Arthropoda

6. – Chemical scents released by an animal to communicate with others of the same species (e.g., for mating or alarm).
7. gland – Excretory organ in the head of some crustaceans (like crayfish) that removes waste, similar to a kidney.
9. – A claw-bearing leg, especially the large pincers of crabs and lobsters.
10. – A subphylum of arthropods that includes spiders, scorpions, ticks, and horseshoe crabs; they have chelicerae (pincer-like mouthparts) instead of antennae.
11. – The tough, flexible material that makes up an arthropod's exoskeleton and protects the body.
13. – A simple eye (single lens) found in many arthropods, especially insects and spiders.
15. – An extinct class of ancient marine arthropods known as trilobites.
17. – An older name for a group of arthropods with unbranched (single-series) legs; includes insects and myriapods (centipedes and millipedes).
18. – The process of changing body shape through different life stages (e.g., caterpillar → pupa → butterfly).
20. – The aquatic young stage (larva) of insects like dragonflies and mayflies that breathe with gills.
22. – The hard outer skeleton that covers and supports an arthropod's body.
23. – Shedding the old exoskeleton so the arthropod can grow larger and form a new one.

1. – The large animal phylum that includes insects, spiders, crabs, etc.; all have jointed legs and an exoskeleton.
2. – Having a body made up of many repeating sections or segments.
3. – The fused head-and-chest body region found in spiders, scorpions, and crustaceans.
4. – Small breathing hole on the side of an insect or some other arthropod's body that lets air into the tracheae.
5. – The stage of an arthropod's life between two molts (e.g., a caterpillar in its 3rd instar).
8. – The class that includes millipedes; they have two pairs of legs per body segment.
11. – A group of mostly aquatic arthropods such as crabs, lobsters, shrimp, and barnacles; usually with two pairs of antennae.
12. – A young stage of certain insects (like grasshoppers) that looks like a small version of the adult but without fully developed wings.
14. – An early, immature life stage of an animal that looks very different from the adult (e.g., caterpillar, maggot, nauplius).
16. – The resting, transformation stage in complete metamorphosis (e.g., cocoon of a butterfly or chrysalis).
19. – A leg, antenna, or other body part that sticks out from an arthropod's body.
21. – Having separate male and female individuals (not hermaphroditic).