected evidence verifying the forces of natural selection, marveled at the spiders that parachuted onto the deck of the ship when it was many miles from shore. Spiders have been collected by traps on airplane wings at altitudes of 15,000 feet.
Anna Botsford Comstock, in her wonderful Handbook of Nature Study (first published by the Cornell University Press as a courtesy, because her husband was head of the Entomology Department and still in print a century later) likens spider ballooning to the way thistle and dandelion seeds disperse. Scientists have studied whether forest spiders use ballooning to disperse as much as open field species do – wind speeds get knocked down considerably inside forests, and most forest plants do not send their seeds out onto the air currents. They discovered that forest spiders do balloon, though body size may be a limiting factor.
For years, scientists misinterpreted the physics of spider flight by using a flawed model in which the web “balloon” was rigid. More recent experiments testify to the elasticity of the balloon, find no correlation between the length of the gossamer strands and the time/distance traveled, and quantify the amount of convection/stability/cloud cover of the atmosphere relative to body size. In one study, the scientists’ math-ridden conclusion was that they had demonstrated “for the first time that optimal conditions for ballooning distance also explain the observed patterns of spider take-off events” (information that, no disrespect intended, folks, even the smallest spider comes equipped with).
Spider flight is a phenomenon that keeps inspiring study, and information about the conditions that result in the maximum dispersal of spiders will help predict the routes of airborne seeds, pollens and pathogens alike (there’s some weird stuff in the dust that blows over the Atlantic from Africa). BugFans will be happy to hear that spiders infected with Rickettsial bacteria – typhus, Rocky Mountain spotted fever, etc – are fit to balloon but are less likely to balloon. Apparently the bacteria don’t want to disperse (“ScienceDaily,” June 18, 2009) (no, people don’t get these diseases from spiders, and the article did not suggest that they are vectors).
Occasionally, movements are large enough to make the newspapers, and some years ago, some Californians were sure that the silvery material (gossamer) they saw in the air came from UFOs.
For a reality check, read chapter XXII: A Warm Wind in Charlotte’s Web.
Most people don’t like aphids, and they get “creeped out” when they hear the word “lice.” Barklice are not related to aphids, though barklouse congregations are sometimes mistaken for aphids. Barklice (family Psocidae) (“so-ci-dee”) are in the same order, Psocodea (“so-so-dea”), as booklice and as the sucking and chewing lice (older references list them as Psycoptera), but the barklouse is a more wholesome-looking bug than its shiftier cousins, and its lifestyle is dramatically different. The BugLady photographed this barklouse (Cerastipsocus venosus) (probably) thinking it was some kind of plant bug, but her bug guru, Chris, rode to the rescue once again. It takes a village.
Psocodea is a small order of small insects – about 62 species of barklice reside in North America. Barklice are small, chunky, big-headed, “bug-eyed,” long-antennaed insects, many of which have four wings. The front set of wings is longer than the rear set, and the wings are held tent-like over the body at rest. The wings of BLs have very few veins and cross veins, and in Cerastipsocus venosus (Cv), these veins are often white. Although they can fly, they prefer to run when disturbed. At about ¼” long, Cerastipsocus venosus is on the heftier end of the continuum; females tend to be larger than males, and there can be a lot of physical variation within a species.
How can you find one? Cvs are relatively common in the eastern half of the country and are often found on the trunks of smooth-barked trees (Cerastipsocus venosus likes the maple family, which includes the box elders). Because many BLs live in leaf litter or under loose tree bark, they generally pass their days unnoticed, as they have done since the Permian Era, some 250 million years ago. The more gregarious species attract notice when a bunch of them gather in a dense “herd” on tree bark, a habit that gives them the names “bark cattle” and “tree cattle.” Other species are web spinners, producing silk in glands in their mouth. They may cover a section of tree trunk with a patch of web or enclose the truck or branches in a silken sheath.
