Thursday, October 8, 2015

Tree Cricket Courtship

Tree crickets, genus Oecanthus, are having quite the year here along the Colorado Front Range. Last month I went to Garden of the Gods park in Colorado Springs and could hardly go twenty feet without hearing a male tree cricket singing in the tall weeds or from a yucca blade. I even managed to capture videos of their singing and courtship.

Male Snowy Tree Cricket singing

There are five species of tree crickets in Colorado: the Prairie Tree Cricket, Oecanthus argentinus, Western Tree Cricket, O. californicus, Snowy Tree Cricket, O. fultoni, Black-horned Tree Cricket, O. nigricornis, and the Four-spotted Tree Cricket, O. quadripunctatus. Determining the species of a given individual is difficult to say the least because identification frequently hinges on the markings present (or absent) on the first two segments at the base of the antenna. I know! The whole insect is only about twenty millimeters maximum.

It is much easier to tell which gender is which. Females are very slender, with the front pair of wings hugging the body tightly. The short, stout ovipositor, used to insert eggs into berry canes and other plant stems, is easily visible.

Female tree cricket

Males on the other hand have the front wings greatly expanded into paddle-shaped musical instruments that make them look more like green lacewings than crickets. The intricate pattern of veins is all about lending support to the membrane that generates, amplifies, and projects the male's song. He lifts his wings into a heart shape at a 90-degree angle to his body in order to sing.

Snowy Tree Cricket singing

The song is produced when a "scraper" on one wing is drawn across a "file" on the other wing, near where the wings join the thorax. The rapidity with which this happens cannot be captured by ordinary video cameras. Some male tree crickets align their wings with gaps in foliage, or even chew holes in leaves, to reduce acoustic interference and further intensify their call.

Singing male tree cricket with exposed metanotal gland in center of thorax

Like most crickets and other members of the order Orthoptera (grasshoppers, katydids, crickets), males have more than one kind of song. Once a male successfully lures a female, he switches to a softer song to help her orient to him. His raised front wings also expose a metanotal gland in the center of his thorax, which secretes a substance that the female feeds on. This is something of a distraction so that he can transfer a spermatophore, or "sperm packet" to her genital opening. The packet appears as a small, pearly blob near the tip of her abdomen in the video and images below.

Female tree cricket feeding from male's metanotal gland

The spermatophore takes time to drain sperm into her oviduct, and the female would undoubtedly eat it if she did not have the more attractive metanotal secretion to lick instead. She is sufficiently addicted that she feeds for several minutes after mating.

Tree crickets are omnivores, feeding on plants and small insects like aphids. Some species are truly arboreal, living in shrubs or high in trees, but a surprising diversity can be found in grassy fields, meadows, and similar habitats.

Male Snowy Tree Cricket at rest

There are many wonderful online resources to help you appreciate and identify tree crickets. One of the best is Singing Insects of North America, which covers grasshoppers, katydids, and cicadas along with crickets. was created by Nancy Collins, a citizen scientist who has become a leading authority on tree crickets, even discovering a species new to science. Lisa Rainsong writes and illustrates the blog "Listening in Nature," which covers all kinds of acoustic phenomenon in the outdoors.

Male Prairie(?) Tree Cricket singing

Enjoy listening to, and looking for, tree crickets in your own neighborhood. Finding them is a challenge, but your patience will be rewarded. Above all, have fun.

Sources: Collins, Nancy. 2014. All About Tree Crickets. Parker, Colorado: Outskirts Press. 48 pp.
Dethier, Vincent G. 1992. Crickets and Katydids, Concerts and Solos. Cambridge, Massachusetts: Harvard University Press. 140 pp.
Elliott, Lang and Wil Hershberger. 2007. The Songs of Insects. Boston: Houghton Mifflin Company. 228 pp.

Thursday, October 1, 2015

The Grasshopper Hunt

The Aiken Audubon Society here in Colorado Springs asked me to speak at their September monthly meeting, and to lead a field trip beforehand. I chose the topic of grasshoppers since there is so much diversity here. The field trip was to Homestead Ranch Regional Park near Peyton, Colorado (El Paso County). I was surprised and delighted by the turnout, and the interesting animals we encountered.

Carolina Grasshopper basking

We were fortunate to have two young men, Seth and Zach Vogel, and their father, Tim, along for the trip. The boys helped find many more animals than we would have were we left to my own devices. They have a keen eye, endless stamina, and great enthusiasm. Tim employed a GoPro® camera to record parts of the expedition in this video.

© Tim Vogel

The Mile High Bug Club was represented by Bell Mead and myself; and Aiken Audubon by Jeannie Mitchell, Leslie Holzmann, and Bill Maynard. Alison Kondler even came down from the Denver area. Thankfully, the weather was sunny, but not too hot.

Plains Lubber grasshopper

We had not even made it beyond the playground and picnic shelter before we saw Carolina Grasshoppers basking on the pavement, and the boys had found an enormous Plains Lubber Grasshopper, Brachystola magna. The latter brought out the "'hopper-razzi," cameras clicking away.

