Thursday, November 20, 2014

Lakin Grasshopper

Grasshopper species diversity in the southwest U.S. presents enough of a challenge for the amateur naturalist, but then you have the Lakin Grasshopper, Melanoplus lakinus, that can apparently pass for several hundred species all by itself. That's an exaggeration, of course, but there is such great variability in the color, pattern, and wing length of this species that it is mind-boggling.

Lakin Grasshopper male

Lakin Grasshopper is often overwhelmingly abundant in disturbed habitats such as vacant lots and weedy fields and rangeland filled with its favorite host plants, members of the goosefoot family Chenopodiaceae. This includes Russianthistle ("tumbleweed"), kochia, and native saltbush (Atriplex spp.). It will also feed on various forbs and grasses such as lambsquarters, western wheatgrass, and downy brome. Despite high population densities in some years, it is seldom a crop pest.

Lakin Grasshopper female

This is a grasshopper of the Rockies and Great Plains, ranging from South Dakota and southern Minnesota south through western Iowa, most of Kansas, western Oklahoma, the west half of Texas, plus Nebraska, Colorado, New Mexico, and the eastern two-thirds of Wyoming, Utah, and Arizona. It also occurs deep into central Mexico.

Red form female from New Mexico

Melanoplus lakinus is a pretty "average" grasshopper. Adult males measure about 22 millimeters in body length, females 30 millimeters. Most specimens are short-winged as adults, but some are fully-winged. The overall color varies greatly from brownish or gray to green or even red. The tibia ("shin") segment of the hind leg is usually blue, armed with spines that are black or at least black-tipped. The inner surface of the hind femur ("thigh") is often reddish in part, especially along the bottom edge where the tibia folds into it. The top surface of the femur is most often marked with pronounced dark bands.

Green form female from Colorado

Dark bands on the abdomen, especially near the base, are helpful in recognizing the species in the field, but ultimately one has to examine the external genitalia of the male to confirm identification.

Ok, so how do you even tell apart the different genders? Below is an image that shows the male and female side-by-side, from the rear. The male is on the right. The female is on the left, but her abdomen is twisted to repel his advances, or accept his overtures, I'm honestly not sure which because I did not stick around long enough to see the outcome.

Male on right, female on left, rear view

The male's parts are pretty complicated, but you want to look at the shape of each "cercus," paired tail-like appendages. In the example below, we see that the cercus of M. lakinus is shaped something like a Hershey's candy kiss: broad at the base and tapered toward the tip. Next, take a look at the shape of the subgenital plate. It is best to view it directly from the rear, like in the image above. We can see it has a low, blunt tooth right in the middle. The supra-anal plate also offers species-specific details, but they are more difficult to discern, especially in images.

Anatomy of male M. lakinus

When two grasshoppers do get together, it looks like this:

Mating pair, male on top

Pretty kinky, almost literally! Mated females deposit clusters of eggs ("pods") in the soil by telescoping their abdomen as deep as it can reach. The eggs are held together by a kind of foamy secretion that hardens to protect the mass from environmental extremes. The eggs hatch in late May or early June, on average, the following year. In Arizona, where summer monsoons trigger hatching, emergence is usually in early July. The nymphs pass through five instars (an instar is the interval between molts), reaching adulthood in about a month.

Long-winged female from New Mexico

This year was a good one for the Lakin Grasshopper here in Colorado, and also in New Mexico, as heavy spring rains provided the nymphs with plenty of food after years of draught. The adults have hung around a long time, too. Just yesterday I spotted one basking on the sunny side of a building in our townhouse complex.

Sources: Capinera, John L. , Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca, NY: Comstock Publishing Associates (Cornell University Press). 249 pp.
Branson, David H. and Bethany Redlin (eds.). 2004. Grasshoppers: Their Biology, Identification and Management. 2nd Edition. US Department of Agriculture, Agricultural Research Service.
Grasshoppers of Colorado

Sunday, November 16, 2014

Ballooning Spiders

Do you remember that meme that went around on Facebook expressing gratitude that spiders can't fly? Here it is:

Well, not so fast my friends. Spiders actually can get aloft, thanks to the phenomenon of "ballooning."

Ballooning is the number one way that spiders disperse themselves across the landscape. It is practiced mostly by immature spiders that do not weigh much and are easily blown away; but many spiders are quite small as adults, too, and they can balloon as well. It is a way spiders avoid competition with each other for prey and "web sites."

