What's the difference between bees and butterflies?

Bees and butterflies belong to the class Insecta, an arthropod. Although earthworms (annelids) and mussels (mollusks) lower than insects already have hearts, annelids even have closed-loop circulation, and the circulation system has been very developed. But the circulatory system of insects has been greatly degraded. This is because insects have a well-developed tracheal system, which can directly deliver oxygen to various tissues and organs. The circulatory system is no longer responsible for transporting oxygen, but only nutrients and hormones. Therefore, the demand for the circulation system is reduced. At the same time, the limbs of this insect are very easy to break. If the blood pressure is too high, there will be too much bleeding after limb amputation. These factors make the circulatory system of insects seriously degenerate, from the closed loop of annelids to the open loop. The circulatory system also becomes inconspicuous. Some people think that insects have no hearts, which may be the reason. But although the circulatory system of insects has degenerated, it still has a heart. Take the grasshopper as an example (it is easier to dissect if it is big). Seven hearts can be found in series on the ventral side (opposite to the dorsal side) of the head, chest and abdomen near the shell. Accompanied by abdominal nerve cords, under the digestive tract.