Source: Development and Ecological Role of Neem in India

Neem has been reported to control at least 125 species of pest insects, mites and nenatodes, including 25 species of Coleoptera (beetles), 10 species of Diptera (flies), 25 species of Leptdoptera (moths) and 9 species of Orthoptera (locusts).  The following is a list of some of the insects that are affected by neem products.
 

American Cockroach: Reduces fecundity and molts, reduces number of fertile eggs.

Bean Aphid: Reduces fecundity, disrupts molting.
Boll Weevil: Inhibits feeding.
Brown Planthopper: Inhibits feeding repellent, disrupts growth, making failures and sterility.

Cabbage Looper: Inhibits feeding
Colorado Potato Beetle: Eggs fail to hatch, larvae fail to molt with azadirachtin levels as low as 3ppm inhibits feeding.
Confused Flour Beetle: Inhibits feeding, disrupts molting, molting, toxic to larvae.
Corn Carworm: Retards growth, inhibits feeding, disrupts molting
Cowpea Weevil: Inhibits feeding, toxic.

Diamondback Moth: Strongly suppresses larvae and pupae, retards growth, inhibits feeding.

Face Fly: Retards growth, toxic
Fall Armyworm: Retards growth, repels adults, inhibits feeding, disrupts molting, toxic to larvae.
Flea: Retards growth, repels, inhibits feeding, disrupts growth, eggs fail to hatch.
Flea Beetle: Inhibits feeding.
Fire Ant: Inhibits feeding, disrupts growth.

Green Leafhopper: Inhibits feeding.
Gypsy Moth: Retards growth, inhibits feeding, disrupts growth.

Head Lice: Kills, very sensitive to neem oil - traditional use in Asia.
Horn Fly: Repels, retards growth, disrupts growth.
Housefly: Inhibits feeding, disrupts molting, repels.
House Cricket: Disrupts molting.
House Mosquito: Toxic to larvae.

Japanese Beetle: Repels, retards growth, inhibits feeding, disrupts growth.

Khapra Beetle: Inhibits feeding, disrupts molting, toxic to larvae.

Large Milkweed Bug: Toxic, disrupts growth.
Leafminer: Retards growth, inhibits feeding, disrupts molting, toxic.

Mealy Bugs: Repels, inhibits feeding.
Meditterranean Fruit Fly: Disrupts growth, toxic.
Mexican Bean Beetle: Retards growth, inhibits feeding, disrupts molting.
Migratory Locust: Stops feeding, converts gregarious nymphs into solitary forms, reduces fitness, adults cannot fly.
Milkweed Bug: Difficulty in escaping the "skin" of the last molt, disrupts molting.

Oriental Fruit Fly: Arrest pupae development, retards growth, toxic to larvae.

Pink Hollworm: Retards growth, inhibits feeding.

Red Flour Beetle: Inhibits feeding, toxic.
Rice Gall Midge: Toxic.
Rice Weevil: Inhibits feeding, disrupts growth, toxic.

Serpentine Leafminer: High pupal mortality, retards growth, inhibits feeding, disrupts molting, toxic to larvae.
Sorghum Shoot Fly: Inhibits feeding.
Spotted Cucumber Beetle: Retards growth, inhibits feeding.

Tobacco Budworm: Inhibits feeding.
Tobacco Hornworm: Inhibits feeding, disrupts growth, toxic.

Webbing Clothes Moth: Inhibits feeding, disrupts molting.
Western Thmps: Retards growth.
Whitefly: Repels, retards growth, inhibits feeding.

Yellow-fever Mosquito: Kills larvae, disrupts molting.