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What is a Katydid?
Insecta, Orthoptera, Ensifera, Tettigoniidae
Figure 1: External Body Morphology of a Katydid
Introduction:
Katydids (Tettigoniidae) are one of the most common members of tropical insect
communities, whose distribution range from the littoral zone of the shoreline, to the
various life zones of tropical rainforests. Presently, Tettigoniidae contains more than
1000 genera with over 6400 described species (Naskrecki and Otte, 1999). Katydids are
found on all continents except Antarctica, majorities of which are found in the tropics;
there are around 255 species in North America. Most katydids are nocturnal, foraging and
mating during the night, while finding a roosting spot early in the day before diurnal
predators become active (Gwynne, 2001)(Castner and Nickle, 1995c). Katydids are in the
order Orthoptera, which means “straight-winged”, other members of this order include
grasshoppers, crickets, and mole crickets. Katydids can be distinguished from these other
insect families by the elongation of their antennae, which can exceed three times the
length of their body. Numerous species of Katydids are model organisms for insect
defense, due to their leaf-mimicking adaptation (Castner and Nickle, 1995a). Most
katydids are herbivorous, consuming leaves, stems and in some cases vegetative detritus.
Some katydids if they reach large enough size are carnivorous, feeding on other insects,
gastropods and sometimes vertebrates.
Communication:
Male katydids produce sound through a process called stridulation, in which they rub the
edges of their front wings together in order to attract females over long distances. One
side of the wing has abrasive ridges called the file, while the other wing has rasp-like
structures that produce the sound, the plectrum (Fig 1.). Not only do most orthopterans
have the ability to produce sound, they can also hear. The hearing organs (tympanum) of
katydids are located on their front legs (tibia) (Fig. 2). The songs of katydids are species
specific, and have been used to construct phylogenetic relatedness among different
katydid clades (Naskrecki 2000). The earliest evidence of stridulation has been found in
fossilized Katydids from the Jurassic (165 mya) (Sismondo 1990).
Figure 1: Stridulatory organs on the forewing.
The file and scraper (plectrum) are rubbed
together producing a chirping sound.
Figure 2: Katydid Foreleg. Note the tympanum at
the top of the Tibia.
Reproduction:
Katydids are further ranked into the suborder Ensifera which translates to “sword bearer”,
referring to the elongated sword-like ovipositor that females use to lay eggs into dead
leaves or stems (Fig. 3). The shape of female ovipositors is highly diverse, with different
morphologies adapted to laying eggs onto different substrates. Sickle-shaped ovipositors
lay eggs in living plant matter such as leaves, while straight ovipositors lay eggs in grass
stems (Gwynne 2001). The ovipositor consists of three appendages to assist in first laying
the egg, manipulating the substrate, and placing it properly. Males also provide a nuptial
gift to females in the form of a spermatophylax, which is a highly nutritious gelatinous
food source for females to consume during copulation (Fig. 4). The function of the
nuptial gift is to increase the time of copulation to ensure successful paternity.
Differential success among males is dependent on the intensity of male competition, and
resource abundance in order to invest enough energy for a substantial nuptial gift
(Gwynne et al. 1994).
Figure 3: Elongated sword-like ovipositor
on a female.
Figure 4: A nuptial gift (Spermatophylax) adhered
to the abdomen of a female.
Life Cycle:
Most katydids live for around a year, and mating season is during the late summer.
Females lay their eggs in rows on their preferred host plant; eggs are oval in shape.
Katydids are paurometabolous (incomplete metamorphosis) in which juvenile molts
(instars) look like miniature versions of adults, and do not acquire reproductive ability or
wings until the final molt (Capinera et al. 2004). In some species the instars do not
resemble the adults, but mimic other species such as spiders or flowers in order to deter
predation.
Leaf Mimicry:
Research has shown that katydids are more highly preyed on when their roosting
substrate contrasts with their own body color, which may account for why they have
strong selective forces to resemble leaves (Evans and Schmidt, 1990). Such mimicry can
be extremely detailed, in which body forms can exhibit sticks or stems, lichen or fungal
spots, rocks, leaf-venation, generalized color matching, or various combinations (Hogue
1993)(Gwynne 2001)(Fig 5). Some Katydids, especially in the genus Pterochrozini have
adapted highly detailed elaborations on their wings to enhance their leaf mimicry such as
blotches of discoloration or transparent membranes to imitate leaf decay and herbivory
respectively (Caster and Nickle 1995c). Due to predator search images, seasonality,
spatial variations of background vegetation, and conspecific density, certain tribes of
katydids display phenotypic plasticity, in which one species can produce a variety of
color morphs to imitate the different colors of dead and live vegetation (Lymbery
1992)(Gwynne 2001). Furthermore, due to seasonality in the neotropics, more dead
foliage appears in the dry season, in which katydids shift from green color morphs to
predominantly brown color morphs (Lymbery 1992)(Gwynne 2001).
Figure 5: The genus Pterochrozini display a wide diversity of leaf-mimicking capabilities ranging in color
and form. Note the blotches of discoloration (bottom left) and transparent membranes (top left).
Works Cited:
• Castner, J.L., and D.A. Nickle. 1995a. Intraspecific Color Polymorphism in LeafMimicking Katydids (Orthoptera: Tettigoniidae: Pseudophyllinae: Pterochrozini)
Journal of Orthoptera Research 4: 99-103
• Castner, J.L., and D.A. Nickle. 1995c. Observations of the Biology and Behavior
of Leaf-Mimicking Katydids (Orthoptera: Tettigoniidae: Pseudophyllinae:
Pterochrozini) Journal of Orthoptera Research 4: 93-97
• “Chapter 4 Classes of Arthropod Pests of the Urban Community.” Urban
Entomology (Ebeling Chap. 4) Classes of Arthropod Pests of the Urban
Community. N.p., n.d. Web. 19 Apr. 2015.
• Capinera, John L., Ralph D. Scott, and Thomas J. Walker. Field guide to
grasshoppers, katydids, and crickets of the United States. Ithaca, NY: Cornell
University Press, 2004.
• Evans, D.L., and J.O. Schmidt. 1990. Insect Defenses: Adaptive mechanisms and
strategies of prey and predators. State University of New York, Albany. Press.
• Gwynne, Darryl T., and William D. Brown. "Mate feeding, offspring investment,
and sexual differences in katydids (Orthoptera: Tettigoniidae)." Behavioral
Ecology 5.3 (1994): 267-272.
• Gwynne, Darryl T. Katydids and Bush-Crickets Reproduce Behavior and
Evolution of the tettigoniidae. Ithica: Cornell university press. 2001. Print.
• Hogue, C.L. 1993. Latin American Insects and Entomology. University of
California Press, Berkeley and Los Angeles: 156
• Lymbery, A. J. 1992. The environmental control of colouration in a bushcricket,
Mygalopsis marki Bailey (Orthoptera: Tettigoniidae). Biol J. Linn. Soc. 45: 7189.
• Naskrecki, Piotr. "The phylogeny of katydids (Insecta: Orthoptera: Tettigoniidae)
and the evolution of their acoustic behavior." (2000).
• Naskrecki, P. and D. Otte. 1999. An illustrated catalog of Orthoptera. Vol. I.
Tettigonioidea (CDROM). The Orthopterists’ Society at the Academy of Natural
Sciences of Philadelphia, Publications on Orthopteran Diversity.
• Sismondo, Enrico. "Synchronous, alternating, and phase-locked stridulation by a
tropical katydid." Science 249.4964 (1990): 55-58.