Friday, October 30, 2009

Halloween Special: Ghosts and Pirates

What is more appropriate for Halloween than ghosts and pirates? We are not talking about trick-or-treat costumes, though, but spiders. Come to think of it, what is more appropriate for Halloween than spiders?! Just last week I found both kinds on an unseasonably warm night (October 21) here in South Deerfield, Massachusetts.

Both ghost spiders (family Anyphaenidae) and pirate spiders (family Mimetidae) prowl in search of prey. The similarity ends there, though, as they don’t resemble each other in the least, and their lifestyles are very different.

Ghost spiders are, not surprisingly, pale in color for the most part, and generally nocturnal in their habits, haunting foliage in pursuit of insects to eat. By day they hide in curled leaves that they tie together with silk.

Despite their name, ghost spiders are not very intimidating to humans. Adults reach a maximum of only a bit more than 8 millimeters. This one, a specimen of Hibana gracilis, was probably about six millimeters in body length. Big enough to take down the midge it is munching on, though. I think spiders recognize on some level the attractiveness of outdoor lighting to insects, as that is the situation I found this one in, and the pirate spider as well.

Pirate spiders are easily identified by their four eye patches and two wooden legs. But seriously, folks, the long spines on their legs help differentiate them from the cobweb spiders and sheet-web weavers that they otherwise might be mistaken for. The resemblance to other spiders is further complicated by the fact that you sometimes find pirate spiders in the snares of cobweb weavers. Their appearance there is as sinister as their name suggests.

Pirate spiders eat cobweb spiders, as well as orb weavers and other spiders. They dispatch the rightful owner of the web by biting the other spider on its legs, feeding from one after the other until the victim is totally drained. One reason for attacking the legs of its prey might be that the jaws of pirate spiders are fused at their base, not permitting the spider to open its mouthparts wide enough to bite other parts of its victims.

The specimen I found last week was Mimetus puritanus, the most common species in the eastern United States. There is a total of fourteen species in the genus in North America, however, and another ten that remain undescribed (awaiting the assignment of names by arachnologists).

BOO! Just making sure you are still paying attention. Ar-r-r-r-g, matey! Be on the lookout for ghosts and pirates in your own neighborhood.

Tuesday, October 27, 2009

I See Dead Spiders

I have been almost literally wading through vials of dead spiders in my lab at the University of Massachusetts (Amherst) the last few weeks. My supervisors had tried to come to terms with a real arachnologist in Canada to identify the pitfall trap specimens from last year’s samples, but apparently international relations were too complicated and it fell to me to try and make heads and tails (cephalothoraxes and spinnerets?) of the many members of the order Araneae that were trapped last summer.

The chemicals and processes used in collecting, cleaning, and preserving the specimens often leaves them in less than optimal condition for identifying them later on, and the biggest challenge I’ve had has been finding intact specimens, or at least assembling all the parts scattered throughout a given vial. Legless specimens abound, as do those without abdomens.

Another problem one encounters is finding mature adult specimens. Many specimens can be determined to the family level of classification as immatures, or even spiderlings, but genera and species can be impossible to conclude without having the external genitalia to examine. The majority of specimens I find to be juveniles or “penultimate adults,” the term for spiders one molt removed from adulthood. Arg!

Still, I am learning a great deal about spider anatomy and am able to execute identifications to a respectable degree despite the obstacles. I have at my disposal several fine literature references as well as excellent online resources. Ultimately, I must rely on patiently putting the specimens through “keys,” documents in the form of couplets that direct you to other couplets and eventually take you to the name of a genus or species. When it works, it is a joyous occasion. More often than I’d like, though, the result is one of sheer frustration.

The diversity of the spider fauna that I’m finding is truly amazing. Among the more dominant families are the Linyphiidae, which includes the tiny “dwarf spiders,” subfamily Erigoninae. There seems to be no end to the number of different species, and some of them sport bizarre formations on the cephalothorax . Males of Oedothorax trilobatus sport tumor-like swellings that give the species its name. Meanwhile, some males of Walckenaeria communis can have a horn-like extension of the cephalothorax. The spiders themselves measure only about two millimeters in total body length.

At the other end of the spectrum are relative monsters like Wadotes hybridus, a member of the hacklemesh weaver family Amaurobiidae that can reach 14 millimeters at maturity. These are powerful, brutish arachnids with heavy legs and enormous chelicerae (jaws).

You can see some of the other strange and wonderful species I’m identifying and imaging by following my string of images at Bugguide.net, which start with the most recent uploads. Live vicariously in arachnid land.

Sunday, October 25, 2009

The End of Extension in Michigan?

My good friend Bug Girl just posted a very disturbing entry to her own blog. Apparently the Michigan legislature intends to abandon the state’s Cooperative Extension Service.

This is just simply embarrassing, akin to the legislation in Kansas concerning evolution and creationism. Is that the kind of reputation that Michigan wants? Of course not. Extension agents help people across the entire globe because they are literally and figuratively plugged into networks of other professionals, trading ideas and helping each other in myriad ways. No state can afford to essentially operate in a social, economic, or scientific vacuum, but that is what is going to happen if the legislators don't see the error of their ways.

