PREDATION BY FORMICA-POLYCTENA FORSTER (HYM, FORMICIDAE) ON NEWLY EMERGED LARVAE OF NEODIPRION SERTIFER (GEOFFROY) (HYM, DIPRIONIDAE)

In a young lodgepole pine stand, high mortality of Neodiprion sertifer (Geoffroy) larvae was recorded near a nest of the red wood ant Formica polyctena Forster. Beyond 40 m from the nest, larval survival increased sharply. N. sertifer eggs often hatch at quite low ambient temperatures in spring. However, in the study year, the larvae emerged during an unusually warm period with mid-day temperatures between 22 and 26-degrees-C. Efficiency of ant predation is known to increase with higher temperatures. Thus, temperature may have been a major factor behind the observed high larval mortality. Further, the scarcity of previous records of ant predation on newly emerged N. sertifer larvae may be partly explained by unusual occurrence of consistently high temperatures during the emergence period.