OrThoptera Thursday: Lesser Angle-wing Katydid

Last week I wrote about the Greater Angle-wing Katydid, a common species over much of the U.S. While reviewing images for that post, I discovered I also had images of its cousin, the Lesser Angle-wing Katydid, Microcentrum retinerve, from the same location in south-central Ohio.

The Lesser Angle-wing, as its name suggests, is a smaller animal, adults ranging from 44-53 millimeters in length compared to the 52-63 millimeter Greater Angle-wing. Males of Microcentrum retinerve have the stridulatory area consistently brown in color, a sharp contrast to the bright green of the rest of the insect. I also find that Lesser Angle-wing Katydids have the veins of the front wing more explicitly defined than in the Greater Angle-wing, making the creature even more convincing as a leaf mimic. This rougher texture is not always a defining character, but it helps.

The key character in separating these two species of Microcentrum would naturally be the most difficult to capture from images of wild, living specimens. The front edge of the pronotum (top of thorax) is smooth and straight in M. retinerve. This front margin has a very small, central tooth in M. rhombifolium.

Both species occupy the same kind of deciduous forest habitat, but the Lesser Angle-wing Katydid has a more restricted range. It occurs from Long Island and New Jersey south to northern Florida and west to Missouri and extreme east Texas and Oklahoma.

Locating a singing male can be highly frustrating, as the interval between songs is even longer than in the Greater Angle-wing; and they don’t have a “courtship song” of repeated tics. Each call is a rapid series of 3-5 pulses, too fast to count (but revealed visually in sonagrams), repeated about once per second for a short period.

Look for the adults at the tips of branches on trees at night. It is actually easier to see them in a flashlight beam than during the day because they are more active, and stand out vertically against the otherwise horizontal plane of foliage. Moving katydids are always easier to spot than stationary ones.

The Lesser Angle-wing Katydid will also fly to lights at night, which is how I obtained these few images. I am still not absolutely certain that the female is not actually a Greater Angle-wing specimen. It was climbing high on the wall and windows of a building and I could not gauge its size accurately, let alone note whether there was a tooth on the front edge of the pronotum.

Adults are most commonly encountered between late July and mid-October, but depending on latitude they may reach maturity as early as May. Other facets of behavior and life cycle are essentially identical to those of the Greater Angle-wing Katydid.

Sources: Capinera, John L., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca: Comstock Publishing Associates (Cornell University Press). 249 pp.
Elliott, Lang and Wil Hershberger. 2007. The Songs of Insects. Boston: Houghton Mifflin Company. 228 pp.

Moth Monday: California Oak Moth

Welcome to the first post in a semi-regular feature I call “Moth Monday.” When possible I will include images of the adult, caterpillar, and pupa stages. I will strive to update previous posts if I am able to obtain images of adults or larvae that I did not have at the time of the original posting. Note that this feature is irregular in part because my family’s “weekend” is Sunday and Monday rather than Saturday and Sunday.

Rarely am I able to complete the life cycle of any insect in images, even over months if not years, let alone in one day at one location, but this improbable event occurred on March 25, 2011 in Carpinteria, California. My wife and I (we were dating at the time) were visiting her uncle and his wife, and strolling the neighborhood we came across one tree that was full of every life stage of the California Oak Moth, Phryganidia californica.

This species is legendary for its periodic population outbreaks that can, in epidemic years, result in the complete defoliation of oak trees along the California coast. California Live Oak, Quercus agrifolia, is the preferred host, but other species are on the menu. Incidental hosts include eucalyptus, chestnut, Tan Oak (Lithocarpus densiflorus), and azalea. The California Oak Moth also occurs in southwest Oregon where it eats Giant Chinkapin (Castanopsis chrysophylla) and Canyon Live Oak, as well as Tan Oak.

Despite the visually devastating effects of its caterpillars, the moth is rarely, if ever, responsible for the outright death of trees. We tend to severely underestimate the resilience of plants in general to withstand the attacks of insects and other herbivores.

Female moths lay their eggs in loose clusters on the foliage, limbs, or trunks of the host. Eggs laid on the underside of leaves late in the season are often able to overwinter there.

The caterpillars that hatch begin skeletonizing the leaves, grazing on the tissue between veins on the undersurface.

Older caterpillars are eventually able to consume all but the major leaf veins. The caterpillars undergo five molts, eventually reaching about 25 millimeters in length before they pupate.

The pupa may be mistaken for a butterfly chrysalis, as there is no silken cocoon encasing it, and it is boldly marked in black and white or yellow. Pupae are generally suspended by silken threads from the host tree or any vertical object close by.