Plains Lubber grasshopper draws a crowd

Further along the trail through grassy habitat on a gentle slope, we encountered several species of spur-throated grasshoppers in the genus Melanoplus, plus Pallid-winged Grasshoppers (Trimerotropis pallidipennis), and the Northwestern Red-winged Grasshopper, Arphia pseudonietana.

While I was explaining how to identify a particular species, the boys brought over a really nice find: a male Mormon "Cricket." The Mormon Cricket, Anabrus simplex, is not a true cricket, nor a grasshopper, but a kind of shield-backed katydid.

Mormon "Cricket" male

Seth and Zach located these large insects by homing in on their "song," a kind of buzzing sound produced by the males rapidly rubbing their short wings together.

We entered a narrow zone of pine trees near the summit of the slope we were traversing, and that brought us another species of grasshopper, apparently confined to that wooded habitat. The Kiowa Grasshopper, Trachyrhachys kiowa, is another of the "band-winged grasshoppers" named for the dark band on the colored hind wing. The hind wings are only visible when the insect flies, and most grasshoppers fly only short distances before landing and once again becoming nearly invisible owing to their superb camouflage.

Kiowa Grasshopper with hind wing spread

Band-winged grasshoppers can make noise in flight. This is called "crepitation," and is a rattling or crackling sound, presumably as front and hind wing rub together....but the sound can be produced at will, so it is something of a mystery how it is produced.

The hill terminates in a rolling plateau, and the grassland changes a bit in composition. Here we heard slant-faced grasshoppers, hidden from view. Slant-faced grasshoppers cling to vegetation in the vertical plane rather than crawling on the ground like band-winged grasshoppers usually do. They produce sound not by crepitation but by "stridulation." The male grasshopper rubs the inside surface of his hind femur ("thigh") against veins of the folded front wing. The result is a "zip-zip-zip" kind of song.

We ended our hike at a circular water trough for horses and cattle, fed by a well with a windmill pump. The water looked awful, but was full of life. It took no time at all for Zach to spy a Barred Tiger Salamander (Ambystoma mavortium), one of at least two inhabiting the pool.

Barred Tiger Salamander

There were also water striders (insect family Gerridae), backswimmers (Notonectidae), diving beetles (Dytiscidae), and a Giant Water Scavenger Beetle, Hydrophilus triangularis (family Hydrophilidae). Various dragonflies circled as well.

Giant Water Scavenger Beetle

Everyone appeared delighted by the whole adventure, and I am very happy to see what is apparently a growing demand for field outings geared to organisms other than birds, or at least in addition to birds. I would very much like to do more of this kind of thing, all over the U.S., so keep those invitations coming!

Sunday, September 27, 2015

The Tarantula Hunt

Heidi and I had the pleasure of going on a hunt for tarantulas on Labor Day, September 7, with Megan Miller, Jordan Spalding, and Bell Mead. Thanks to Ryan Nefcy, we learned of a location in Pueblo County, Colorado where one can reliably find tarantulas, genus Aphonopelma. Not only did we have success, but we found some other spiders, too, as well as some spectacular grasshoppers.

There are at least four species of tarantulas found in Colorado, and although we suspect the ones at the Pueblo County location are Aphonopelma hentzi, we would need to perform invasive procedures on a spider's genitalia to know for certain. The single specimen Megan collected is alive and well as we speak.

Occupied tarantula burrow

Bell has a keen eye for detecting tarantula burrows, which are surprisingly small and cryptic, hidden among tangles of desert grassland vegetation. Occupied burrows are covered with a thin film of silk by day. Sometimes, the remains of insect prey are scattered around the burrow entrance, too. Still, it takes skill to spot the holes.

Bell "fishing" for a tarantula while Heidi looks on

It takes even *more* skill to "fish" the occupant from her lair. Bell is highly skilled at this, and Jordan was able to capture the procedure in a video. Everyone was shocked to see such a large arachnid erupting from such a small tunnel. Whether a given spider is mature or not is difficult to assess. Male specimens change drastically in appearance upon their final molt into maturity, but females do not; and tarantulas are among the very few spiders that continue to molt after they reach adulthood.

Megan admiring the spider that Bell fished out
Megan's tarantula up close (© Megan Miller)

Upon returning home, Megan set up a spacious terrarium to house her new friend. Since tarantulas are in high demand in the pet trade, we agreed that we would not disclose the exact location that we visited. We thank Ryan for sharing his "spot" even with us. Thank you for trusting!

Megan's tarantula (© Megan Miller)

We found three occupied burrows altogether, but could only lure the one spider out. We did find other kinds of spiders, though. Before we had even ventured from the vicinity of our parked cars, we came across a lovely orange jumping spider, Phidippus apacheanus. It is thought that this species might mimic velvet ants, wingless female wasps that pack a very painful sting. They certainly share the wasp's bright "warning colors" of black and orange.

