How do some insecticides affect an insects spiracles?

Insecticides are nerve agents that enter the spiracles and cause different molecular effects depending on where they act, summarily, killing the insect. See Klaassen and Watkin's Chapter 22. Casarett and Doull's Essentials of Toxicology. Usually the insecticide acts on enzymes such as acetylcholinesterase or on ion channels such as sodium channels