When a young BL’s Fancy turns to Love, it may engage in a courtship dance, after which she accepts a spermatophore (liquid, in the case of Cv) from him. But many psocids reproduce parthenogenetically, which means that Ms. Psocid needs no assist from Mr. Psocid to produce little Psocids. Reproductively speaking, Cvs have an odd chromosome that doesn’t divide like the rest in early meiosis (the BugLady is confident that BugFans remember meiosis and those microscope slides with chromosomes dividing and heading for opposite poles). Half of the secondary spermatocytes, and therefore half of the spermatozoa, down the line, have an extra chromosome. Don’t ask the BugLady why.
BLs practice Simple (Incomplete) metamorphosis. Bugguide.net has a great picture of the pudgy, striped nymphs at http://bugguide.net/node/view/424879/bgimage. Web-spinning BLs deposit their eggs on bark, singly or in bunches, and cover them with a layer of silk. All generations in a colony will live under this shelter briefly and then, apparently, will eat it. Cvs protect their egg clusters with a crust of what several sources delicately call “alimentary excretions.” It takes about 6 molts for nymphs to reach adulthood, and they probably overwinter as eggs.
Despite home-owners’ fears when they see a crowd of insects on their trees (eliciting headlines like “Tree cattle causing undue concern”), neither the adult nor the immature Cvs eat trees, leaves or even bark. They use their chewing mouthparts to graze on tiny plants like algae and lichens and on molds that grow on the tree bark substrate, or they scavenge on pieces of organic material (detritus). To this end, part of a BL’s “lower jaw” (maxilla) is modified into a rod that the insect uses to brace itself while the “upper jaw” (mandible) is scraping up its food. They are listed as scavengers/decomposers. Birders please note - one source mentioned that Chimney Swifts catch and eat adults when both are on the wing.
The BugLady is troubled by a website called “Invasive.org; Center for Invasive Species and Ecosystem Health.” whose sponsors include several Federal agencies and a few departments of the University of Georgia. Their site comes up on her searches with some frequency, even when the insect she is researching is not considered harmful. There is a page devoted to PL images, but no allegations of damage – even the Exterminator sites say “these bugs are harmless; if you don’t like the webs, spray them with the hose.” Like Exterminator websites, this site gives even the “neutral” bugs a bad name by association (the BugLady tries not to assign pluses or minuses to bugs).
This week’s episode features a Bevy of Beetles. Beetles are in the Order Coleoptera, which you Latin and Greek scholars know means “sheath wings.” Their pair of membranous, flying wings is covered at rest by a top second pair of wings (the elytra) that protects them, but because the elytra have to be held out to each side in flight, they fly awkwardly.
With antennae that may be twice as long as their body, the Long-horned beetles (Family Cerambycidae) includes some elegant-looking beetles. The Family includes many species with names like “borer,” (stump, root and bark, but NOT the infamous Emerald Ash Borer which resides in a different beetle family), “sawyer,” “pruner,” and “girdler,” so we know what they are up to in their spare time and why some species are so unpopular with the timber industry. For the same reasons, they are important players in Mother Nature’s recycling program. The larvae of many species rummage around in trees and shrubs, living or dead, often leaving characteristic trails in the wood, under the bark. According to Kaufman, in the Field Guide to Insects of North America, others girdle a twig or small branch and lay an egg in the groove; when the grub hatches, when the grub hatches, it eats now-dying twig that its mama provided. Some long-horned beetles “vocalize,” producing a squeak made by friction when they nod their heads. “Lng hrnd beetle 9” (who might possibly be Centrodera decolorata – many insects do not have common names) is about 1 ½ inches long, excluding its antennae.
The Bug Lady has photographed hundreds of insects and has never been bitten/stung in the course of taking their portraits, but she won’t touch this beauty, found on goldenrods during the month of August (and we’ll discuss ants at a different time…). Blister beetles produce on their persons an irritating substance called cantharadine, once used as an aphrodisiac. If you touch them, you'll get a dry, itchy blister that will last about a week. They are identified by their velvety appearance and the fact that their elytra (ee-lee'-tra), the hard, modified forewings that cover the softer, folding flying wings, are somewhat shorter than the abdomen.
