Tettigoniidae

"Katydid" redirects here. For other uses, see Katydid (disambiguation).
Tettigoniidae
Temporal range: Jurassic–recent
Male katydid, Scudderia sp.[1]
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Orthoptera
Suborder: Ensifera
Infraorder: Tettigoniidea
Superfamily: Tettigonioidea
Krauss, 1902
Family: Tettigoniidae
Krauss, 1902
Subfamilies

See text

Grey bush-cricket (Platycleis albopunctata) male

Insects in the family Tettigoniidae are commonly called katydids or bush crickets. More than 6,400 species are known. Part of the suborder Ensifera, Tettigoniidae is the only family in the superfamily Tettigonioidea.

Primarily nocturnal in habit, with strident mating calls, many katydids exhibit mimicry and camouflage, commonly with shapes and colors similar to leaves.[2]

Etymology

The scientific name "Tettigoniidae" is derived from the genus Tettigonia, first described by Carl Linnaeus in 1748. Latin tettigonia means leafhopper; it is from Greek tettigonion, the diminutive of the imitative (onomatopoeic) τέττιξ, tettix, cicada.[3][lower-alpha 1]

The common name "katydid" is also onomatopoeic.[5]

Description and lifecycle

Description

Tettigoniids range in size from as small as 5 to as large as 130 mm.[6] The smaller species typically live in drier or more stressful habitats which may lead to their small size. The small size is associated with greater agility, faster development, and lower nutritional needs. Tettigoniids are tree-living insects that are most commonly heard at night during summer and early fall.[7] Tettigoniids may be distinguished from the grasshopper by the length of their filamentous antennae, which may exceed their own body length, while grasshoppers' antennae are always relatively short and thickened.

Lifecycle

The lifespan of a katydid is about a year, with full adulthood usually developing very late. Females most typically lay their eggs at the end of summer beneath the soil or in plant stem holes. The eggs are typically oval-shaped and laid in rows on the host plant. The way their ovipositor is formed relates to its functional adaptability in the areas which it lays eggs. The ovipositor is an organ used by insects for laying of eggs. It consists of a maximum of three pairs of appendages formed to transmit the egg, to prepare a place for it, and place it properly. Tettigoniids have either sickle-shaped ovipositors which typically lay eggs in dead or living plant matter, or uniform elongated ovipositors which lay eggs in grass stems. When tettigoniids hatch, the nymphs often look like smaller versions of the adults, but in some species, the nymphs look nothing at all like the adult and rather mimic other species such as spiders and assassin bugs, or flowers, to prevent predation. The nymphs remain in a mimic state only until they are large enough to escape predation. Once they complete their last molt, they are then prepared to mate.[7]

Distribution

Tettigoniids are found on every continent except Antarctica.[8] The vast majority of katydid species live in the tropical regions of the world.[2] For example, the Amazon basin rain forest is home to over 2000 species of katydids.[2] However, katydids are found in the cool, dry temperate regions, as well, with about 255 species in North America.

Bush cricket on a rock, San Felice Circeo, Italy

Ecology

The diet of tettigoniids includes leaves, flowers, bark, and seeds, but many species are exclusively predatory, feeding on other insects, snails, or even small vertebrates such as snakes and lizards. Some are also considered pests by commercial crop growers and are sprayed to limit growth, but population densities are usually low, so a large economic impact is rare.[9] By observing the head and mouthparts, where differences can be seen in relation to function, it is possible to determine what type of food the tettigoniids consume. Large tettigoniids can inflict a painful bite or pinch if handled, but seldom break the skin.

Some species of bush crickets are consumed by people, like the nsenene (Ruspolia baileyi) in Uganda and neighbouring areas.

