Beedrill mostly resembles a bipedal, yellow wasp; however, it only has four legs instead of six and lacks pigment pits. Beedrill's head is round with a slightly pointed mouth, large, red eyes, and black antennae with a sharp bend in the middle. Its forelegs are tipped with long, conical stingers. It stands on its other two legs, which are long, segmented, and insectoid in shape. Beedrill has two pairs of rounded, veined wings, and another stinger on its yellow-and-black striped abdomen.
As Mega Beedrill, its gains more defined features. The antennae are shorter and now extent forward and back over its head. Its eyes become longer and sleeker. It now has three pairs of wings; the uppermost pair is larger with a black trim along the top. Its stingers become longer and larger, resembling javelins. Its legs are no longer insectoid, and instead resemble conical, black-and-yellow stingers with white tips. Its abdomen becomes larger and grooved, and is attached to its thorax by a black structure. A similar black structure connects its head and thorax. The stinger on its abdomen is now a pale yellow, and it now has black stripes over its entire body. Fast-acting poison is stored in the stingers on its limbs, while the tail stinger produces a slow-acting poison that is used to finish opponents. The instantaneous poisons are instead used to prevent the foe from fleeing.
Beedrill is highly territorial and normally lives in colonies. Beedrill seems to be especially concerned with the welfare of Weedle and Kakuna, and it will respond aggressively to those that disturb them. Disturbing a swarm of Beedrill will cause the whole colony to attack. It flies at high speed and attacks using the large venomous stingers on its forelegs and abdomen. The two stingers on its forelimbs allow it to use its former signature move, Twineedle. It will take the victims of its attacks back to its nest for food. Beedrill nests in forests and misty wooded areas.
Beedrill can be seen as a parallel to Butterfree. Both of their unevolved stages evolve into their respective first evolutionary stages at level 7, which then evolve into their respective final forms at level 10. They both also go through metamorphosis-like evolution and share a base stat total of 395. Also, while Beedrill is a version exclusive of Black and Black 2, Butterfree is exclusive to White and White 2.
Mega Beedrill has the highest Attack and Speed base stats of all Poison-type Pokémon. It also has the lowest Special Attack base stat of all Poison-type and Mega Evolved Pokémon, and the lowest single base stat of any Mega Evolved Pokémon.