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How are insects different from arachnids?
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arthropod
Spiny lobster, or rock lobster (Palinurus elephas).
Although insects and arachnids are both members of the phylum Arthropoda, they are distinct taxonomic groups with several key anatomical differences.12
The primary differences include:
- Body Segments: Insects have bodies divided into three main sections: the head, thorax, and abdomen. In contrast, most arachnids have two main body regions: the cephalothorax (prosoma) and the abdomen (opisthosoma).23
- Legs: Insects possess six legs, whereas arachnids typically have eight legs.2
- Antennae: Insects have antennae, while arachnids lack them entirely.2
- Specialized Organs: Arachnids are characterized by the presence of chelicerae (often used as jaws) and, in the case of spiders, specialized silk-producing organs called spinnerets.234
While both groups share typical arthropod features—such as a segmented body, a tough exoskeleton made of chitin, and jointed appendages—these structural variations allow them to occupy diverse ecological niches.13