This technique is brilliantly simple. The spider simply climbs to the top of a vertical object like a plant stalk, fencepost, or mailbox, and issues threads of silk from its spinnerets. When the spider detects a breeze, it stands on "tiptoe," facing the wind, and tilts its abdomen toward the sky. With any luck, the air currents whisk the spider off its perch and up, up, and away it goes.

Ballooning wolf spider, Blue Stem Prairie Open Space

Recent investigations also suggest that spiders can harness electrostatic forces in the atmosphere to balloon on calm days and/or achieve greater success than they might from the wind alone. This is beyond both my grasp of physics and the scope of this post, but you are welcome to read more here.

The spider families that utilize ballooning the most include the crab spiders (Thomisidae), orbweavers (Araneidae), long-jawed orbweavers (Tetragnathidae), and dwarf spiders (subfamily Erigoninae of the Linyphiidae). Personally, I have also seen wolf spiders (Lycosidae) ballooning, like this one at Bluestem Prairie Open Space along the edge of Johnson Reservoir near Colorado Springs, on March 10, 2014.

Alex Harman also documented a ballooning event of immature Six-spotted Fishing Spiders, Dolomedes triton, at Horicon Marsh in Wisconsin on October 26 of this year.

© Alex Harman

Ballooning is most often performed in spring and late fall by spiderlings, but adult dwarf spiders balloon during the winter, too. The most favorable conditions for a "launch" are when the weather changes to warm days after a prolonged period of cold. This creates updrafts as the ground temperature heats rapidly. Here on the Front Range of Colorado, gusts can be strong and spiders are no doubt carried a long distance.

Darwin, during his voyage on the H.M.S. Beagle, noted large numbers of ballooning spiders coming to rest on the ship's rigging. At the time, the vessel was approximately 100 kilometers off the eastern coast of South America, and Darwin suspected the spiders had drifted at least that distance, if not farther.

Not only are ballooning spiders transported horizontally, they can be blown to high altitudes as well. At least one spider has been collected by airplane at 15,000 feet over Tallulah, Louisiana during a study that lasted from 1926-1931 (Glick, 1939). The greatest number of specimens was still taken at well under 1,000 feet, however.

Gossamer, © Fairyist.com

"Gossamer" is the term for the silk lines spiders create when ballooning, and the cumulative effect can literally shroud the landscape in a blanket of gossamer as the spiders come to rest. Considering that there are easily dozens upon dozens of spiderlings per egg sac, multiplied by dozens of egg sacs, multiplied yet again by however many species exist in a given area, it is no wonder that ballooning individuals can create such a spectacle of spent silk.

Not every attempt at aerial navigation is a success, of course. I personally witnessed a small crab spider take off from a utility box in my neighborhood, only to land unceremoniously about three feet away in the street.

Ballooning crab spider, Xysticus sp., Colorado Springs

Still, spiders are able to achieve amazing feats this way. They are often among the first animals to colonize islands, and habitats destroyed by storms, volcanoes, and other natural disasters. Re-colonization of the island of Krakatau, and the blast zone around Mount St. Helens, are two of many well-documented instances of ballooning spiders conquering new territories.

Sources: Brunetta, Leslie, and Catherine L. Craig. 2010. Spider Silk. New Haven, Connecticut: Yale University Press. 229 pp.
Foelix, Rainer. 2011. Biology of Spiders (Third Ed.). Oxford: Oxford University Press. 419 pp.
Glick, P.A. 1939. The Distribution of Insects, Spiders, and Mites in the Air. Washington, DC: United States Department of Agriculture Technical Bulletin No. 673. 151 pp.

Friday, November 14, 2014

Thank you, followers!

I can think of no better way to use my 500th post than to thank the many people who read this blog faithfully. Without followers like you, I never would have reached this milestone. Many days I have wondered why I bother posting, but then I look at the growing number of icons under "members" in the right sidebar, and remember who is waiting for the next story.

We ♡ our followers!

Friends who are more tech-savvy than myself also remind me that there are hundreds of other people looking in that don't show as members. Every month or so I also get a report from Google that surprises me with how many "hits" this page receives daily, and where those hits are coming from. Sure, most of my audience is from the U.S. and Canada, but I also have visitors from the United Kingdom, Australia, and South Africa. I may need to make some field trips abroad so I can talk about arthropods from those places, too.

Last month I had over 9,000 new visitors, 274 returning visitors. Facebook and Blogger are my top "social sources" by far, with WordPress, reddit, and Twitter bringing up the rear. That surprises me because I get re-tweeted all the time (and thank you for that!).

