What do IGRs do to ants?

Insect Growth Regulators (IGRs) function by disrupting the normal hormonal processes that regulate an insect's growth and development. In the case of ants, IGRs inhibit their ability to complete their life cycle stages. Specifically, IGRs interfere with the development of larvae into adulthood, effectively preventing them from reaching the adult stage. This disruption can significantly reduce the ant population over time, as without mature adults to reproduce, the colony's ability to sustain itself is compromised.

The other choices do not accurately reflect the role of IGRs in ant populations. IGRs are not primarily designed to speed up growth or reproduction; rather, they hinder the development and maturation of ants in their life stages. Therefore, the statement that IGRs "do not allow them to become adults" is the most accurate representation of their function with regard to ant management.