Despite the efforts of TV advertisers to sell you natural tranquilizers made of St. John’s-wort, the plant is not welcome over much of its range. St. Johns-wort is a sun-loving, alien invasive plant that loves road edges, fields and pastureland. When cattle (and susceptible people) eat it, the incomplete metabolism of its pigment dots results in chemicals being deposited just under the skin layer. That causes the consumer to become extra sensitive to the sun’s rays and to burn easily. Klamathweed beetles are alien beetles imported as a biological control of St. Johns-wort on western grazing lands (they seem to be moving east), and from what the BugLady has seen in her fields, they do an effective job on it. The BugLady, however, has reservations about the concept of introducing one foreigner to eat another foreigner, as in “No worries, Mate - when it finishes eating the __(fill in the blanks)_ it won’t move on to anything else…….”
Beetles are the largest order within the Class Insecta. Every fifth living thing (not every fifth INSECT, not every fifth ANIMAL – Every! Fifth! LIVING THING!) is a beetle.
Today's bug is the ubiquitous and very unassuming aphid. Aphids are Homopterans (No, the Bug Lady is not being any more politically incorrect than usual – aphids belong to the Order Homoptera (“same wing”), which also includes the cicadas, treehoppers, leafhoppers, aphids and scales). Some enthusiastic entomologists lump the Homoptera with the nearby Hemiptera, or True bugs. Aphids come in a variety of colors (aphid green and aphid yellow and aphid red are popular) and, and with their small heads and large abdomens, they look a bit Shmoo-ish.
1.) So many mouths to feed – what do they eat? Plant juice. Lots and lots of plant juice. The majority of aphids are picky eaters who are attracted to a particular plant species or family. Aphids stick their little beaks into a plant’s soft tissues and start drinking. Entertaining a few aphids won't compromise a plant, but hosting a whole battalion can damage the plant or impair the production of seeds. As an aphid feeds on plant sap, it excretes the unneeded portion in the form of small drops of honeydew which, according to Donald W. Stokes in A Guide to Observing Insect Lives, it normally flicks off of its abdomen. Wasps, butterflies and flies feed on the droplets that fall on nearby leaves.
Some species of ants "farm" aphids; they protect their chosen flock of aphids by chasing away enemies like ladybugs and lacewings, and carry the aphids to new feeding areas. They "milk" them by stroking the aphid’s abdomen, which results in the aphids giving off a drop of honeydew for the ants to ingest. Stokes says that aphids that are farmed hang onto their honeydew longer and so produce larger droplets when they are milked, and that the farmed aphids produce more offspring. Ecological relationships that benefit both parties are called “symbiosis.” The BugLady sees these interactions on her highbush cranberry in mid-summer and on burdock in late summer; sometimes the ants will make so many trips to the aphid-bearing plant that they will wear a trail on the ground.
The uniform, circular holes in the empty aphids in “Golden aphids, punctured” were not produced by the mechanics of molting, as aphids popped out of their old skins and flew happily away; they are the work of parasitic wasps with full stomachs.2.) How do Big Aphids make Little Aphids? Aphids practice "Simple" or "Incomplete" metamorphosis – the young pop out, without benefit of eggs in the case of aphids, resembling their old lady, needing only to grow a few parts to look like adults. They reproduce by parthenogenesis (pronounced “virgin birth”), which means that Ms. Aphid doesn't need Mr. Aphid to manufacture Baby Aphid. They reproduce in that fashion all summer, sometimes cranking out a few winged females that fly to nearby plants to produce more wingless females. It is said that a female aphid who starts walking up the stem of a plant will be a great-grandmother by the time she reaches the top (notice the different sizes of aphids in these pictures and see if you can spot a birth in progress).
At some time in August through October (exactly when depends on the species of aphid), both male and female offspring are produced. These exchange bodily fluids, and the female lays the eggs that will overwinter and produce another generation of females in spring. The BugLady assumes that any piano-moving must wait until fall (a little Gertrude Stein joke, there).
