THE ORIENTATION RESPONSE OFCTEMCERA DESTRUCTORAND OTHER WIRE WORMS (COLEOPTERA: ELATERIDAE) TO GERMINATING GRAIN AND TO CARBON DIOXIDE

Abstract

Several species of wireworms were attracted to germinating wheat, air from flasks of germinating wheat, decomposing oatmeal, commercial CO₂and, in addition, germinating seeds of eight other cultivated plant species. Larvae located a biological or experimental source of CO₂by a directed movement along CO₂gradients, from distances up to 20 cm.Methods and apparatus for measuring small CO₂gradients, using gas chromatography and mass spectrometry, are described.Ctenicera destructor(Brown) larvae apparently responded to CO₂gradients between glass plates, that ascended on the average by 0.002% (soil) and 0.005% (agar)/cm over a distance of from 12 to 16 cm. The "sensitivity threshold" was calculated as being 1–2 ppm over the distance involved in one deflection of the head during klinotactic orientation. Attractancy was observed within a range of CO₂concentration from about 0.036% to 1.5%. Repellent effects did not appear to be only related to concentration, but possibly were due to steepness of the gradient and(or) previous exposure to CO₂.Passing an air stream from germinating grain over a KOH solution eliminated the attractancy of the grain by removing the CO₂and possibly other undetected attractants. A small percentage ofC.destructorlarvae apparently oriented to an ethylene source, but it was concluded the CO₂was the most important if not the only attractant from germinating wheat seeds.