Being a substance meant to kill insects, insecticides can be of different kinds, as they attack insects at different stages of life. Insect growth regulators are meant to inhibit the development of these pests, and depending on what type of pests you are fighting against, you can use ovicides and larvicides, to make sure you stop their growth and reproduction. They are also divided by their ability to alter the ecosystems they come in contact with, as some have a residual, long term activity and others kill on contact. Insecticides can also be categorised by their natural, biological kind and synthetic, chemical structure.
They can be in solid, liquid or gaseous form, and depending on a different category, they can be classified by whether they will be toxic to unrelated, non-targeted species. Insecticides can also be repellent or non-repellent, with the latter killing slowly, but managing to eradicate more individuals from a colony, as they cannot detect the insecticide and carry it to their nest.
Nearly all insecticides have the potential to significantly alter ecosystems and some are even toxic to humans.