The evolution of the organisms is the result of a complex and changing interaction (geno and pheno) with environment, on the basis of powerful and extraordinary efficient chemical machinery. During the development’s process three fundamental points define, evolutively, the success of it 1.the cell-internal control mechanisms, 2.external control of the cell, and 3. links between the environment and genes. The transformations of insects and typical invertebrates during the larval states (metamorphosis) in their life’s cycle is an example of the chemical signals system and mentioned above point 1. The ecdysone, the so-called “moulting and metamorphosis” hormone, following the classic steroids action mechanism, is produced by the prothoracic glands, after activation induced by neuropeptides. This compound ( and its derivatives) controls the morphogenesis and metamorphosis. In biological systems where target-chemical compound interactions define the cell internal control, the chemical reactivity as a quantitative term, depends of optimum geometric, electronic and chemical properties. Ecdysteroid activity of several naturally occurring and synthetic steroidal derivatives, starting from ecdysone and diosgenine, have been studied in the past 20 years and some interesting results have been achieved. This communication intends: 1- Quantitative determining which are the key points of the ecdysone molecule and analogues that trigger the action of the biological machinery, starting from the structure-activity relationship and the analysis of electronic properties, using a very simple protocol, and, 2-Propitiating a mathematical-statistic tool that allows to discriminate most active molecules from the less active ones, optimizing the synthesis of steroidal analogs with define ecdysteroid action, useful for applying in field conditions for controlling insect pests which affect the crop yields.