The mesothorax and metathorax are rather intimately fused together.
The number of spiracles is greatly reduced; in the adult a pair is present on the mesothorax, sometimes also a pair on the metathorax, and there is always a pair on the first and another pair on the eighth abdominal segment.
readily movable on the mesothorax, an arrangement usual among insects with the power of rapid running.
The males are very small, free-flying insects with the prothorax, mesothorax and elytra greatly reduced, the latter appearing as little, twisted strips, while the metathorax is relatively large, with its wings broad and capable of longitudinal folding.
readily movable on the segment (mesothorax) immediately behind - smaller and of less importance where the prothorax is fixed to the mesothorax, as in bees and flies.