Insects molting process

Figure 2. Critical events in the normal insect molting process relative to changes in 20E concentration.

Ecdysone. A hormone that stimulates the molting process in insects. 

To date, interest in the ecdysteroids has focused primarily on their role in insect molting and metamorphosis and it is perhaps somewhat unfortunate that bioassays for ecdysteroid activity have been restricted almost exclusively to evaluating their effect on the molting process. It now appears probable that molting is just one of several important regulatory functions (e.g., embryogenesis, reproduction) performed by the ecdysteroids and that we are only just beginning to scratch the surface of an insect steroid system that is equally as complex as that in vertebrate species. 

The growth of insects can be controlled by the disruption of the molting process by inhibiting chitin biosynthesis [23, 24]. Since the mid-1970s several fluorinated... 

In insects and arachnids, there are two main molting processes of the sensilla one which retains a dendritic connection between the old and the new sensillum, thus retaining the chemosensory function, and one where there is no such connection and the chemosensory function is presumably temporarily lost during the molt. The type without loss of chemosensory function is the more predominant one (Guse 1983). 

LCgQ is the lethal concentration in ppm of additive necessary to kill (usually by inhibiting ecdysis, the final stage of the molting process) 50% of the treated insects. 

In contrast, no insecticide has been developed to interfere specifically with the process associated with the steroidal insect molting hormone, 20-hydroxyecdysone. Although active ecdysteroids can be obtained from plant and animal sources (S), the main reason for the failure to develop them as insecticides has been that (a) their structures are too complex to produce economically, (b) their hydrophilic nature prohibits their penetration into insect cuticle, and (c) insects have powerful mechanisms to eliminate ecdysones between molts. One approach to solve these problems is to synthesize a simple molecule which can mimic ecdysone, but with appropriate chemical and transport properties, and acceptable metabolic stability. 

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