Why does Allah U give the parable of a mosquito and not an elephant, which is the biggest and greatest animal? The people of that time belittled the mosquito because their human intellect at that period had not yet seen the importance of the parable of a mosquito. However, the companions of the Prophet r accepted the Holy Qur’an exactly as it was recited unto them by the Prophet r and believed in it because it was from Allah r. The disbelievers, on the other hand, debated and questioned without real understanding.
As knowledge advances, things get smaller and inventions get more delicate. To illustrate this point, when the watch was first invented, it was large. As knowledge got more advanced, it got smaller and smaller as they became more and more capable of fitting more complex systems into smaller spaces.
The mosquito consists of a most delicate system which all the dwellers of Earth fall short of comprehending it.