Most grasshoppers feed and mate during the day but molt and lay their eggs at night. The majority of katydids and crickets tend to be active at night, especially in the tropics. However, a wasp-mimicking katydid from Central America is active during the day. These katydids are black and orange and strongly resemble the large tarantula hawk wasps. These harmless katydids not only look like wasps, they act like them too. They are found in sunny openings in lowland rainforests, where they move in a jerky, wasplike fashion, constantly twitching their orange-tipped antennae. At night their behavior changes. Unable to rely on their wasplike appearance to fool their enemies in the dark, their movements become slow and deliberate, just like the katydids that resemble leaves.
Most orthopterans tend to live by themselves, except during the mating season. However, many crickets are often found in small groups. Locusts sometimes form massive swarms made up of hundreds of thousands, even billions, of individuals. Locusts are grasshoppers that show a definite change in their behavior, shape, and vital body functions as they go from living alone to joining other individuals in swarms. Other groups of orthopterans also form swarms. The North American Mormon cricket is actually a large, wingless katydid that regularly forms large groups that can totally destroy any crops in their paths. African conehead katydids also form large flying swarms.
One of the most common features associated with many or-thopterans is their ability to produce sounds. There are few places during the warmer months where the daytime rasps and snaps of grasshoppers or the nocturnal chirps, clicks, and buzzes of katydids and crickets cannot be heard. These calls are produced to claim territory, attract mates, or to sound an alarm. The volume and pitch of the calls, usually produced by males, are unique to each species and helps them to recognize one another.
Contrary to popular belief, none of these insects produces sounds by rubbing its legs together. Males produce sounds by rubbing the bases of their wings together or their hind legs against the edges of the wings. Crickets and katydids generally rub a set of tiny pegs, or file, located at the base of one wing against a strong ridge, or scraper, on the other wing to produce buzzes, chirps, and clicks. A few species grind their jaws together to produce sounds, while others rub the bases of their legs against the underside of the thorax. The sound produced is amplified by a smooth membrane located on the base of the wings.
Grasshoppers "sing" by rubbing the inside surface of their jumping legs against the edges of their forewings. They can amplify the sound by expanding their wings. Some grasshoppers also make a crackling sound when they fly. The sound is produced by rapidly bending their hind wings while in the air. The crackling sound is common among band-winged grasshoppers and is used in courtship and territorial displays.
Courtship and mating behaviors involve sight, sound, smell, and touch. Grasshoppers use mostly visual communication. Males often have bright markings on different parts of their bodies and wings that are unique to their species. They instinctively display these features as if they were in a highly practiced dance routine. Male crickets and katydids sometimes produce two different kinds of calls. The first is used as longrange advertising to attract a female. The second is quieter and is used in courtship when the female is nearby. In a few species, the females may respond with a call of their own. Courtship in katydids and crickets depends not only on sounds but also on smells. Odors, or chemical signals, make sense since they are mostly active at night and cannot see each other, but their use of smells is not very well known. A few species, such as female giant wetas in New Zealand, produce pheromones (FEH-re-moans) and other odors to attract males.
Males place the sperm packet directly into the body of the female. The sperm packet may weigh as much as 60% of the total body weight of the male. In some species the males have special organs that are eaten by the female while they are mating. In other species males have special projections on their abdomens that are used to hold the female while they mate.
Most female crickets and katydids use their hooked, needlelike, or swordlike ovipositors to place eggs out of harm's way deep into soil or rotting wood. Female grasshoppers lack external ovipositors, but have thickened valves on the tips of their abdomen. They drill through the soil using hardened plates on the tip of their abdomens and deposit them deep in the soil or rotten wood by stretching the entire length of their abdomen into the hole. Sometimes the eggs are placed in a foamy mass that helps to keep them from drying out.
The larvae usually hatch within a few weeks or months, sometimes longer. They strongly resemble the adults when they hatch but lack developed wings and reproductive organs. Most orthopterans do not care for their young, although in some species the mother will guard her eggs. Mole crickets lay their eggs in special chambers and lick them to prevent them from becoming spoiled by fungus. After hatching, the young mole cricket larvae remain with their mother for a few weeks before going out on their own. Larvae develop gradually, molting six to ten times before reaching adulthood.
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