Effects of precocene I and II on the sensory system of antennae and mouthparts of Colorado potato beetle larvae, Leptinotarsa decemlineata (Col.: Chrysomelidae)

The chrysomelid species Leptinotarsa decemlineata (Say), commonly known as Colorado potato beetle (CPB), is an important pest of potato and other solanaceous crops. The effects of precocene I and II, juvenile hormone inhibitors, on morphological characteristics of the chemoreceptor organs of antennae and mouthparts of L. decemlineata larvae were studied in the laboratory. Different doses of precocenes were applied on the CPB second-instar larvae. The results showed that precocene caused changes in the form and number of sensilla of the antennae and maxilla-labial complex. The treatment of second-instar larvae by precocene I and II, considerably changed the cuticular structure of antennae and labio-maxillary palps after the first molt. In addition, other anomalies such as remaining of the previous instar cuticle, degeneration of some or whole sensilla on the second and third antennal segments and on the terminal segment of labio-maxillary palps, and reduction of both receptor cells and their dendrites were observed. The effects of precocenes on the insect sensory system and disturbance of chemical recognition of host plants and environment are discussed.