Generally Recognized As Safe (GRAS) is a food substance designation put forth by the FDA. GRAS substances can be used in food under specified conditions as long as the safety of the substance can be validated.
There are two paths to achieve GRAS status. One is through scientific procedures with data being generally available. The second path, for a substance used in food before 1958, is through experience based on common use in food. This is kind of vague but check out this link:
Do insects meet GRAS requirements? Insects have been consumed for food throughout human history. There are also experts in the science community that promote the wholesomeness of insects as food. There are no known hazards associated with consuming insects except for allergies. Domestically farming insects using good manufacturing practices will reduce or eliminate the risk of common hazards such as pesticide residue.
I do not agree with Edible insects: future prospects for food and feed security’s interpretation that insects are additives. Insects used in food are GRAS and therefore do not default to a food additive status. Additives require premarket approval.
Commonly consumed edible insect in the US such as meal worms, crickets and wax worms should be considered GRAS.
FDA approval of GRAS substances is not required before using them in food. There is a GRAS notification program to notify the FDA of a substance but it is not necessary. The program either confirms your determination or disagrees.
Article: Is the GRAS Process Broken?