Pictures of Invertebrates
. Black Widow Spider The female black widow spider, distinguished by the red hourglass marking on the underside of her abdomen, is probably the best known and most feared of all North American spiders. In spite of the female black widow’s small size of 1.2 cm (0.5 in.), its venom is quite toxic and may cause a wide range of symptoms in humans, including pain, swelling, nausea, and sometimes death. The male of this species is harmless to humans and lacks the hourglass marking on the abdomen. Blue Spotted Sea Urchin This underside view of the blue spotted sea urchin shows its mouth apparatus, commonly called Aristotle’s lantern. This structure is composed of five jaws arranged in a radial, or concentric, pattern. This arrangement allows the sea urchin to feed efficiently on a variety of marine algae and kelps. Branching Coral Colonies Branching coral is actually a colony of very small individual animals called coral polyps. Branching corals are considered hard corals, since they have a h...