ECOLOGICAL STUDY ON THE COFFEE STEM BORER <I>XYLOTRECHUS QUADRIPES</I> CHEVROLAT (COLEOPTERA: CERAMBYCIDAE) IN NORTHERN THAILAND I. DESCRIPTION OF STAGE AND BIOLOGY

Abstract

The ecology of coffee stem borer, Xylotrechus quadripes Chevrolat (Coleoptera: Cerambycidae) was studied in the laboratory (29-31 °C) and under the field conditions in 1990-1991. The result of description of stage and biology in the laboratory revealed that a female long hom beetle produced 7-238 eggs with the average of 103 during its life time. The incubation period of the egg was about 5 days on average. Precise measurement of the head capsules of the larvae indicated that there were six instars. The mean of devlopemental period from larva to adult which fed in coffee stick was about 77 days while the larva fed in living plant was extended to 153 days. Life expectancy of male stem borer was counted as 24 days, incontrast, female was stayed about 5 days longer. Under natural conditions, the ratio of existing between male and female was 1: 2. However, slightly difference of the ratio was observed in the laboratory and it was 1: 1.3. A record of living period of the female which fed in coffee stick from egg untill its death was confirmedly averaged to about 91 days.

The survey of natural enemies of stem borer pointed out that there were 3 species of the Hymenopterous parasites from the families of Aulacidae, Stephanidae and Ichneumonidae. Among the observed parasites, Pristaulacus sp. which belonged to family Aulacidae gave a high potential as the natural enemies of stem borer. Therefore, such species should receive further investigation for utilization as augmentative biological control agent.