1. Trang chủ
  2. » Thể loại khác

Encyclopedia of biodiversity encyclopedia of biodiversity, (7 volume set) ( PDFDrive ) 2312

1 2 0

Đang tải... (xem toàn văn)

THÔNG TIN TÀI LIỆU

Thông tin cơ bản

Định dạng
Số trang 1
Dung lượng 53,8 KB

Nội dung

Grasshoppers and their Relatives distributed worldwide All species of the family spend their lives in underground tunnels, excavated with their extremely modified, shovel-like front legs The head is prognathous and somewhat elongated, and so is the pronotum The antennae are short and somewhat thickened, an apparent adaptation for their subterranean lifestyle The wings are usually fully developed, rarely absent The stridulatory apparatus of males is simple, lacking the mirror The females’ tegminal venation resembles that of the males, but lacks proper stridulatory organs Cerci in both sexes are long and flexible, acting as an extra pair of antennae while the insects are moving backward in their underground corridors Females lack an external ovipositor Mole crickets emerge from their tunnels only during courtship, although calling takes place underground To broadcast their signals as far as possible, males build Y-shaped tunnels, the length and diameter of which are perfectly suited to amplify the dominant frequencies of their call Females stridulate as well, but their call seems to have a territorial rather than a courtship role Eggs are often laid in special brooding chambers and actively cared for by the female Newly hatched nymphs stay in the chamber for a few weeks, feeding on humus and tender rootlets protruding into the burrow Several species of mole crickets are serious crop pests, not only because they feed on roots of plants but also because they damage entire root systems while digging tunnels A species of Gryllotalpa recently introduced accidentally to Australia has quickly become one of the major threats to the Australian golfing industry by damaging carefully manicured putting greens Gryllidae (True Crickets and Tree Crickets) The family Gryllidae is the largest lineage of the superfamily, with nearly 4700 species, assigned to nearly 600 genera in 21 subfamilies (there are several alternative systems of classification of crickets, and the number and status of higher categories varies among different authors) The body size of true crickets ranges from small (less than mm) to large (approximately 50 mm) Most members of the family are rather stout insects, with short, thick legs Phalangopsinae are a notable exception, having extremely long and slender legs and other appendages, making them resemble large spiders rather than typical crickets Delicate bodies with slender legs also characterize most tree crickets (Oecanthinae) The head is generally globular, except in tree crickets, which have an elongated, prognathous head The pronotum is generally quadrate The wings and stridulatory apparatus may be fully developed, reduced, or totally absent The fully winged forms often lack the stridulatory apparatus, whereas forms with greatly reduced tegmina can have a fully developed stridulatory apparatus Species with well-developed stridulatory apparatus usually produce melodious, frequency- and timemodulated calls, and many species have been kept as singing pets in Asia and Europe for many centuries Rarely, the call is short and clicklike (Eneoptera) Courtship behavior is often complex and involves acoustic, tactile, and olfactory signals The courtship song, produced only in the close proximity of the female, is quieter and of a different structure than the advertisement call It is usually produced by rubbing only a 729 part of the stridulatory file against the scraper Some spider crickets (Phalangopsinae) additionally drum with their legs During copulation, males produce spermatophores, which in some species contain a large spermatophylax Males of some species allow the female to feed on different parts of their bodies Males of tree crickets have thoracic glands, which the female licks during copulation, and females of some pygmy field crickets (Nemobiinae) feed on males tibial spines during copulation The ovipositor in true crickets is usually long, needlelike, sometimes laterally flattened, and swordlike (Trigonidiinae) or reduced (Brachytrupes) Opposition takes place in soil or plant tissues Maternal care is rare but sometimes quite well developed Females of Anurogryllus muticus excavate extensive subterranean burrows as a nursery for their eggs, which are aggressively protected against all intruders Newly hatched nymphs stay with their mother, who feeds them with unfertilized eggs, produced by her for the sole purpose of feeding her nymphs Major Subfamilies Gryllinae This subfamily includes the true crickets, placed in more than 1100 species and more than 100 genera They are distributed worldwide, and a few species closely associated with human habitats are virtually cosmopolitan Morphologically, Gryllinae are rather uniform, having stocky bodies, with a globular head and thick legs Most have welldeveloped wings and a stridulatory apparatus True crickets are some of the first singing insects to be heard in the spring in the temperate areas of Europe and North America, as they often overwinter as late-instar nymphs and mature as soon as the temperature allows them to become active North America has a particularly interesting fauna of true crickets, with several complexes of morphologically nearly identical, so-called ‘‘cryptic species.’’ Some of the species appear to be chronospecies, that is, very closely related species that avoid hybridization by being sexually mature during different times of the year Most true crickets are ground dwellers and many are territorial, vigorously defending their burrows In some species, a certain percentage of the males (satellite males) consistently exhibit a kind of sexual parasitism by intercepting females attracted to the call of another male Several species form large swarms, and some (e.g., Gryllus bimaculatus in Africa) can become serious agricultural pests The house cricket (Acheta domesticus) is a cosmopolitan insect associated with human dwellings and when occurring in large numbers can cause damage to stored food and other material Brachytrupinae This subfamily, often treated as a subset of the true crickets, includes about 20 genera and more than 220 species distributed mostly in the tropical and subtropical regions of the Old World, with relatively few species in the New World The wings in some species are greatly reduced or absent, and the female’s ovipositor is reduced Some of these crickets are very large and produce calls of an intensity directly proportional to their size Some species are gregarious and live in small underground colonies consisting of adults and nymphs of different ages Some species of the

Ngày đăng: 28/10/2022, 11:14