Rhinoceros beetles with a weight of up to 3g were used in this experiment because they can carry the controlling module (weighing about 1.3g) on their backs. And another reason is that they look cool, according to the university.
So what’s the point of this exercise? Considering that the Defense Advanced Research Projects Agency (DARPA) is funding the research, military purposes are a likely contender. Commenting on this point, the university said that the technology can also be utilized for peaceful purposes. For instance, the radio-controlled beetle can be useful in places that are too narrow or dangerous for a human to enter and for many other purposes.
For that use, the university is planning to mount sensors including a camera on a beetle in the future. With the sensors, rhinoceros beetles will be able to work as surveillance robots in place of humans. As they can carry a weight of 3g, 1.7g of sensors, in addition to the 1.3g of the current module, can be mounted.
However, the ultimate goal of this research goes beyond just incorporating sensors. Beetles are already equipped with "sensors," such as their own eyes. In addition, they have a system to derive energy from food. So, the university is aiming to make the most of insects' own sensors while using their energy system as batteries.
I think we are on a slippery slope with this one. Attack of the Rhino Beetle? I might have trouble sleeping tonight.