THE ENERGETIC STATE OF IPS-TYPOGRAPHUS L (COL, SCOLYTIDAE) DURING THELIFE-CYCLE

The energetic state of adults of the European spruce engraver I. typog raphus was investigated during different stages of the life cycle: mat uration feeding, hibernation, dispersal, and just after starting to ex cavate brood galleries. The beetles were characterized by the pattern of free amino acids and especially by the concentrations of proline an d alanine. Additionally the lipid concentrations were estimated. In co mparison to all adults investigated, only newly moulted beetles showed the highest content of amino acids and a large variety of those amino acids which can be integrated in proteins. The process of sclerotizat ion during the maturation feeding was accompanied by an increase in li pid content and a decrease in the amount of amino acids, with the exce ption of proline and alanine. In all further physiological stages of t he beetles, proline and alanine were found to be dominant. Proline and alanine constituted, in total, 70-80% of the free amino acids. During dispersal, the sum of proline and alanine ranged between 95 and 130 n mol/mg dry matter, whereas, before and after hibernation, as well as i n breeding adults, the corresponding values varied between 60 and 75 n mol/mg dry matter. The concentrations of alanine reached considerably higher amounts in the flying stages. Depending on the date of emergenc e, the lipid content of the adults (expressed as mu equi x acylesters/ mg dry matter) varied as follows: 0.32, 0.75 and 0.89. During hibernat ion, the lipid content was reduced by about 60%. The results indicated that flying adults have a proline/alanine shuttle system by which ene rgy-rich compounds derived from the degradation of lipids are distribu ted within the insect. In line with this hypothesis, the energetic sta te of flying beetles is characterized by two parameters: 1. The lipid content representing the total energy reserves which are potentially a vailable; and 2. The ratio of the concentrations of proline and alanin e being regarded as a measure of the energy which is actually availabl e for respiration during flight. Increasing values of the proline/alan ine-ratio indicated higher levels of fuels for respiration. This appro ach was used to characterize the energetic state of dispersing beetles . During dispersal, attacked trap-trees seemed to be more attractive t o I. typographus, especially to females, than pheromone traps.