Which of the following is a notable feature of Gyrinidae?

Which of the following is a notable feature of Gyrinidae?

• A. Front legs long, back two pairs short and flattened
• B. Wings fused to abdomen
• C. Antennae extremely long
• D. Elytra completely covering abdomen

Answer: (A)

Gyrinidae are specialized surface-swimming beetles whose legs reflect their aquatic lifestyle. The front legs are relatively long and are used to grasp prey or help maneuver, while the middle and hind legs are shortened and flattened to act like oars for rapid propulsion on the water. This combination lets them zip around the water’s surface and respond quickly to prey or threats, a hallmark of whirligig beetles. Other features listed don’t fit their biology: they do not have wings fused to the abdomen, and their elytra do not completely cover the abdomen—these beetles have short elytra that leave part of the abdomen exposed. Their antennae are not unusually long, and their most notable trait isn’t wing fusion or extremely long antennae but the leg arrangement that supports surface swimming.

Gyrinidae are specialized surface-swimming beetles whose legs reflect their aquatic lifestyle. The front legs are relatively long and are used to grasp prey or help maneuver, while the middle and hind legs are shortened and flattened to act like oars for rapid propulsion on the water. This combination lets them zip around the water’s surface and respond quickly to prey or threats, a hallmark of whirligig beetles.

Other features listed don’t fit their biology: they do not have wings fused to the abdomen, and their elytra do not completely cover the abdomen—these beetles have short elytra that leave part of the abdomen exposed. Their antennae are not unusually long, and their most notable trait isn’t wing fusion or extremely long antennae but the leg arrangement that supports surface swimming.