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Subfamily Copiphorinae in North America north of Mexico

Coneheaded katydids are medium-to-large (24-74 mm), grasshopper-like insects with oversized jaws. They are the only katydids that have the head produced into a pointed or rounded cone that projects beyond the basal antennal segments. Most species have long, narrow forewings and, with the aid of the concealed hindwings, are strong fliers; a few species have abbreviated forewings and are flightless. Four genera and 22 species occur in America north of Mexico. All occur in the eastern United States and only 3 species have been found west of Texas.

Brown/green color dimorphism

All U.S. coneheads occur in two color phases: brown and green. Except for Pyrgocorypha uncinata, in which no green males are known, both males and females are dimorphic. In two other species (Neoconocephalus triops and Bucrates malivolans) the green phase is much rarer among males than females. In most species the proportions of the two phases are similar for the two sexes, but the proportions vary widely among species and among series of the same species collected at different places and at different times. No one has carefully studied the occurrence of brown and green phases in any species of conehead. Such a study would require collection or observation of large numbers of individuals at different places and times by methods that were not biased by the color of the individuals that might be collected or observed.

Little is known of the adaptive significance or the genetic and environmental determinants of the color phases. The adaptive significance is most likely related to protection from diurnal, visually hunting predators, such as many species of birds. Experiments have shown that when such a predator has fed upon prey of one color, it is less likely to capture another individual of the same species if that individual is of a different color. The merits of a conehead being brown or green thus depend not only on the color of the individual's surroundings, which are generally brown and green, but also upon the color of its neighbors and the previous experiences of its visually hunting predators. Anyone who searches for coneheads visually will soon confirm that it is difficult to look for brown and green individuals simultaneously, that the color sought is influenced by the color of previous captures, and that individuals of the other color are less likely to be detected.

Individuals sometimes change color during their development. For instance, all early juveniles of Neoconocephalus and Belocephalus are green, a few become brown during molts to late juvenile instars, and the majority of those that become brown adults change during the final molt. Apparently no one has recorded a conehead molting from brown to green.

J.J. Whitesell (1974) showed that the color of male Neoconocephalus triops is influenced by photoperiod. Green nymphs exposed to 11-hour photoperiods molted to brown adults whereas those exposed to 15-hour photoperiods produced both green and brown adults. Under natural conditions this results in winter males being brown and summer males being dimorphic.

Oviposition

The ovipositors of coneheads are slender, nearly straight, and bear no teeth. Bucrates malivolans, with a blade 35-45 mm long, has the most spectacular egg-laying tool of any U.S. katydid. It and other species that have been seen ovipositing insert their eggs between the stems and sheaths of root leaves of cattails or grasses. Whitesell (1969) reported that Neoconocephalus retusus females chew through grass sheathes about 2 cm above ground level and push the ovipositor down into the sheath through the opening. The ovipositors of Belocephalus species are stouter than those of other genera, but no one has observed their use.

Remarks

Except among short-winged coneheads (Belocephalus), female coneheads are generally much larger than males. In a few species the smallest female known exceeds the largest male. The significance of such discrepant sizes is unexplained.

Coneheads are often easy to find at night by going to calls of males and by inspecting seed heads of grasses for feeding females. Some species fly to lights. Finding coneheads in the daytime is difficult. In at least two genera (Neoconocephalus and Pyrgocorypha) adults crawl head down in bunches of grass until only their wings and extended hindlegs are visible. In this posture the insect resembles just another green or brown grass blade.

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Creative Commons Attribution 3.0 (CC BY 3.0)

© Thomas J. Walker

Source: Singing Insects of North America

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