Pyriproxyfen is a pyridine

Pyridine

Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...

 based pesticide which is found to be effective against a variety of arthropod

Arthropod

An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

a. It was introduced to the US in 1996 to protect cotton crops against whitefly

Whitefly

The whiteflies, comprising only the family Aleyrodidae, are small hemipterans. More than 1550 species have been described. Whiteflies typically feed on the underside of plant leaves.-Agricultural threat:...

. It has also found useful for protecting other crops.
It is also being used as a prevention for fleas on household pets.

Pyriproxyfen is a juvenile hormone analogue

Juvenile hormone

Juvenile hormones are a group of acyclic sesquiterpenoids that regulate many aspects of insect physiology. JHs regulate development, reproduction, diapause, and polyphenisms....

, preventing larvae from developing into adulthood and thus rendering them unable to reproduce.

In the US pyriproxyfen is often marketed under the trade name Nylar. In Europe pyriproxyfen is known under the brand names Cyclio (Virbac) and Exil Flea Free TwinSpot (Emax).