Arachnids: spiders and scorpions of Lebanon
Arachnids (Class: Arachnida)
Arachnids are a class of arthropods, a phylum that also includes insects and crustaceans. Their body is made up of two parts, the rear abdomen, and the front cephalothorax to which eight legs are attached (with some exceptions), while adult insects all have a body made up of three parts and possess six legs.
Besides the eight legs, arachnids have an extra pair of “specialized” appendages located at the frontmost of the cephalothorax close to the mouth called Pedipalps. Their morphology and functions differ from one group of arachnids to another. For example, in spiders they are mainly sensory; in scorpions and pseudoscorpions, the pedipals end with pincers (claws) used for defense and prey holding; in harvestmen they are for hunting (raptorial). Most arachnids are carnivorous, like spiders and scorpions. Other kinds like ticks and mites are parasitic (suck blood and other body secretions of hosts).
Arachnids of Lebanon
Lebanon is home to thousands of species of arachnids most of which are understudied. The most popular species of arachnids are spiders (order Araneae) and scorpions (order Scorpiones), both of which are venomous. Other kinds of arachnids such as Camel Spiders (order Solifugae), False Scorpions(order Pseudoscopiones), Harvestmen (order Opiliones) as well as parasitic ones, like mites (super orders Parasitiformes and Acaratiformes), and ticks (order Ixodida), are all present in Lebanon.
Spiders (Araneae)
Spiders are the largest group of arachnids in Lebanon (and the world). They are generally characterized by having sensory hairs covering their body and pedipalps, chelicerae with fangs able to inject venom to digest their prey (sometimes defense), and spinnerets that secrete silk. Spiders are great pest control as they mainly feed of insects. Some larger species such as the Black Tarantula (Chaetopelma olivaceum) can also feed on lizards and baby rodents when the opportunity presents itself.
Mediterranean Black Tarantula (Chaetopelma olivaceum) is the most common tarantula in Lebanon. Like most old world tarantulas, the species is very defensive when threatened. A bite from this species is unpleasant but mild.
Different spider families evolved to use a vast variety of techniques for hunting prey.
Wolf spiders (Family: Lycocidae) for example, actively chase their prey; whereas Orb Weavers (Family: Araneidae) build a big sticky web to catch prey (ex. Argiope sp.) . They often choose places like garden or riversides rich in flying insects to build their webs.
Female Wolf Spiders are caring mothers. They carry their eggs sack until they hatch, then keep their newborn babies on their back until they molt and ready to hunt.
© Ramy Khashab
Crab Spiders (Thomisidae family) are mainly ambush predators that count on their camouflage to capture their preys, and almost never build webs. Species like the Flower Crab Spider (Thomisus sp.) are resident of flowering plants. They mainly target pollinators (bees, butterflies, flies, etc.) and are even able of changing their color to match the flower host they are hunting on.
Jumping Spiders (Salticidae) have great eyesight used to spot moving prey. Spider then slowly approach the prey and catch in one fast jump after securing itself with a single thread of silk (safety precaution).
Daddy Long-legs aka Cellar Spider (Pholcidae) is common residence in many houses and storage rooms where multiple spiders can be seen on one big web in the corners of the room.
Below are two other examples of spiders met in Lebanon.
Scorpions (Scorpiones)
Scorpions are easily recognizable arachnids with their pincers and a long, narrow, segmented tail with a sting at its end. Lebanon is home to more than 10 species of scorpions belonging to two families Scorpionidae and Buthidae.
Scorpionidae
Species of the Scorpionidae family generally have thick, powerful pincers used for subduing prey, and a thin tail that secretes venom of a relatively low toxicity. They are not dangerous for humans. The only confirmed species in Lebanon is one of the Burrowing Large-clawed Scorpions (Scorpio sp.), Scorpio fuscus, although more species of the same genus are probably present.
Buthidae
The Buthidae family, on the other hand, is the richest family of scorpions in Lebanon and in the world. Some species of this family are quite common such as Black Judaicus Scorpion (Hottentotta judaicus). Black Judaicus Scorpion is a common coastal scorpion species found in rocky habitats. It is distinguishable by its thin reddish pincers.
Scorpions such as the Deathstalker (Leiurus abdullahbayrami) and the Arabian Fat-tailed Scorpion (Andractonus crassicauda), are quite common in the semi-desert parts of Lebanon. Both species are considered some of the most venomous scorpions in the world. Although the Deathstalker is considered medically important, it is also responsible for most scorpion sting cases in Lebanon.
Compsobuthus sp. is a genus of dwarf scorpions that can be found in several different habitats throughout Lebanon which raises the possibility of more than one species being present.
© Ramy Khashab
Orthochirus innesi is a tiny species (2 cm) of thick-tailed scorpions found in the arid parts of northern Bekaa. It is recognizable thanks to its huge tail relatively to its total size. One can mix it with juveniles of the Arabian Fat-tailed Scorpion which is found in the same habitat.
© Ramy Khashab
False Scorpions (Pseudoscorpiones)
Pseudoscorpions are tiny arachnids most of which do not exceed 0.5 centimeters in size. Despite their size, they are easily recognizable by their segmented body and pedipalps with pincers making them appear like tailless scorpions. Pseudpscorpions seek shelter under tree bark, in rotten wood or cracked rocks, and occasionally inside human residence (dark humid storage room or cellar). Pseudoscorpions have a venom duct in the mobile finger of their pincers. The venom is used to neutralize their prey of smaller invertebrates and is completely harmless to humans. Pseudoscorpions are great pest eliminators as they feed on harmful species like mites and cloths moth larva. Many Pseudoscorpion species use bigger insects like beetles or flies as transportation to fly from one spot to another which is a great example of phoresy (a temporary commensalism for transportation).
Camel Spiders (Solifugae)
It is a group of non-venomous arachnids some of which can exceed 10 centimeters in length (including legs). They are mainly present in arid habitats such as semi-deserts and dry mountain slopes. Camel spiders are nocturnal, opportunistic predators that hunt anything they can overpower. Their preys include invertebrates, small vertebrates and even carrion beetles. Food is acquired and ripped using powerful mobile jaws (chelicerae) found in the mouth area. Pedipalps of camel spiders appear like an extra pair of hairy legs but their use if mainly sensory and defensive.
Ticks (Ixodidae)
Ticks belong to the parasitiform superorder of mites. They are well-known among vets and cattle breeders for their parasitism of big mammals, especially ruminants, but also dogs, etc. And they are also well-known among philosophers since Jakob von Uexküll’s analysis of ticks’ perception of their surrounding world. The biologist explained that the perceived world (Umwelt) of these blind and deaf arachnids can be reduced to only three perceptions: (1) The body sensitivity to light which make them climb on high grass; (2) The odor of butyric acid, which emanates from the sebaceous follicles of all mammals, and which makes them fall from the blade of grass onto the animal; (3) The heat of the mammal body that makes them search for the warmest spot where to suck the blood.
In Lebanon, identified hard ticks (Ixodidae) belong to 4 genera: mainly Rhipicephalus, but also Haemaphysalis, Dermacentor, and Hyalomma.
Bibliography
Mayssaa Fawaz Dabaja et al. 2017 “Diversity and distribution of ticks from domestic ruminants in Lebanon,” Veterinaria Italiana