Key to Australian Freshwater and Terrestrial Invertebrates

Phylum Arthropoda
Subphylum Chelicerata
Class Arachnida
Order Schizomida

Common names: schizomids, micro-whip scorpions

Overview

Schizomids are small arachnids, usually less than 10 mm in length. They are easily recognisable by the presence of very long first pair of legs, short flagellum and divided sternum. The very elongate first pair of legs are used like antennae, and actively tap and explore the environment in front of the animal. The posterior legs are usually slightly enlarged with large femora. Schizomids are capable of very fast movement over short distances, both backwards and forwards. The pedipalps are thickened, raptorial and do not possess many enlarged spines. The pedipalps function in a vertical (up-and-down) fashion, differing from most other arachnids in which prey-capturing pedipalps operate horizontally and in opposition. Schizomids lack a medial body constriction and the abdomen terminates in a short tail-like structure (flagellum) that is composed of three to four slender segments in females, but of a single, often bulbous, segment in males. The flagellum of males has complex morphology and is often used to distinguish species.

Distribution and diversity

Schizomids have a coastal, topical and subtropical distribution in Australia. They are one of the smaller arachnid orders with around 270 species worldwide and more than 50 described species from seven genera in a single family from Australia. However, numerous unnamed species are known and the true size of the fauna is estimated to be greater than 100 species.

Life cycle

Mating in schizomids is unique in that the flagellum plays an essential role. The male taps the female with his first pair of legs then turns around and presents his flagellum to her. The female takes the flagellum into her chelicerae after which the male deposits a spermatophore (sperm packet) on the substratum. The male then moves backwards and the female follows, until she reaches the spermatophore and takes it into her gonopore (genital opening). Prior to laying several eggs, the female builds a small brood chamber in the soil. The eggs are guarded and remain attached to her abdomen. After hatching, the female and the juveniles emerge from the brood chamber and disperse, the juveniles moulting several times before becoming mature.

Feeding

All schizomids are predators and they capture small arthropods with their pedipalps. The pedipalps lack the spines characteristic of whip spiders, but are still used to hold prey. The chelicerae are used to chew through the exoskeleton into which digestive enzymes are passed and the pre-orally digested contents are sucked up.

Ecology

Schizomids are primarily tropical and are restricted to damp habitats such as leaf litter, under the bark of rotting logs or in caves. Their impact as predatory arachnids is poorly known and they are not economically significant.