Schizomida

Schizomida are a specialized order of arachnids. They are commonly known as sprickets or short-tailed whip-scorpions. These small, soft-bodied creatures are part of a group that scientists are still working hard to understand. The famous biologist E. O. Wilson noted that schizomids are among the organisms that desperately need more experts to study them. Currently, about 300 species have been described across the globe. Most of these species belong to the family Hubbardiidae.

The anatomy of a schizomid is quite unique. Their body is divided into two main sections. The front section is the prosoma, or cephalothorax. The name Schizomida means "split or cleaved middle." This refers to how the prosoma is divided into two separate plates. These plates include a large protopeltidium and smaller, paired mesopeltidia and metapeltidia. Behind the prosoma is the opisthosoma, which is the abdomen. The opisthosoma is a smooth oval made of 12 recognizable segments. The first segment is reduced to form a structure called the pedicel. The last three segments are constricted to form the pygidium. At the very end, they possess a short, whip-like tail called a flagellum. This flagellum has no more than four segments. In males, the flagellum is only a single segment. Females generally have flagella with three or four segments.

Schizomids have highly modified limbs for survival. Although they are arachnids, they only use six legs for walking. They have modified their first two pairs of legs into sensory organs. These are often called antenniform legs. They use these legs to feel their surroundings and find prey. Just behind these sensory legs, they have large, well-developed pedipalps. These act like pincers to seize victims. Their hind legs are also specialized for jumping. This allows them to perform an escape response if they are threatened. Interestingly, schizomids do not have true eyes. Some species possess vestigial eyespots. These simple structures can only distinguish between light and dark. They breathe using a single pair of book lungs. These lungs are located on the second abdominal segment.

The evolutionary history of these animals is very deep. Schizomids are the sister group to the order Uropygi. Together, these two groups form the clade known as Thelyphonida. Molecular clock data suggests both orders likely originated during the late Carboniferous period. This was in the tropical regions of the supercontinent Pangea. Schizomids underwent a period of substantial diversification during the Cretaceous period. The oldest known fossils of this group come from Mid-Cretaceous Burmese amber in Myanmar. These ancient fossils can be assigned to the Hubbardiidae family.

Schizomids are found in many tropical and subtropical habitats globally. They live in Southeast Asia, India, Australia, and several Pacific Islands. They are also found in Central and South America and Africa. Some populations exist in temperate areas like Texas and California. The Hubbardiidae family has a global distribution. However, the Protoschizomidae family is only found in Mexico and Texas. While not native to Europe, they have been introduced to countries like Britain, France, the Czech Republic, and Poland. In these places, they live only in artificial greenhouse environments. Most species have very restricted distributions and are only known from one specific location.

Maintaining high humidity is vital for their survival. They must avoid desiccation, which is the process of drying out. You can find them in rainforest leaf litter or organic soil. They also hide under rocks, in rotten logs, or inside caves. Some species have adapted to live in insect nests. For example, *Afrozomus machadoi* lives in termite mounds. *Stenochrus portoricensis* has been found in ant colonies. In South America, *Surazomus arboreus* lives in trees to avoid drowning during seasonal floods. Some species can even survive in cold environments. In California, certain *Hubbardia* species live under snow-covered rocks. *Hubbardia briggsi* is often found in snowy habitats during the winter.

As active predators, schizomids play a role in their ecosystems. They use their antenniform legs to search the soil for invertebrates. Their diet includes isopods, millipedes, cockroaches, worms, and springtails. They even eat termites, booklice, and other schizomids. They can hunt prey that is as small as 10% of their body or as large as 100%. Once they find a target, they lunge and seize it with their pedipalps. They may carry the prey to a crevice to eat it. They use chelicerae to dismember the prey. Then, they turn the tissues into a liquid called chyme. They ingest this liquid through suction. Some species, like *Hubbardia pentapeltis*, are very hardy and can survive five months without food.