菜青虫是菜白蝶的幼虫。分布广、危害重,是十字花科蔬菜主要害虫之一。其色青绿,背面满布黑色小点,上生细毛;各节上有横列皱纹,气门附近有黄色小点,组成一条黄色线纹。菜白蝶适应性广,繁殖迅速,在湖南一年发生8～9代,以蛹在屋檐、篱笆、树皮缝隙及枯枝落叶等处越冬。发生不整齐,世代重迭。成虫以3月上中旬、4月中下旬、6月上中旬、9月中下旬、11月上中旬出现 Pieris rapae is a butterfly larvae. Widely distributed, endangering heavy, is one of the major pests of cruciferous vegetables. The color of green, the back covered with black dots, students fine hair; each section has a row of wrinkles, yellow dot near the valve to form a yellow line pattern. Cabbage butterfly wide adaptability, rapid propagation, occurred in Hunan 8 to 9 generations a year, pupa in the eaves, fences, bark crevices and litter at the winter. Occurred irregularities, generations overlap. Adults in mid-March, mid-late April, mid-June, mid-late September, mid-November appeared