A comparison of Aphidecta obliterata (L.) (Col., Coccinellidae) populations feeding on Elatobium abietinum (Walker) and on Adelges cooleyi (Gillette).
Aphidecta obliterata was the main coccinellid species feeding on both Elatobium abietinum on Picea sitchensis, and Adelges cooleyi [Gilletteella cooleyi] on Pseudotsuga menziesii in a forest near Aberdeen, UK, during the pre-diapause imaginal period. Coccinella septempunctata and Adalia decempunctata were found on Picea only following emergence from the pupa and rapidly dispersed as the aphid prey was absent. The superiority of E. abietinum as a diet in comparison with G. cooleyi was shown by the higher dry weights of adults from larvae feeding on the former. A higher fat:dry weight ratio on Picea was additional evidence for this diet's superiority. A low respiration rate in comparison with post-diapause individuals indicated the necessity to conserve energy during the absence of prey in summer. Those coccinellids on P. menziesii exhibited a further respiratory rate depression in autumn which may be associated with energy conservation for overwintering. There was no evidence of differential elytral melanic pigmentation between the 2 populations.