Bug of the Month!

Common name: Snowy tree cricket

Latin name: Oecanthus fultoni

Taxonomy:
Kingdom Animalia
   Phylum Arthropoda
      Class Insecta
         Order Orthoptera
            Family Gryllidae
 

Crickets in general
The crickets (Family Gryllidae) are a group of insects within the order Orthoptera (literally, “straight wing”). The Orthoptera include the grasshoppers, crickets and katydids. All Orthopterans have two pairs of wings.  The front pair is hardened and leathery. When the insect is resting, this pair covers the inner second pair, which is membranous. In flighted species, the second pair is used for flight. Orthopterans have large compound eyes and long, powerful hind legs which are used for jumping. Many of them produce sounds by stridulation—rubbing one body part against another.

Crickets (the family Gryllidae) can be distinguished from grasshoppers by the fact that crickets have long antennae, while grasshoppers have short ones. Also, most crickets are nocturnal (active at night), while most grasshoppers are diurnal (active during the day). The cricket family includes three subfamilies: field crickets, ground crickets, and tree crickets. Worldwide, there are about 3,800 species, and in North America, about 100 species.

Crickets are good singers. In general, female crickets cannot produce sound, but male crickets can stridulate. They rub the bottom of their left wing against the top of the right wing to produce a chirping or trilling sound, which attracts females. Each cricket species has a unique song. Crickets can hear with “ears” situated on their front legs.

There are many myths about crickets. In Asia, they are considered to be good luck and are kept as pets. People also stage and gamble on cricket fights, especially in Asia. In Brazil, cricket song is believed to foretell rain or the coming of a large sum of money. Some people in Africa and Asia eat crickets as food; they are frequently regarded as a delicacy.

How to identify snowy tree crickets
Like most other tree crickets, snowy tree crickets have slender bodies, long, hair-like antennae, and are pale green in color. They are usually found on bushes and trees. Males have broad, clear wings; females wings are narrower and are held tightly against their bodies. Snowy tree crickets measure 15-18 mm (~3/4 inch) from the tip of the head to the tip of the abdomen.

Several other tree cricket species look very similar to the snowy tree cricket, including the narrow winged tree cricket, the black-horned tree cricket, and Davis’ tree cricket. To distinguish the snowy tree cricket from other species, look at the first two segments at the base of the cricket’s antennae. Under a magnifying glass or dissecting microscope, you can see black markings. Snowy tree crickets have one round, black spot on the first segment and one on the second segment. 

Probably the easiest way to identify a tree cricket is by its very distinctive song. The snowy tree cricket is also known as the “thermometer cricket” because its chirping can be used to tell the temperature. To find the temperature in degrees Fahrenheit, count the number of chirps in 13 seconds and then add 40.

Above: A spectrogram of a snowy tree cricket's song, recorded in the lab by Alison Ravenscraft.
A spectrogram is a visual representation of sound. Time (in seconds) is on the horizontal axis, the pitch of the sound (in frequency, kHz) is on the vertical axis, and volume is represented by the darkness of the gray shading
 

Recordings:

Calf Island
Lab
Thompson Island

What do you think the temperature was when each of these recordings was taken? Can you hear the snowy tree cricket among the other singing insects in the Thompson Island recording? (Please note: all are MP3 files and may open your music player. Alternately, right-click or control-click to download)

 
Where to find snowy tree crickets on the Boston Harbor Islands
Snowy tree crickets live in trees and bushes and even brambles like raspberry. They especially like broadleaved trees, such as oaks. These insects are hard to spot because they are well-camouflaged and nocturnal. However, they are very common and their singing can be heard in the evening and at night from July through October.

How snowy tree crickets make a living
Snowy tree crickets prefer vegetation with broad, deciduous leaves. During the day snowy tree crickets hide and rest, but at night they roam over leaves and branches in search of food and mates. They are omnivorous and will eat a wide range of plants and small insects, including aphids.

Snowy tree crickets, like all orthopterans, are hemimetabolous. In the fall, females use their long ovipositors (see photo above) to drill into twigs and plant stems and lay their eggs inside. These eggs overwinter, and then in the spring they hatch into nymphs. The nymphs mature through five stages, known as instars, before they become adults. At the end of each instar they shed their skin. With each molt, they resemble an adult more and more. Mature tree crickets appear in July and can be found through October.

Beginning in July, when they have reached adulthood, male snowy tree crickets sing to attract females. Their melodious chirping is well-known and loved as a characteristic sound of nighttime in late summer. Males often synchronize their calls and sing together, a phenomenon known as “chorusing.”

Where in the world snowy tree crickets occur
Snowy tree crickets are common and widespread. They live in most of the USA, except for the southeastern states.

To learn more about snowy tree crickets (and crickets in general)

On the web:

“Snowy Tree Cricket.” Singing insects of North America, website. http://buzz.ifas.ufl.edu/585a.htm

“Snowy tree cricket.” The songs of insects, online species profile. http://www.musicofnature.com (click for direct link to species page)

Fulton, B. B. 1915. The tree crickets of New York: life history and bionomics. Technical Bulletin for the New York Agricultural Experiment Station. http://buzz.ifas.ufl.edu/s576lf15.pdf

Bland, R.G. 2003. The orthoptera of Michigan—biology, keys, and descriptions of grasshoppers, katydids, and crickets. Michigan State University Extension, Extension Bulletin E-2815. 

Elliot, L. and W. Hershberger. 2007. The songs of insects. Houghton Mifflin, Boston. (includes a CD of many singing crickets and katydids)

Related: Orthopteran Song on the Boston Harbor Islands