The caterpillars and/or pupae are hosts themselves for a number of parasites. Among them are the tachinid flies Actia flavipes, Hyphantrophaga virillis, and a species of Ceranthia. An ichneumon wasp in the genus Mesochorus is also recorded from California Oak Moth caterpillars (Carmean, Miller, and Scaccia, 1989). There is also a nuclear polyhedrosis virus (NPV) and a fungus (Beauveria bassiana) that kill the caterpillars. The virus leaves the caterpillars hanging as limp, lifeless brown corpses from foliage, while the fungus may manifest itself as a white, powdery coating on the larvae, with an unpleasant odor as an accompaniment (S. Swain, et al., 2012).

The adult moths are dull brown, with a wingspan varying from 25-35 millimeters. They fly weakly, but well enough to disperse effectively. Males have pectinate (comb-like) antennae, the better to locate a female by the pheromones (scents) she releases to attract potential mates. Rarely do these moths fly to lights at night. You are much more apt to see them randomly during daylight hours in places where populations are abundant.

The California Oak Moth is also known as the California Oakworm, which is perhaps a better name since it is the caterpillars that do the damage. Formerly placed in its own family, the Dioptidae, it has recently been reclassified as one of the “prominent” moths in the family Notodontidae (subfamily Dioptinae).

Anyone living in the western half of California, from the Oregon state line to the Mexican border, is likely to encounter this species. During population booms it finds its way inland from the coast to central valleys. There are two generations each year in northern California, and three generations per year in southern California.

Sources: Carmean, David, Jeffrey C. Miller, and Brian Scaccia. 1989. “Overwintering of Phryganidia californica in the Oregon Cascades and Notes on its Parasitoids (Lepidoptera: Dioptidae),” Pan-Pac. Entomol. 65(1): 74-76
Essig, E.O. 1958. Insects and Mites of Western North America. New York: The Macmillan Company. 1050 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. Washington, DC: U.S. Department of Agriculture Forest Service Miscellaneous Publication No. 1339. 654 pp.
Powell, Jerry A. and Charles L. Hogue. 1979. California Insects. Berkeley: University of California Press. 388 pp.
Swain, S., S.A. Tjosvold, and S.H. Dreistadt. 2012. “Pest Notes: California Oakworm,” UC IPM Online.

OrThoptera Thursday: Greater Angle-wing Katydid

One of the joys of summer nights in North America, at least east of the Rocky Mountains, is the songs of katydids. Among the more abundant and widespread of our many native species is the Greater Angle-wing Katydid, Microcentrum rhombifolium.

This is a very large insect, adults reaching 52-63 millimeters from head to folded wingtip. Females in particular are also very heavy. Let one crawl across your hand and you will feel how weighty she is. Both genders are uniformly green throughout, somewhat mottled on the legs and face. This species is among the most “leaf-like” of our katydids and is found mostly in deciduous trees.

The Greater Angle-wing ranges from Pennsylvania and New Jersey south to Florida, west to southeast Minnesota, Iowa, southeast Nebraska, Kansas, and Texas. It also wraps around the southern tip of the Rockies and Sierras, north to San Francisco Bay and throughout Arizona and much of Utah.

Adult males of this species produce two kinds of songs. The first is a “calling song” that consists of a loud “lisp” repeated an average of every two to four seconds. Producing an intermittent song like this probably prevents predators from easily locating the insect. I know it has frustrated me on a number of occasions and I have better than average hearing. Once a female is attracted, the male switches to a “courtship song” that is a series of “ticks.” The female is capable of answering this call, though she does not have the well-defined sound-producing structures the male has. The male eventually moves to find the female via this “conversation.”

Contrary to popular culture, katydids do not generate their song by rubbing their legs over their wings. The front wings of the male are modified at the “shoulders” to include a file on one wing and a scraper on the other. The file is composed of a row of peg-like teeth over which the scraper is stroked rapidly. This method of sound-production is termed “stridulation,” and the part of the wing modified is called the “stridulatory area.” Both genders hear the songs through slit-like openings on the front legs.

Once male and female are together, mating may take place. This involves the transfer of a sperm packet known as a spermatophore, produced by the male. The spermatophore is a fairly substantial ball of gelatinous protein surrounding the sperm sac itself. Once the pair disengages, the female will eat the protein mass while the sperm enter her oviduct.

The first time I witnessed mating in katydids, I thought something horrible had happened to the female, that her internal organs were oozing out of her body! The edible gift provided by the male may help foster the development of her eggs, and/or encourage her to rebuff subsequent suitors, thereby insuring it is his DNA that is carried through to the next generation.

One additional, odd note. I observed a trio of Greater Angle-wing Katydids in south-central Ohio in August of 2011 that puzzled me. One of the two females appeared to be licking the back of the male’s abdomen (see image above). I am aware that male tree crickets produce glandular secretions from the thorax near the base of their wings, but I am not familiar with an analogous situation in katydids. However, I did find other references to this behavior (Fulton, 1933; Gwynne, 2001), likewise without explanation.

Mated females deposit their eggs single-file along a twig or the edge of a leaf, each ovum overlapping the last like shingles on a roof. The eggs are vulnerable to parasites, chiefly tiny wasps in the family Eupelmidae.

