Defensive secretion production in the tenebrionid beetle,Zophobas atratus : Effects of age, sex, and milking frequency.

Beetles were milked of their abdominal defensive secretion at three different frequencies over the first 36 days of adult life. Secretion production decreased greatly with age from a maximum of 94 nmol/day at 4-6 days to a basal level of about 25 nmol/day at 30-40 days. Ethyl- and methylquinone comprised the bulk of the secretion and were most strongly affected by age. Benzoquinone was most strongly affected by milking frequency. An average adult produced an estimated 4445 nmol of total secretion in its 5-month life-span but had reservoirs large enough to store 11,000 nmol. Males produced more secretion than females because of their larger size and inherent sexual differences. As they aged, mated females showed a more rapid decrease in production that virgin females. The defensive system appears to be programed to charge glands rapidly with secretion early in adult life and fall of to a low recharge rate little affected by discharge.