Springtails have a structure used to propel them when disturbed, which is shaped like a fork. What is it called?

The structure used by springtails to propel themselves when disturbed is called the furcula. This is a specialized anatomical feature that is forked in shape and is located on the underside of the springtail's abdomen. When the springtail is threatened or disturbed, it can rapidly release the furcula, which acts like a spring. This quick movement allows the springtail to jump away from dangers, making it an effective means of escape.

The other terms provided do not refer to the same structure. A fascia refers to a band or sheet of connective tissue in the body, a funnel typically describes a conical shape used for directing liquids, and a flagellum is a whip-like structure that aids in movement for some cells and microorganisms. None of these options describe the specific mechanism springtails use for jumping, which is why the furcula is the correct answer.