The nymphs that hatch feed generally on foliage, and molt four times before reaching adulthood. While it is difficult to identify most katydids in the nymphal stage, the robust body shape, relatively short hind legs, and mottled green appearance of Microcentrum nymphs helps them to be easily separated from other North American katydid genera.

Both large nymphs and adults can be preyed upon by a number of other animals, and especially by sphecid wasps like the Great Black Wasp. Adults can fly when pressed to do so, but generally creep about slowly so as not to draw attention to themselves in the first place.

Look for the Greater Angle-wing Katydid along forest edges, in gardens and yards, even in lone trees in open fields. They are also attracted to lights at night, though not in great numbers. The best way to find them is at night, with your ears and a good flashlight. Good luck.

Sources: Capinera, John L., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca: Comstock Publishing Associates (Cornell University Press). 249 pp.
Elliott, Lang and Wil Hershberger. 2007. The Songs of Insects. Boston: Houghton Mifflin Company. 228 pp.
Fulton, B.B. 1933. “Stridulating Organs of Female Tettigoniidae (Orthoptera),” Entomol. News 44: 270-275
Gwynne, Darryl T. 2001. Katydids and Bush-Crickets: Reproductive Behavior and Evolution of the Tettigoniidae. Ithaca: Comstock Publishing Associates (Cornell University Press). 317 pp.

True Bug Tuesday: Mirid plant bug

You can’t judge a book by its cover, and you can’t identify most insects by color pattern alone. One perfect example of this is a colorful plant bug, Metriorrhynchomiris dislocatus, in the family Miridae.

I first encountered this species in South Deerfield, Massachusetts on June 7, 2009 (image above). I discovered several more in the Forest Preserve System surrounding Chicago, Illinois and its suburbs in late June, 2011. The species is common throughout the eastern U.S. and adjacent Canada, west to Alberta and Colorado, and south to Florida and Texas.

This is an average-size insect for the typical mired plant bug, if not a little on the large side, adults measuring 6.5 millimeters.

What is confounding about this species is its seemingly infinite variability in color pattern. No less than fifteen different color forms have been recorded, with no connection to geographic location. The entomologist Willis Stanley Blatchley (1859-1940) called such true bug species “spotted dogs,” and resisted the urge to consider each variation as a separate subspecies. This diversity in appearance is called “color polymorphism,” and it is not uncommon in the Miridae as a whole.

One is likely to encounter M. dislocatus on a fair number of different plants, but it is demonstrably associated with False Solomon’s Seal (Smilacina racemosa) and Wild Geranium (Geranium maculatum), especially in shady, moist woodland habitats. Additional plant associations that are probably not host plants include American Fly Honeysuckle (Lonicera Canadensis) in Quebec, Canada; Star-flowered Lily-of-the-Valley (Maianthemum stellatum) in Wisconsin; Kentucky Bluegrass (Poa pratensis) in Pennsylvania; Maryland Black Snakeroot (Sanicula marilandica) in Kansas; and grape (Vitis sp.) in Ontario, Canada.

This species is also a “flower visitor,” obtaining nectar from various plants. Records from Illinois show that M. dislocatus has been seen on blossoms of Canadian Horseweed (Conyza Canadensis), Philadelphia Fleabane (Erigeron philadelphicus), Smooth Oxeye, (Heliopsis helianthoides), Canada Goldenrod (Solidago canadensis), and Early Goldenrod (S. juncea) (Hilty, 2013). They have also been observed on the male flowers of Revolute Meadowrue (Thalictrum revolutum) in Pennsylvania (Wheeler, 2001). Adults are found mostly between April and July, depending on latitude.

Host plant associations are important in helping to identify most mirids, but there are many gaps to fill in as far as host records go. Furthermore, some mirids are predatory rather than phytophagous (plant-feeding), so host plant records are mostly irrelevant. Keeping track of the plants you observe mirids on is still an important exercise. Happy hunting.

Sources: Eaton, Eric R. and Kenn Kaufman. 2007. Kaufman Field Guide to Insects of North America. Boston: Houghton Mifflin Company. 392 pp.
Gregorev, Nina, et al. 2011. Plant Bug: Planetary Biodiversity Inventory.
Hilty, John. (edit.). 2013. Insect Visitors of Illinois Wildflowers. (Illinoiswildflowers.info)
Pickering, John, et al. 2013. Discover Life.
Slater, J.A. and R.M. Baranowski. 1978. How to Know the True Bugs. Dubuque, Iowa: Wm. C. Brown Company Publishers. 256 pp.
Watson, S.A. 1928. “The Miridae of Ohio,” The Ohio State University Bulletin 33(4): 44 pp. (Ohio Biological Survey Bulletin 16, vol. IV, no. 1).
Wheeler, Alfred George, Jr. 2001. Biology of the Plant Bugs (Hemiptera: Miridae): Pests, Predators, Opportunists. Ithaca: Cornell University Press. 507 pp.