Capnodis tenebrionis (L. 1758) (Coleoptera: Buprestidae): Morphology and Behaviour of the Neonate Larvae, and Soil Humidity Effects on the Egg Eclosion

Abstract

Capnodis tenebrionis (L. 1758) is reported for several countries of the Mediterranean subregion as a common phytophagous insect of many cultivated and wild species of trees and shrubs belonging to the family Rosaceae. Infestations on stone-fruit orchards have economic effects and can often cause the death of the plants in consequence of larval tunnelling into the roots. Egg laying occurs in late spring and summer on the trunk base or nearby in the soil. The importance of the neonate larval skills in relation to the biological success of this pest has stimulated its morphological, ecological and ethological studies to better understand the hatching mechanisms and the mortality effects of humidity on the eggs. In the present contribution, the morphology of the first larval instar is described throughout and illustrated, and the morphological details are compared with those of the mature larva. A survey on the hatching mode points out that neonate larvae, wherever eggs are laid, always come into contact with the soil. Finally, hatching rates were determined under laboratory conditions at four soil moisture levels, expressed as percentage of the Field Water Holding Capacity. A comparison was made with respect to a control of dry soil. The results prove that soil humidity significantly affects the egg eclosion, especially at the higher values.