The BugLady is searching for an adjective to refer to the slightly unsettling, dense, masses of soft-bodied aphids she sees on milkweed pods. Maybe “seething,” if “seething” can refer to insects that are pretty much standing still. Perhaps a BugFan come up with a good collective noun, like “an ooze of aphids?” “A crust of aphids?”
Bonus points for identifying the plant the red aphids are on.
Happy Trails to You,
This beautiful six-spotted fishing spider (Dolomedes triton) was photographed at Riveredge Nature Center’s vernal pond. Yes, the BugLady is aware that there are more than six spots visible, but the spot-count refers to spots on the underside of the abdomen. Fishing Spiders are Nursery web spiders (Family Pisauridae) of which there are about a dozen species north of the Rio Grande. They are often mistaken for wolf spiders. Members of the family use web to enclose their egg cases, but not to catch their prey. The female carries her egg case around and stays with it until the spiderlings have hatched and dispersed.
A spider of ponds and slow-moving streams east of the Great Plains, this gal (Mr. Fishing Spider is considerably smaller and has a slimmer abdomen) stalks around on the duckweed, algae, Riccia (an aquatic liverwort) and even the surface film of the water. Besides walking, they can run across the water or row across it using several pairs of legs. Sometimes they glide, pushed by the wind like a sailboat, or jump straight up off its surface to grab prey or to avoid becoming prey. Fishing spiders also dive and walk on plant stems underwater.
Like all spiders, they are carnivores, eating aquatic insects and, occasionally, tadpoles and tiny fish. They hunt on the surface film, eating insects that get stuck there and also eating their competition – the water striders. Fishing spiders wait on shore to detect the ripples of an insect struggling on the water; then they dart out, grab their prey with clawed front legs, bite it, and inject venom to kill it. They are, themselves, eaten by fish and frogs.
Fishing spiders have “book lungs,” alternating layers of air pockets and a blood-like substance. Their body is covered with short, water-repellant hairs that trap an additional layer of air against their body when the spiders submerge. With this “air tank,” they can stay under for as long as thirty minutes, but all that air may make them so buoyant that they have to grab a plant or rock to keep from floating to the surface.
Back in the early ‘70’s, the BugLady worked at the Schuylkill Valley Nature Center in Philadelphia. She lived on the third floor of a big old house – a metal fire escape, left over from the house’s mid-life stint as a sanatorium, provided her access through a modified kitchen window. The house had a widow’s walk above the attic so that the original owner’s wife could use a spyglass to see if her husband’s ship was in the harbor. The BugLady often sat up on the widow’s walk to commune at eye level with local Turkey Vultures and to visit the carpenter bees that excavated the railings of the widow’s walk (in retrospect, it’s a good thing the BugLady didn’t lean against the railings). Eastern carpenter bees (Xylocopa virginica) (xylocopus is from the Greek for “woodcutter”) would fly up and hover in the air, bobbing back and forth, staring at the intruder.
Yes, they do look like bumblebees, and at about 1” long, ECBs are the size of some of our larger bumblebee species. A carpenter bee’s rear is shiny and smooth (bumblebees have a hairy posterior), but its hind legs are densely hairy. Carpenter bees have big eyes, males more so than females (all the better to see you with, my dear), and compared to bumblebees, female ECBs have a large-headed look. Males sport a smooth, light/white patch on their face. Carpenter bees are strong, if noisy and clumsy, flyers. About a quarter of the ECBs the BugLady was photographing had a cinnamon-colored thorax.
ECBs are (now) classified in the family Apidae (some field guides place them in Anthophoridae), the same family as bumble, honey, and digger bees. There are about 500 species worldwide, but not all are plus-sized insects. ECBs are the most common carpenter bee species this side of the Mississippi, where they’re found in forests, grasslands, parks and gardens. There they fed on pollen and nectar from a wide variety of flat-ish flowers and as a result are considered valuable native pollinators in a world where pollinator populations are shrinking. Sometimes they cheat. Carpenter bees are medium-tongued bees (bumblebees have long tongues). If a flower is too deep and their tongue isn’t long enough they’ll do an end run, tunneling into the flower from the outside to harvest the nectar, by-passing the pollen and leaving a hole that other insects take advantage of.
