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1. Trapping experiments and observations of sexual behaviour were made on Cephdciu laridphila in infested larch forests in Hereford and Worcester and Mid-Glamorgan in early May 1977.2. The results indicated that virgin females and dichloromethane extract of crushed virgin females were highly attractive to males.3. On 17 May males responded to females throughout the warmest part of the day. First response occurred before 09.00 hours, the last after 17.00 hours and peak activity was from 11 -00 to 14.00 hours.4. Mated females became unattractive to males within 10 min after mating. When mated females or males were paired with virgin females there was no evidence of an anti-attractive pheromone or pheromone mask. 5.A few males dispersed out of larch into adjacent spruce forests and were captured in virgin female-baited traps up to 135 m distant from infested larch. Virgin female-baited traps at 0-05 m from the ground captured over seven times the number of males as traps at 1,2 or 4 m, supporting visual observations that the preferred flight level for males is very near the ground.6. Horizontal board traps with an acetate surface coated with 'Stikem Special' were superior to Pherocon lC, vertical board and gypsy moth traps in that order.7. The observations and results suggest that the best applied uses of C.lariciphi[a pheromone would be in survey and detection, and male disruption techniques.

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