common tree crickets
||Key to genera of tree crickets (Oecanthinae).
||Key to species groups of Oecanthus (common tree crickets).
For a beauthifully illustrated, informative website devoted mostly to Oecanthus, go to http://www.oecanthinae.com/. This site, created by Nancy Collins (an energetic oecanthine enthusiast), is organized into more than 20 sections and has impressive still photos and videos.
North American species of Oecanthus fall into four groups based on numerous characters including markings and swellings on the first and second antennal segments and male-limited characters such as calling songs, proportions of the dorsal field of the forewings, and features of the metanotal glands. (These glands, sometimes termed "honey pots," are exposed during calling and courtship. After the female mounts the male to receive a spermatophore, she spends 5-15 minutes feeding on the secretions of these glands.
[insert Fulton's drawing, and plate showing glands of the four groups.]
Identification of species
First determine the species group by using the pictorial key. From there you will be linked to the appropriate section below.
rileyi species group
Three species belonging to this group occur within the area covered by SINA. O. fultoni, the snowy tree cricket, occurs widely, but not in the Southeast and far-northern areas. O. rileyi, Riley's tree cricket, is known only from Arizona and the states bordering the Pacific. Differences in the markings on the first two antennal segments easily separate these two species in nearly all cases. The third species is known in the U.S. only from the lower Rio Grande valley and has only recently been formally described.
|Variation in the antennal markings of the two species in the rileyi group. In each group of three drawings, the two on the left are representative of the markings of most specimens of the species.
niveus species group
The three species belonging to this group are easily identified on the basis of the markings on the first two antennal segments. O. niveus (narrow-winged tree cricket) has a J-shaped mark on the first antennal segment; O. exclamationis (Davis's tree cricket) has a broad straight mark on the first antennal segment, which becomes part of an exclamation mark when viewed with the the mark on the second segment; and O. leptogrammis (thin-lined tree cricket) has narrow straight lines on the first and second antennal segments.
nigricornis species group
Most members of this group occur predominantly in herbaceous vegetation and hence are more readily collected than tree-inhabiting tree crickets. However, two species inhabit coniferous trees and their color, as well as their habitats, set them apart (see below). The two conifer-inhabiting species, O. pini (pine tree cricket) and O. laricis (tamarack tree cricket), can be recognized by their brown heads and thorax and green or green-tinged wings, which make them difficult to spot when they rest with their heads next to the boughs with their rears amidst the needles. The two species are known almost exclusively from pines and tamarack respectively, but O. pini has been collected on balsam fir in southeastern New York and O.laricis on hemlock in northeastern Ohio.
The herb-inhabiting species of the nigricornis group are sometimes difficult to identify, and they exhibit interesting and poorly understood variations in the plants they inhabit. In the case of O. nigricornis (black-horned tree cricket) and O. forbesi (Forbes's tree cricket), the only identifying feature is the (temperature-dependant) pulse rate of the male calling song. This makes females and dead males identifiable only by their association with males of known song type--and sometimes, at least in central Ohio, the two species occur together. That said, with the exception of nigricornis vs. forbesi, the markings on the first two antennal segments provide a good means of identifying most specimens of the herb-inhabiting species of the nigricornis group.
|Variation in the antennal markings of the herb-inhabiting species in the nigricornis group. In each group of four drawings, the two at center are representative of the markings of most specimens of the species.
It is important to understand that when these herb-inhabiting species are collected by sweeping a net through the vegetation on which they occur, two or even three species may be among the catch. When the two are O. quadripunctatus (four-spotted tree cricket) and O. celerinictus, as in the Southeast, or O. quadripunctatus and O. argentinus (prairie tree cricket), as in the Midwest, there is little to suggest that more than one species is present until the antennal marks are examined. On the other hand when the two are quadripunctatus and nigricornis, as in the Northeast, the differing overall coloration of the two separates the two without reference to the antennal markings. In this regard, it must be noted that the overall coloration of nigricornis and forbesi is often intermediate between the first two of the three color modes illustrated above.
It should also be noted that the herb-inhabiting species of the nigricornis group are sometimes found on woody plants. Males may call from the lower branches of small trees in open areas, and in some cases both sexes seem at home on woody plants such as willow and sumac.
varicornis species group