There were also Western Black Widows, and two kinds of orbweavers. This Banded Garden Spider, Argiope trifasciata was a highlight of the trip. Despite her size she was difficult to spot in her web in dense, tall grass.

Banded Garden Spider

Heidi had an easier time noticing another giant, a female Black and Yellow Garden Spider, Argiope aurantia. This species seems to prefer slightly more "open" situations, but still build their webs relatively close to the ground. Both species of Argiope can easily handle grasshoppers and other large, strong prey that become entangled in their snares.

Black & Yellow Garden Spider

Grasshoppers certainly were plentiful, and diverse. They scattered at every step: Carolina Grasshopper (Dissosteira carolina), Two-striped Grasshopper (Melanoplus bivittatus), and Two-striped Mermiria (Mermiria bivittata) being among the most conspicuous. I also finally got images of the Ebony Grasshopper, Boopedon nubilum, and Saussure's Blue-winged Grasshopper, Leprus intermedius. Black-winged Grasshoppers, Trimerotropis melanoptera,also made an appearance.

Leprus intermedius with hind wing spread

As we were leaving, Jordan suddenly jumped and exclaimed that a very large insect had collided with him after it leapt from the ground beneath his feet. Upon investigating we found a spectacular female specimen of the Green Bird Grasshopper, Schistocerca shoshone. This was the first one I have seen in Colorado.

Green Bird Grasshopper

We concluded our expedition with a well-earned visit to the Dairy Queen back along the interstate at Pueblo. As we sat down I noticed a small spider on the outside of the window. Tired and hungry, I nearly dismissed it as "just another orbweaver." I am glad I took time to double check. It was a mature pirate spider, family Mimetidae, perhaps Reo eutypus, though I can't be positive. You just never know *what* you will find, or where you will find it! Many thanks to my partners in crime. You all rock.

Pirate Spider from Dairy Queen

Wednesday, September 23, 2015

Makin' Paper

This has been an exceptional year for paper-making social wasps in the family Vespidae here along the Colorado Front Range. Most species of paper wasps and yellowjackets have been unusually abundant, much to the consternation of the average person who despises any stinging insect. However, there is much to admire about these industrious organisms, not the least of which is the amazing architecture of their nests.

Western Paper Wasp nest (Mischocyttarus flavitarsis)

Nests of most social vespids are made of repurposed or recycled cellulose from dead, woody plants and trees. The wasps manufacture the paper by scraping fibers and chewing them into a ball of pulp that is taken back to the nest and applied as a thin strip that soon dries into a surprisingly durable, stiff material.

Bald-faced Hornet worker scraping wood fibers

Paper wasps in the genera Polistes and Mischocyttarus here in Colorado make exposed paper combs that are frequently suspended under the eaves of buildings. Yellowjackets, including the Bald-faced "Hornet," Dolichovespula maculata, house their combs within a layered paper envelope. Species in the genus Dolichovespula build their nests above ground, usually in a tree, shrub, or among berry canes. Species in the genus Vespula normally build their nests underground in abandoned rodent burrows and other pre-existing cavities that they can expand by excavating around the nest.

Huge European Paper Wasp nest

I was surprised to find out that paper wasps will re-use old nests! One particularly impressive nest of European Paper Wasps (Polistes dominula) is situated under an overhang at my workplace in Colorado Springs. It appeared abandoned when I first started work there, but was quickly occupied and even expanded later in the season. This is an impressively large nest that would probably not fit on a dinner plate, very unusual for any species of Polistes.

Active nest of Bald-faced Hornets

I also discovered an active nest of the Bald-faced Hornet in North Cheyenne CaƱon on August 21. Fortunately, it was far enough off the trail to not be a potential hazard to the many people that use the park; and far enough off the trail to make it difficult for anyone to destroy the nest. I went back a month later (September 18) and found the wasps had expanded the nest and changed its shape from oval to a roughly football shape. There was no evidence of activity, and indeed the colony cycle for this species is shorter than that of other social wasps.

Bald-faced Hornet nest on August 21
The same nest on September 18

Underground nests like that of the Western Yellowjacket (Vespula pensylvanica) and Prairie Yellowjacket (V. atropilosa) are more problematic because one can easily disturb an unseen nest with painful results. I only notice nests when my eye catches a steady stream of yellowjackets coming and going from a common point.

Western Yellowjacket nest entrance. Note exiting workers carrying soil pellets

Paper wasps are generally welcome predators of caterpillars and other soft-bodied insect pests. The Bald-faced Hornet is a predator of flies that is never a pest at picnics and barbecues. The same is true of the Prairie Yellowjacket. Meanwhile, the Western Yellowjacket is a scavenger that will take your lunch away from you given the opportunity. Gently waving your hand can eventually discourage the wasp's efforts.

Prairie Yellowjacket worker eating insect

We may have these wasps to thank for inspiring the invention of the paper that we use today. At least some accounts trace observations of wasps in ancient China to the origins of human papermaking.