The bugs that are found dead on their back in the house are poisoned. The presence of poison is found to be causing the muscle spasms to occur and making them to turn over. Â If a bug is flipped over, it can become upright by its own strength. But poison will not allow the coordination of the muscles to happen which will prevent the bug from turning upright. When they die, they turn on their back. The dead insect will lie in a position with the legs positioned upwards. This position is generally considered a problem for the bug because of the pain due to its reduced muscle coordination. The bugs while lying on their backs will possess failed nervous systems.
Generally, when a bug is made to position itself on its back, it can become upright again with the help of its legs. It might not roll back to its right position on its abdomen as it might have become very weak or due to its nervous system not functioning properly. Because of these reasons, the bug is stuck on its back.
In this flip position, the bug will not be in a position to get the desired nutrients; it will not be able to protect itself from predators if it is lying without any movement on its back. If the bug cannot turn upright, it will not be able to flip back again. There might be many things that are responsible for making the bug lie on its back and not turn over. The insecticides and pesticides will hinder the neurotransmitters in the bug, and they will stop the functioning of the nervous system. The insecticide will make the insect to undergo convulsions which will cause the bug to kick its legs upwards without any control and get struck like that. As the nervous coordination of the bug gets reduced, the bug will lose the ability to get all its legs into one position and roll over to the upright position. Based on the intensity of the poison, the bug will be killed within few hours or days.
Any injury or a state without food can also make a bug turn on its back and not position itself upright. Another reason for it not to be able to come back to its original state is probably it has reached the end of its lifespan and has lost its strength to gain its coordination abilities.