It is my humble opinion that there are no more important people than extension service personnel because they serve as the public face of science, educating the masses in a variety of formal and informal ways. They also serve as mentors to young students of science and agriculture via 4-H and other programs.

I urge you to lend your voice of support to the comments calling for an end to this budget-cutting nonsense over at Bug Girl’s Blog. Together, we can stop this and help ourselves as well as Michigan residents who would be so terribly hurt by an end to the Cooperative Extension Service. Thank you.

Tuesday, October 20, 2009

Spider Season


Fall is also spider season, at least in temperate climates. I am asked about spiders much more often in autumn than at any other time of the year. Why is this so? What does it mean?

Orb-weaving spiders in particular are much more conspicuous later in the year than in the spring and summer. This is true for several reasons. The spiders are mature, and therefore larger, for one thing. Females are also competing for the best “web sites” to optimize their prey-catching opportunities. This means that some end up spinning in less-than-ideal spots, like across your door. They could conceivably be there by choice, though. Spiders are quick to learn that outdoor lighting attracts lots of insects, so your front porch might be great real estate for the arachnids.

Indeed, a few species seem to actually prefer human constructions. The “barn spider,” Araneus cavaticus, is seldom found anywhere else. The females are quite large by North American spider standards, and can be rather intimidating when they stretch their snares across the rafters and under the eaves. Ironically, the webs are rather small compared to the spiders themselves.

Females of many orb weavers spin their webs at night, remaining concealed in “retreats” in curled leaves and other shelters by day. They connect a “signal thread” to the hub of their circular snare to literally keep them in touch with the web, alerting them to the impacts of any insect victims that might become entangled during the day.

Other orb weavers sit in the hub (center) of their webs at all times, like the “cross spider,” Araneus diadematus, pictured at the top of this entry. When disturbed, the spider may shake violently in its web, perhaps startling the potential predator into abandoning its intended attack.

While female spiders are stay-at-homes, male spiders wander in search of mates, even those species normally confined to webs. Autumn is the season in which many of these nomadic suitors find there way indoors by mistake, freaking out female humans in the process. The male spouse is then recruited to dispatch the male spider. I encourage folks to consider simply ushering the spider into a container and taking it back outdoors where it can resume its romantic pursuits in a more appropriate habitat.

Mature male spiders can often be identified by their more slender bodies, longer legs, and modified “palps” or “pedipalps,” leg-like mouthparts that often resemble miniature boxing gloves.

Some spiders simply hunt on foot and don’t bother with a web. One of the more common examples of this kind of hunting spider are members of the genus Trachelas in the family Corinnidae. They are often encountered indoors at this time of year. Once considered mildly venomous to humans, they are now classified as harmless.

Wherever you find spiders, enjoy them in their roles as master weavers and pest control patrol. You can safely relocate indoor spiders with the “cup and card” trick. Simply place a cup, glass, or other container over the spider, slip an index card under both the spider and the mouth of the container, turn them over, and take them outside. The spider and your spouse will thank you for it.

Saturday, October 10, 2009

Indoor Insects of Autumn (part 4 of 4)

This is the final installment of a four-part series addressing insects frequently seen indoors at this time of year when they seek shelter for hibernation during the colder months. This entry will introduce the “multicolored Asian lady beetle,” Harmonia axyridis.

Like the brown marmorated stink bug, the multicolored Asian lady beetle, also known as the “Halloween lady beetle” for its abundance at the end of October, is not native to North America. It was repeatedly introduced here by state, federal, and private interests to augment native lady beetles for control of aphid pests in orchards. As early as 1916 an effort was made to establish this species in California. Subsequent efforts there and elsewhere appeared to fail each time.

Finally, in 1988, viable populations were discovered near New Orleans. Whether this was the result of a planned introduction, or an accidental importation, it marked the start of something big. Today, Harmonia axyridis is found over most of the United States and adjacent southern Canada, save for the southwest U.S.

This species is not easily identifiable because it is so variable in color and pattern. Most individuals have bright red elytra (wing covers) with eighteen or nineeen black spots, but they may be orange and spotless, or even black with only a pair of red spots. There is every combination in between, too. They can thus be confused with many native species.

The overriding clue to their identification seems to be their sheer abundance. There is some circumstantial evidence that they might even be displacing native species, but probably not as much so as another non-native lady beetle, the seven-spotted (“C-7”) lady beetle, Coccinella septempunctata.

Nowhere is the abundance of Harmonia axyridis more obvious or obnoxious than when they congregate indoors while seeking snug spots in which to overwinter. Their sudden appearance usually means a flood of telephone calls from irate homeowners to the state department of agriculture and county extension agents. It is no one agency’s “fault,” though, and at most the beetles are a “nuisance pest” that can sometimes emit a foul odor or stain fabrics. They most definitely do not breed indoors or eat clothing or blankets. In fact, they subsist on fat reserves during the colder months, not feeding at all.

