Growth and life span
- Related Topics:
- ice bug
- phasmid
- Orthoptera
- Dictyoptera
- Exopterygota
The life span of orthopterans depends in part upon whether or not there are long periods during winter or at other times (e.g., a dry season) when the insects are quiescent. Some species habitually spend several months resting during unfavorable periods; such species have one generation per year, and the life span of an individual is approximately one year. The portion of the life span spent as an adult varies, but is likely to be about one or two months. In some species egg maturation is delayed several months after the final molt, and the females do not lay the eggs until they have matured. In other species eggs are not hatched until one or more years after they are laid; therefore, more than one winter or dry season is passed in the egg stage, and a single life cycle can occupy two or more full years.
Reproduction
General features
Typically each female has paired ovaries consisting of tubes in which eggs develop, moving posteriorly into a single oviduct as they “ripen.” The oviduct leads to a vagina and then to the exterior where there is either a simple or specialized ovipositor consisting of paired appendages called ovipositor valves. Attached to the oviduct or vagina is a sac (called the spermatheca) for storage of male sperm; as eggs move down the oviduct, they are fertilized by the sperm. The typical male contains paired testes that produce vast numbers of slender active sperm; these are stored in enlargements of the tubes leading posteriorly from the testes. Accessory gland secretions provide not only the medium for carrying the sperm but also a material that solidifies to form a thin-walled sac, or reservoir, containing some sperm and fluid. This reservoir, called the spermatophore, is almost universally found among orthopterans.
Grasshopper spermatophores consist of a bladderlike reservoir and a spermatophore tube. The spermatophore is formed during the first two minutes or so of copulation, after which the tube extends from the male genital organs to the spermathecal duct of the female. The spermathecal duct opens at the base of the ovipositor valves. Sperm pass to the female during copulation; after sperm transfer is complete, parts of the spermatophore may remain attached to both male and female. In some orthopterans, particularly crickets and katydids, the entire spermatophore is attached to the female.
Courtship behavior
All orthopteran groups have species that show definite courtship behavior prior to actual mating. Among the grasshoppers, species with colored hind wings and the habit of making sounds during flight use hovering and other special flight patterns to attract the attention of females. Crickets and katydids have the most dramatic courtship displays because “songs” enter into the precopulatory behavior. Females of some species are receptive only to the specific song of a male of the same species; in others, however, mating calls are not necessary, and a female will mate with a male who is unable to sing because his wings have been removed. Here, as in grasshoppers, a variety of mating positions are assumed.