Communication

The males of tettigoniids have sound-producing organs (via stridulation) located on the hind angles of their front wings. In some species, females are also capable of stridulation. Females chirp in response to the shrill of the males, which sound like, "katy did," which is how they received their name. The males use this sound for courtship, which occurs late in the summer.[10] The sound is produced by rubbing two parts of their bodies together, called stridulation. One is the file or comb that has tough ridges; the other is the plectrum is used to produce the vibration.[11] For tettigoniids, the fore wings are used to sing. Tettigoniids produce continuous songs known as trills. The size of the insect, the spacing of the ridges, and the width of the scraper all influence what sound is made.[12]

Many katydids stridulate at a tempo which is governed by ambient temperature, so that the number of chirps in a defined period of time can produce a fairly accurate temperature reading. For American katydids, the formula is generally given as the number of chirps in 15 seconds plus 37 to give the temperature in degrees Fahrenheit.

Predation

Some tettigoniids have spines on different parts of their bodies that work in different ways. Listroscelinae is an example of one that has limb spines on the ventral surface of their body. This works in a way to confine their prey to make a temporary cage above its mouthparts. The spines are articulated, comparatively flexible, but relatively blunt. Due to this they are used to cage and not penetrate the prey’s body. Spines on the tibiae and the femora are usually more sharp and nonarticulated. They are designed more for penetration or help in the defensive mechanism they might have. This will usually work with their diurnal roosting posture to maximize defense and prevent predators from going for their head.[13]

Defense mechanisms

When tettigoniids go to rest during the day, they go into a diurnal roosting posture to maximize its cryptic qualities. This position fools predators into thinking the katydid is either dead or just a leaf on the plant. Various tettigoniids have bright coloration and black apical spot on the inner surface of the tegmina, and brightly colored hind wings. By flicking their wings open when disturbed they use the coloration to fool predators into thinking the spots are eyes. This in combination with their coloration mimicking leaves allows them to blend in with their surroundings, but also makes predators unsure which side is the front and which side is the back.[14]

Reproductive behavior

The males provide a nuptial gift for the females in the form of a spermatophylax, a body attached to the males' spermatophore and consumed by the female. The function of the spermatophylax is to increase the attachment time of the male's spermatophore and thereby increase his paternity.[15]

Polygamy

Tettigoniidae have a polygamous relationship with one another. The first male to mate is guaranteed an extremely high confidence of paternity when a second male couples at the termination of female sexual refractoriness. This investment functions are a parental paternity. The nutrients the offspring will ultimately receive will increase the fitness. The second male to mate with the female at the termination of her refractory period is usually cuckolded.[16]

Competition

The polygamous relationships of the Tettigoniidae lead to high levels of male-male competition. Male competition in the Tettigoniidae species is caused by the decreased availability of males able to supply nutritious spermatophores to the females. Females will produce more eggs on a high-quality diet; thus, the female looks for healthier males with a more nutritious spermatophore. Females will use the sound created by the male to judge the fitness of the male. The louder and more fluent the trill, the higher the fitness of the male.[17]

Stress response

Oftentimes in species which produce larger food gifts, the female is the individual that seeks out the males in order to copulate. This however is a cost to females as they risk predation while searching for males. There is also a cost-benefit tradeoff in the size of the spermatophore which the male Tettigoniidaes produces. When male Tettigoniidae possess a large spermatophore they benefit by being more highly selected for by females, however they are only able to mate one to two times during their lifetime. Inversely, male Tettigoniidae with smaller spermatophores have the benefit of being able to mate two to three times per night, but have lower chances of being selected for by females. Even in times of nutritional stress, male Tettigoniidae will continue to make invest nutrients within their spermatophore. In some species the cost of creating the spermatophore is low, but even in those which it is not low, it is still not beneficial to reduce the quality of the spermatophore as it would lead to lower reproductive selection and success. This low reproductive success is attributed to some Tettigoniidae species in which the spermatophylax that the female receives as a food gift from the male during copulation increase the reproductive output of the reproduction attempt. However, in other cases, the female receives few if any benefits.[18]

The reproductive behavior of bush crickets has been studied in great depth. Studies conducted in 2010 at the University of Derby by Karim Vahed, Darren Parker and James Gilbert found that the Tuberous Bushcricket (Platycleis affinis) has the largest testes in proportion to body mass of any animal recorded. They account for 14% of the insect's body mass and are thought to enable a fast re-mating rate.[19]

