Insects of Texas: A Practical Guide

Arachnids

Arachnids Class: Arachnida (uh-raK-nih-duh) arachne, spider Characteristics: Size: variable; very tiny to >4 in. (10 cm) Shape: Two body segments, sometimes indistinguishable Antennae: absent Mouthparts: Possess chelicerae and pedipalps; pedipalps often modified as pinchers Eyes: Usually present Wings: absent Legs: Four pairs Habitat: Mostly terrestrial Food: Most predaceous on other arthropods This large group includes the very common and well-known spiders, scorpions, harvestmen, mites, and ticks. Some less common and infrequently observed members are the large whipscorpions, the very tiny pseudoscorpions, and the windscorpions. This class of arthropods is recognized by having a two-segmented body. The head and thorax are combined to form a cephalothorax to which the legs are attached. The abdomen is distinctly separated from the cephalothorax in some groups (spiders) but is indistinguishable in others (mites and ticks, harvestmen, and others). all members of this class possess four pairs of legs as adults. arachnids have specialized mouthparts composed of the chelicerae and pedipalps. The chelicerae hold the prey and serve as the fangs in spiders or as jaws in other members of the class. The pedipalps are often fingerlike (spiders, ticks, and mites). However, the pedipalps can be distinctly modified to form pinchers (scorpions), or they may be long and leglike (windscorpions). Some members, particularly the spiders, are venomous and secrete their toxin from poison glands through their chelicerae. The scorpions, however, immobilize their prey with a stinger located at the end of their abdomen. Most species are predaceous on other arthropods and are considered beneficial. Common orders in the class Arachnida Order Page Spiders: Araneae 33 Scorpions: Scorpiones 34 Whipscorpions: Uropygi 35 Harvestmen: Opiliones 36 Mites and ticks: Acari 37 Pseudoscorpions: Pseudoscorpiones 38 Windscorpions: Solifugae 39 32 arachnid arachnida 33 subdue it and finally wrap it in silk to keep the meal fresh. other spiders produce silk parachutes used to catch puffs of air to carry them to new areas. Female spiders lay their eggs in silken sacs and typically guard them, at least until the eggs hatch. The young spiders, called spiderlings, resemble the adults but are smaller and may stay with the female for a short time. all spiders are predaceous, feeding on other arthropods, and are considered beneficial. although all spiders produce venom, only a very few species are considered dangerous to humans. in Texas, the black widow, Latrodectus mactans, and the brown recluse, Loxoceles reclusa, are common poisonous spiders. Spiders order: araneae (uh-ray-nee-ee) Characteristics: Size: F to >4 in. (3.2 mm to 10 cm) Shape: Two distinct segments: cephalothorax and abdomen Antennae: absent Mouthparts: Piercing/sucking; fingerlike pedipalps Eyes: Present; six to eight Wings: absent Legs: Four pairs Miscellaneous: Abdomen not segmented Habitat: Mostly terrestrial; variable Food: Predaceous on other arthropods Spiders are easily recognized and generally unwelcome in human habitats. They can be distinguished from other arthropods by their two distinct body segments, four pairs of legs, and fingerlike pedipalps. Spiders are well known for their silk, which is used in a variety of ways. orb spiders make elaborate aerial webs to capture prey. once prey is entangled in the web, the spider will often spray more silk onto the struggling victim to garden spider with prey Black widow, Latrodectus mactans Brown recluse, Loxosceles reclusa 34 arachnida Scorpions order: Scorpiones (skor-pee-aH-nees) Characteristics: Size: Up to 2 S in. (6.4 cm) Shape: Abdomen broadly joined to cephalothorax; last five segments narrow and tail-like Antennae: absent Mouthparts: Piercing/sucking; enlarged pincherlike pedipalps Eyes: Present Wings: absent Legs: Four pairs Miscellaneous: abdomen segmented Habitat: Arid regions Food: Predaceous on insects and spiders Scorpions are easily recognized by their enlarged, pincherlike pedipalps and segmented abdomen that narrows into a tail that ends with a sting. Scorpions have a pair of eyes on top and in front of the cephalothorax and additional pairs on the lateral edges. Their vision, however , is poor, and they mainly rely on other senses. Scorpions are nocturnal predators that are most common in arid regions. During the day, they hide under rocks and other shelters on the ground. at night, they use comblike structures called pectines located under their abdomen to navigate and sense the presence of other organisms. Scorpions use their venomous sting to subdue prey and to defend themselves . The sting of most Texas scorpions is comparable to that of a honey bee or paper wasp and not considered life threatening. Scorpions typically...