My overall goal is to reach an audience unfamiliar with insects and arachnids, providing the most accurate and relevant information I can. I also want to encourage other naturalists to keep on finding and observing invertebrates, reporting their own sightings, images, videos, and audio recordings to appropriate archives. I welcome suggestions for how to improve on that.

It is important to note that many of my posts could not be possible without input from entomologists and arachnologists far more expert than myself. I frequently need to have specimens identified before I can write about the species, genus, or family, and were it not for specialists willing to share their knowledge, I would be nowhere.

Lastly, if you have an enterprise that has anything to do with a positive approach to natural history, have written a book, or do public programs, I would be willing to put up an advertisement for you, as I have done with BioQuip. Don't be shy, I am always delighted to reward good work, and would happily devote a blog post to your business, achievements, or observations, especially if you do not have a blog of your own.

Thank you again for making "Bug Eric" a successful venture. I look forward to continuing to produce it for as long as I can. There is certainly no shortage of subject matter, even if I had started several lifetimes ago. Oh, wait, the internet has not even existed for that long.

Tuesday, November 11, 2014

Little Bugs with a Big Bite: Minute Pirate Bugs

Sometimes it seems the tiniest of insects is the biggest nuisance. Mosquitoes come to mind, as well as black flies, and "no-see-ums" or "punkies" (biting midges in the family Ceratopogonidae). One other insect often responsible for surprisingly painful bites is the aptly-named "minute pirate bug." There are about 90 species in the family Anthocoridae found in North America, in 22 genera, but only a few cause us grief.

Insidious Flower Bug biting me in Colorado

The Insidious Flower Bug, Orius insidiosus is, appropriately, the species most likely to get under your skin. Well, on your arm, hand, or neck, where it will likely probe you painfully. At only 2-2.5 millimeters, it is possible to overlook it entirely when trying to pinpoint the source of your irritation. In the right light, however, the little bug appears bright white and black.

Despite dispensing unprovoked bites, Orius insidiosus is actually a highly beneficial bug. It is a predator of many crop pests like very young caterpillars of the corn earworm, plus insect eggs, aphids, whiteflies, thrips, and mites. Consequently, this minute pirate bug is reared commercially and sold to farmers as a biocontrol agent.

It takes only twenty days, on average, for O. insidiosus to go from egg to adult. Females lay two eggs per day, and about thirty during their lifetime. Each ovum is deposited in foliage such that the top of the capsule protrudes above the leaf surface. In about four or five days, the first instar nymph emerges from the egg. During the next two or three weeks, the nymph goes through a total of four more instars before transforming into a fully-winged adult bug. The adults live an additional three or four weeks.

Insidious Flower Bug biting me in Kansas

Adult Insidious Flower Bugs overwinter in leaf litter and probably other debris on the ground. Several generations can be produced annually over the insect's wide geographic range. It occurs east of the Rocky Mountains, plus parts of California, and has been introduced to British Columbia. Because it is available commercially, it has likely spread elsewhere, too.

Adult Anthocoris musculus, Colorado

Another species I have found commonly here in Colorado Springs is Anthocoris musculus. It is a real giant by pirate bug standards, measuring 3.4-4.0 millimeters as an adult. I have found it associated with cottonwood trees, and it is well-known from willows and other deciduous trees and shrubs as well as herbaceous plants.

Nymph of Anthocoris musculus, Colorado

It is potentially an important predator in orchards, and has been observed eating red mites and "eye spotted bud moth" in Nova Scotia (Kelton, 1978). This species ranges throughout most of North America including Alaska and northern Canada.

The next time the pirate bug bites, simply utter "Ar-r-r-r!" and remember their beneficial qualities. After all, they are probably keeping your garden free of other tiny pests.

Adult A. musculus feeding on unknown object, Colorado

Sources: "Minute Pirate Bug aka. Orious insidiosus," Evergreen Growers Supply.
Gibb, Tim. 2006. "Have a thick skin when it comes to Insidious Flower Bugs," Purdue Plant & Pest Diagnostic Laboratory, Purdue University Extension
Hull, L.A. and R.L. Horsburgh. "Minute Pirate Bug, Orius insidiosus (Say)," Mid-Atlantic Orchard Monitoring Guide.
Kelton, Leonard K. 1978. The Anthocoridae of Canada and Alaska. Ottawa: Canada Department of Agriculture. Publication 1639. 106 pp. (PDF).
Slater, J.A. and R.M. Baranowski. 1978. How to Know the True Bugs. Dubuque, Iowa: Wm. C. Brown Company Publishers. 256 pp.