The males provide a nuptial gift for the females in the form of a spermatophylax, a body attached to the males' spermatophore and consumed by the female. The function of the spermatophylax is to increase the attachment time of the male's spermatophore and thereby increase his paternity.[15]

Classification

Tettigoniidae is a large family and has been divided into a number of subfamilies:

Notes

  1. ↑ All of these names such as tettix with repeated sounds are onomatopoeic, imitating the stridulation of these insects.[4]

References

  1. ↑ Cirrus Digital: Bush Katydid Scudderia sp.
  2. 1 2 3 Ediotrs of Encyclopaedia Brittanice & others. "Katydid". Encyclopaedia Brittanica Online. Retrieved 9 October 2014.
  3. ↑ "Tettigoniidae". Merriam-Webster. Retrieved 31 March 2015.
  4. ↑ "Tettix". Merriam-Webster. Retrieved 31 March 2015.
  5. ↑ Harper, Douglas. "katydid". Online Etymology Dictionary.
  6. ↑ Funk & Wagnalls New World Encyclopedia (1 ed.). EBSCO Publishing. p. 1.
  7. 1 2 Rentz, David (15 July 2010). "A guide to the katydids of Australia". Journal of Insect Conservation. 14 (6): 579–580. doi:10.1007/s10841-010-9312-4.
  8. ↑ "Bush crickets". BBC Nature. Retrieved 25 November 2013.
  9. ↑ "Tree of Life project". Retrieved 25 November 2013.
  10. ↑ Columbia Electronic Encyclopedia (6 ed.). p. 1. Retrieved 10 December 2014.
  11. ↑ Robertson, Laura; Meyer, John (January 2010). "Exploring Sound with Insects". Science Scope. 33 (5): 12. Retrieved 10 December 2014.
  12. ↑ Chapman, R.F. The Insects: Structure and function (5 ed.). Cambridge University Press. ISBN 978-0521113892.
  13. ↑ Montealegre, Fernando; Morris, Glenn (24 Dec 2003). "The spiny devil katydids, Panacanthus Walker (Orthoptera: Tettigoniidae): an evolutionary study of acoustic behaviour and morphological traits". Systematic Entomology. 29 (1): 29–57. doi:10.1111/j.1365-3113.2004.00223.x.
  14. ↑ Castner, James; Nickle, David (Aug 2004). "Notes on the biology and ecology of the leaf-mimicking katydid Typophyllum bolivari Vignon (Orthoptera: Tettigoniidae: Pseudophyllinae: Pterochrozini)". Journal of Orthoptera Research. 4: 105–109.
  15. 1 2 Vahed, Karim (1998). "The function of nuptial feeding in insects: A review of empirical studies". Biological Reviews. Cambridge Philosophical Society. 73 (1): 43–78. doi:10.1111/j.1469-185X.1997.tb00025.x.
  16. ↑ Gwynne, G.T. (December 1988). "Courtship feeding in katydids benefits the mating male's offspring". Behavioral Ecology and Sociobiology. 23 (6): 373–377. doi:10.1007/bf00303711.
  17. ↑ Gwynne, Darryl T.; Brown, William D. (1994). "Mate feeding, offspring investment, and sexual differences in katydids (Orthoptera: Tettigoniidae)". Behavioral Ecology. 5 (3): 267–272. doi:10.1093/beheco/5.3.267.
  18. ↑ Jia, Zhiyun; Jiang, Zhigang; Sakaluk, Scott (2000). "Nutritional condition influences investment by male katydids in nuptial food gifts". Ecological Entomology. 25 (1): 115–118. doi:10.1046/j.1365-2311.2000.00239.x.
  19. ↑ Vahed, K.; Parker, D. J.; Gilbert, J. D. J. (2010). "Larger testes are associated with a higher level of polyandry, but a smaller ejaculate volume, across bushcricket species (Tettigoniidae)". Biology Letters. 7 (2): 261–4. doi:10.1098/rsbl.2010.0840. PMC 3061181Freely accessible. PMID 21068028.
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