Carpenter bees are famous for inventing particle board – a feat that doesn’t seem as awesome when the particles are from your redwood decks and railings. Their carpentry is tied to their reproductive behavior. In early summer, females make nests in seasoned wood like buildings, decks, and old, bark-free stumps. Carpenter bees are not social insects, though some species tolerate other nests close by (bumblebees typically nest in the ground and are social, with a queen maintaining a nest of workers throughout the warm months). Once a female stakes a claim on it, the wood will house carpenter bees all year.
A female ECB excavates a half-inch wide hole in wood. She prefers to use/extend the nest she hatched out in, so over the generations, the bees may leave wood decidedly honey-combed. One source says that she vibrates her body while rasping with her mandibles. When she’s about an inch into the wood, she makes a right turn and excavates with the grain for maybe six inches more, creating a gallery. It’s hard work - it takes almost a week to dig out an inch.
A single entrance leads to individual chambers, from six to twenty or so of them. When the chambers are prepared, Mom packs in an irregularly-shaped loaf of “bee-bread” made of the pollen and nectar she has collected. Pound for pound, carpenter bees lay some of the biggest eggs in insect-dom. She combines the sawdust from her efforts (you can locate holes by looking for small piles of sawdust) with saliva to make “particle board” partitions. This energy-intensive exercise has a price, the female dies soon after providing for the next generation.
When the egg hatches, the larva eats the bee bread and pupates within its chamber. It emerges as an adult in late summer, feeds for a while, and then retires to its natal nest for the winter. Males wake up first in spring, and the cycle restarts.
Big-eyed CBs like the ECB find their mates visually while flying and hovering and guarding flowers and nesting areas in hopes that a female will appear (smaller species of CBs use pheromones). The ECB on the widow’s walk was undoubtedly a curious male. Males are harmless - no stinger - and you have to work pretty hard to get stung by the non-aggressive females, but they will oblige eventually. There are reports of males making romantic overtures to other insects and even small birds, and males will try to escort interlopers out of their space. If you find their scrutiny unsettling, males can apparently be distracted by tossing a small object past them.
ECBs are a hot topic at Exterminators’ websites. Some non-exterminator sources insist that the damage is minor and is primarily superficial – close to the surface of your porch rails or siding (others concede damage, but say that it may take decades for that damage to become serious). Larger and more upsetting excavations may be made by woodpeckers, Mother Nature’s Exterminators, looking for a meal. There are mechanical and chemical controls for ECBs, and you can also “redirect” them by putting out some wood especially for them.
For some nifty shots of ECBs hovering: http://bugguide.net/node/view/284272/bgimage and working with wood: http://bugguide.net/node/view/174189/bgimage, try these bugguide.net links.
You can prevent carpenter bees from boring into structures by painting with oil-based paints. Carpenter bees avoid oil-based paints as well as wood covered in bark. Most carpenter bees will avoid hard wood as well, so choose oak over pine when building.
Check for holes every spring, when the carpenter bee mates. The female builds her nest to lay her eggs. The entrance will be a perfectly round hole, a little less than a half-inch in diameter. There will be a sprinkling of sawdust outside the hole, and excrement may be visible on the wall around it.
You should be able to vacuum out the female and caulk over the hole before a nest is built. You can caulk her into the nest, but she will die in there rather then boring her way back out. Be careful, she is the only one in the nest that could sting you. Put several coats of an oil-based stain or paint over the area to deter the bees from returning.
Supply your bees with a structure of soft wood with a straight grain for easiest access. Leave it untreated and even go so far as to drill a small half-inch hole in it. This will encourage your carpenter bees to nest here. Carpenter bees will stay with a nest, generation after generation, rather than seeking out and building a new nest. According to Ohio State University entomology department, the female bores in for 2 inches, turns and bores another 6 inches, so make sure your structure allows this much space.
The western carpenter bee likes oak, redwood and eucalyptus. The eastern carpenter bee prefers pine, cypress, redwood, fir and cedar. Keep this in mind when you are trying to redirect your carpenter bees.