INVERTEBRATE ZOOLOGY IN THREE VOLUMES - BOOK 2 - H.Y. Shcherbak - 1996

PHYLUM ARTHROPODA

SUBPHYLUM CHELICERATA

CLASS ARACHNIDA

SUBCLASS SCORPIONS (SCORPIONES)

Class="center">

Scorpions are inhabitants of hot and warm Regions of the globe, lying approximately between the 50th parallels of northern and southern latitude; some species have been found in mountains at altitudes of 3–4 thousand meters above sea level. About 700 species have been described. In Ukraine, these animals are known in Crimea, where the Crimean scorpion (Euscorpius tauricus) is quite common. In addition, E. carpaticus is found in Transcarpathia (see Fig. 189, a), and Buthus caucasicus fischeri has been found near Odesa.

Fig. 198. Buthus eupeus (dorsal (a) and ventral (b) views):

1 - pedipalp chela; 2 - chelicera; 3 - prosoma (cephalothorax); 4 - mesosoma (preabdomen); 5 - metasoma (postabdomen); 6 - telson; 7 - venom sting; 8 - walking legs; 9 - genital opercula; 10 - pectines; 11 - stigma; 12 - anus

The size of scorpions ranges from 5 to 10 cm, with some reaching up to 18 cm, such as the African emperor scorpion (Pandinus imperator).

The external Morphology of scorpions is characterized most prominently by large pedipalps ending in chelae (claws), and the division of the body into three parts: the prosoma, mesosoma, and metasoma (Fig. 198). The chelicerae are small and chelate. The prosoma is covered by a single carapace; on the mesosoma, the segments have separate dorsal (tergites) and ventral (sternites) sclerotized plates. The genital opercula are located on the first segment of the mesosoma, while pectinate appendages—unique Organs found only in scorpions—are situated on the second segment. These bear sensilla of various structures. The exact function of these organs is not yet fully understood; it is quite likely that they serve as olfactory and tactile organs. Pulmonary stigmata, appearing as transverse slits, are located on the four subsequent segments.

The segments of the metasoma are surrounded by sclerotized rings and lack appendages. The metasoma terminates in a thickened caudal segment (telson), which houses the venom gland that opens via a duct at the tip of the sharp, curved sting.

The prosomal carapace bears a pair of rather large median eyes and up to five pairs of small lateral eyes. The coxae of the pedipalps and the first two pairs of walking legs feature masticatory processes (gnathobases) directed toward the Mouth.

Scorpions are nocturnal predators: by day they hide under rocks, in sand, beneath tree bark, etc., and emerge at night to hunt. While hunting, scorpions move slowly with their metasoma raised and semi-flexed pedipalps extended forward. These bear sensory hairs (trichobothria), thanks to which the scorpion reacts very sensitively to the Touch of moving objects. Prey is seized by the pedipalp chelae (the inner edges of both fingers of the chela are armed with strong Teeth) and immediately transferred to the chelicerae. Moving the chelicerae alternately, the scorpion tears its prey apart

and grinds it into a slurry-like mass, after which it sucks it out. If the prey begins to resist, the scorpion stings it several times before tearing it apart.

Scorpions feed exclusively on live prey, including insects, their larvae, spiders, and centipedes. There are known cases of scorpions consuming small lizards and even mice.

Most scorpions are viviparous, while some lay eggs from which young scorpions quickly hatch. Copulation is preceded by a "courtship dance". The male and female lock pedipalp chelae, raise their metasomas, and move together in a pair for many hours. Having found a suitable shelter, the male clears it using his caudal sting and legs, and deposits a spermatophore onto the substrate. He then pulls the female over it so that her genital aperture is positioned directly above the spermatophore. The female releases herself from the male, opens her genital opercula, grasps the spermatophore with them, and squeezes the sperm into her genital aperture.

The Development of fertilized eggs within the maternal body lasts from several months to a year. The embryos are nourished by secretions from specialized glandular appendages of the Ovary.

Young scorpions are born within an embryonic membrane, which they quickly shed. In many species, the female carries the newborn scorpions on her back for some time. At first, the scorpions do not feed, and only after their first molt do they leave the female's body and begin active hunting. They reach adulthood in a year and a half, after seven molts.

For the small animals upon which scorpions prey, their venom is lethal and acts quite quickly. For humans, a scorpion sting is not fatal, and the symptoms of envenomation subside within 2–3 days. However, cases involving severe and even fatal consequences from the stings of large scorpions are known.