There are persistent reports of the insects biting people, but this does not represent an attack as much as curiosity. Insects in general investigate things through taste, smell, and touch. Nor does it mean the beetle is acting in self-defense. Lady beetles defend themselves by secreting a noxious yellow fluid from their “knee” joints in a behavior known as reflex bleeding. This liquid smells awful and can leave a stain.

Preventing multicolored Asian lady beetles from entering your home or office building is the easiest way to avoid problems. Replace worn weatherstripping on doors. Repair holes in widow screens, and seal other cracks and crevices. Consider vacuuming up any beetles that do make it indoors and releasing them outdoors near a woodpile or other sheltered situation away from your home.

You might also consider painting your home a different color. Evidence shows that the beetles are most attracted to pale hues such as white, gray, and yellow.

More information about these beetles can be found online through fact sheets from Ohio State University and the USDA Agricultural Research Service.

The Art of Insect Tracking

Last Saturday night, October 3, I joined friends from Athol, Massachusetts to travel to the town of Cummington for the opening reception of an art exhibit by Charley Eiseman and Noah Charney. The two friends collaborate to teach tracking workshops and other field courses, but have also worked to produce the forthcoming book Tracks and Sign of Insects and Other Invertebrates, published by Stackpole Books with an expected release date of March, 2010. The exhibit, which runs through the end of October at the Cummington Community House, 33 Main Street, features stunning images taken for the book.

Noach Charney has become so enthralled with the intricate designs produced by insects in the course of their life cycles that he intends to produce his own coffee table book that celebrates these signs and patterns as literal art. Noah has a real eye for this and is painstaking in his commitment to producing high quality images. He is not above fooling his audience, either, posing optical illusions while rendering portraits of what insects leave behind. This image of leafcutter bee “damage” is perhaps the representative picture for the entire project. Can you tell what is going on here (hint: this is not a studio shot, and only minor manipulation of the leaves was involved)?

Charley Eiseman (right) met Noah (left) years ago when they helped found the “Woodsy Club,” as Charley’s mom affectionately calls it. Together with other like-minded souls, they practiced tracking, outdoor survival skills, and other activities. The two might call themselves “slackers” and poke fun at each other’s shortcomings, but there is nothing about them that is unprofessional when it comes to scientific endeavors. Keen eyes and endless curiosity have helped them spot the most cryptic of arthropod-created objects and solve enduring mysteries of “what did that?”

Anyone who hangs out with Noah and Charley will learn what true friendship means, and will laugh a lot along the way. You can’t help but come away with an appreciation of all things insect- and spider-created, or learn the art of observation and patience, either.

This blog entry is not just to promote their book and photography skills. You have to read the wonderful story in the Boston Globe for that. I just like these guys and the fine qualities they exemplify. Do take in the exhibit if you find yourself in the vicinity of Cummington, and by all means visit their website, the Northern Naturalists to keep track of their latest activities (no pun intended).

Tuesday, October 6, 2009

Indoor Insects of Autumn (part 3 of 4)

This is the third installment of a four-part series addressing insects frequently seen indoors at this time of year when they seek shelter for hibernation during the colder months. This entry will introduce the “brown marmorated stink bug,” Halyomorpha halys. Special thanks to John R. Maxwell for sharing his images.

Unlike the western conifer seed bug and the boxelder bugs, the brown marmorated stink bug is not native to the North American continent. It was first detected in Allentown, Pennsylvania in September, 1998 but probably arrived at least two years earlier. The insect hails from Asia, being indigenous to China, Japan, Taiwan and Korea.

Thus far, H. halys has amounted to a mere “nuisance pest” that appears in numbers on the exterior of homes as it seeks shelter for the winter. The adult insects fly well, and sometimes manage to creep indoors, much to the consternation of property owners. The fact that they can deploy their scent glands when under duress makes them even more unappealing.

Outdoors, during the spring and summer months, nymphs and adults feed on a variety of plants, shrubs, trees, and fruits. They sip liquid sap and fruit juices through beak-like mouthparts collectively called a rostrum. Their feeding causes mostly cosmetic damage and they have not yet attained pest status for that reason. This is not the case in their native range where they are especially problematic for soybean growers.

Unfortunately, these are non-descript bugs that are easily confused with innocuous native stink bugs like those in the genus Brochymena. Older nymphs like this one do sport distinctive spikes and spines, and black and white-banded legs. It is the aggregation behavior of the adults in the fall that seems to be their most unique and identifying characteristic.

Since its first appearance in Pennsylvania, the brown marmorated stink bug has been discovered in the following states: Connecticut, Delaware, Idaho, Indiana, Illinois, Iowa, Maine, Maryland, Minnesota, Mississippi, Montana, New Jersey, New York, Nevada, Ohio, Oregon, South Dakota, Tennessee, Utah, Virginia, Washington, West Virginia, Wisconsin, Wyoming, and the District of Columbia. Specimens have also been intercepted by agriculture officials in California and Florida. Should you suspect you have found this species in a state not on this list, you are urged to report your finding (backed up with specimens whenever possible) to your state department of agriculture.

As with all of the insects being profiled in this series, care should be taken to exclude the bugs from entry into structures by repairing worn weatherstripping, mending holes in window screens, and sealing other possible points of entry with silicone caulking and other such materials.