ARTHROPOD MUSEUM NOTES
Number 26 • October 20, 2003 • Jeffrey K. Barnes
Genus and species: Pterophylla camellifolia (Fabricius)
True katydids are flightless or nearly flightless inhabitants of crowns of deciduous trees in oak-hickory forests, parks, and yards. They are leaf green in color and range in length from 1.5 to 2.5 inches. The hind wings are shorter than the leathery, convex, and inflated front wings, which act as coverings known as tegmina. The green tegmina have prominent veins that closely mimic a leaf, including the midrib, and they enclose the abdomen. Most calling males seem to remain at approximately the same place in a tree throughout adult life. Individuals that are disturbed leap clumsily and parachute down to the ground. On the ground they are awkward and slow. They walk to a vertical surface, which they climb. During the first severe frosts of late autumn, they often fall to the ground (Hebard 1941, Shaw 1975).
True katydids occur from southern New England to northern Florida and west to Iowa and eastern Texas. Outlying individuals or populations, probably representing inadvertent introductions or range extensions, have been found recently in North Dakota (Balsbaugh 1988) and Colorado (Weismann and Leatherman 1992). The species is strictly arboreal in deciduous trees, so its distribution is discontinuous.
There are several distinct populations of Pterophyla camellifolia, differing in song and morphology and separated by zones of intergradations (Alexander 1968, North and Shaw 1979). Hebard (1941) recognized three subspecies of P. camellifolia: P. c. camellifolia from the eastern United States west to eastern Kansas, P. c. intermedia (Caudell) from the Gulf Coast of Mississippi probably west to extreme eastern Texas, and P. c. dentifera Hebard from southwestern Arkansas. Pterophylla c. camellifolia seems to have of further racial subdivisions with northern, southeastern, and southwestern ranges. The true katydid may have differentiated during the Pleistocene. Postglacial northern migration of oak-hickory forests and their associated faunae have facilitated contact between disparate populations (North and Shaw 1979).
In northern states, most chirps are disyllabic or trisyllabic, but in southern states most chirps have at least four syllables and frequently as many as seven. This is because in northern states the wingstroke rate is a little more than half that in southern states. Since the male’s calls are produced using wingstrokes to strike a stridulatory scaper in the base of one front wing over a file on the base of the other front wing, there is geographic variation in the sounds produced (Alexander 1968).
The ovipositor is almost as long as the abdomen, and it resembles a curved knife. Females have been found ovipositing low on the trunk of a small elm tree, and in captivity, eggs have been inserted into a piece of cork and into crevices in the breeding cage. Under natural conditions, eggs are probably inserted into bark near treetops. The eggs are dark slate-gray, a quarter inch or more in length, over three times as long as wide, flat, pointed at each end, with the edges bevelled. They are held in crevices with adhesive, often several pressed close together (Riley 1873, 1874; Caudell 1906). The young feed on leaves and probably rarely or never leave the tree on which they start life. They mature and start calling in July, and they are killed by the heavy frosts of October or November.
Males of most katydid species call acoustically to attract females. Individuals hear the calls with tympanal devices on their front tibiae. Male true katydids produce loud, raucous, chirping sounds at night with their forewings. The sound producing stridulatory apparatus consists of an upwardly directed sclerotized scraper on the base of the right forewing, which is rubbed along the row of teeth of the file on the lower surface of the base of the left forewing. Each wing stroke produces a pulse of sound in a katydid’s chirp. The male’s calling sound is a regular repetition of loud, coarse, multi-pulse chirps or phrases.
The distinctive nighttime song of Pterophylla camellifolia long ago provided the inspiration for the common name “katydid,” which is now applied generally to the long-horned grasshopper family Tettigoniidae in North America and some other parts of the world. In Europe, the tettigoniids are called bush crickets. Harvard librarian Thaddeus William Harris (1842) wrote in the early 18th century, “At the approach of twilight the katy-did mounts to the upper branches of the tree in which he lives, and, as soon as the shades of evening prevail, begins his noisy babble, while rival notes issue from the neighboring trees, and the groves resound with the call of ‘katy-did, she-did’ the live-long night.” As Caudell (1906) recalls, the sound is very loud, but the resemblance to the words kady-did and she-did is merely fanciful. Morgan Hebard (1941) described the sound differently. “The song of this insect consists of two to five (usually three) exceedingly loud but pleasantly resonant notes, incessantly repeated, from which song the name “Katy-did” was undoubtedly derived. The sound has been described as ‘xr -, excessively rasping and grating”… To me it is quite the reverse, exceptionally pleasing…, embodying a resonant fullness and enthusiasm which brings to mind leafy treetops on clear Summer nights.”
Males alternate chirps when they are not more than 25 to 50 feet from one another. When two chirping males are close together, say within 2-3 feet, they lengthen their chips, and the alternation of lengthened chirps is termed aggressive sound. Aggressive chirping stimulates the other male to stridulate in the same way or to stop stridulating and leave the area (Shaw 1968).
True katydid females are also capable of stridulating, but apparently they do so only when disturbed by handling. The disturbance sound is a soft rustling produced by a stridulatory apparatus markedly different from that of the male (Caudell 1906, Fulton 1933). Handling also elicits arrhythmic disturbance sounds from males (Shaw 1968).
Alexander, R. D. 1968. Arthropods. Pages 167-216 in T. A. Sebeok, ed., Animal communication. Indiana University Press, Bloomington, Indiana.
Balsbaugh, E. U. First record of the true katydid, Pterophylla camellifolia (Orthoptera: Tettigoniidae: Pseudophyllinae) in North Dakota. Great Lakes Entomologist 21 (2): 91.
Caudell, A. N. 1906. Class I, Hexapoda. Order XI, Orthoptera. The Cyrtophylli of the United States. Journal of the New York Entomological Society 14: 32-45.
Fulton, B. B. 1933. Stridulating organs of female Tettigoniidae. Entomological News 44: 270-275.
Harris, T. W. 1842. A treatise on some of the insects of New England, which are injurious to vegetation. John Owen, Cambridge, Massachusetts.
Hebard, M. 1941. The group Pterophyllae as found in the United States (Orthoptera: Tettigoniidae). Transactions of the American Entomological Society 67: 197-219.
Helfer, J. R. 1953. How to know the grasshoppers, cockroaches and their allies. Wm. C. Brown Company Publishers. Dubuque, Iowa.
North, R. C., and K. C. Shaw. 1979. Variation in distribution, morphology and calling song of two populations of Pterophylla camellifolia (Orthroptera: Tettigoniidae). Psyche 86: 363-374.
Riley, C. V. 1873. Eggs in and on canes and twigs. Annual Report on the Noxious, Beneficial, and Other Insects of the State of Missouri 5: 119-125.
Riley, C. V. 1874. Katydids. Annual Report on the Noxious, Beneficial, and Other Insects of the State of Missouri 6: 150-169.
Shaw, K. C. 1968. An analysis of the phonoresponse of males of the true katydid, Pterophylla camellifolia (Fabricius) (Orthoptera: Tettigoniidae). Behaviour 31: 203-260.
Shaw, K. C. 1975. Environmentally-induced modification of the chirp length of males of the true katydid, Pterophylla camellifolia (F.) (Orthoptera: Tettigoniidae). Annals of the Entomological Society of America 68 (2): 245-250.