Effects of Photoperiod on Sexual Maturation, Fat Content and Respiration Rate in Adult Locusta migratoria

The effects of photoperiod on ovarian development, fat content and respiration rate of adult Locusta migratoria were examined at 30℃. All locusts were maintained under crowded conditions as nymphs and adults except when oxygen consumption was determined. Female adults reared in short days (LD 12 : 12 h) developed eggs rapidly whereas those reared in long days (LD 16 : 8 h) remained sexually immature for a long time, supporting the results reported by others. Mature oocytes or eggs were found in short-day females by day 17. Body weight, as determined by dry weight, tended to be heavier in long-day males than in short-day males, but no significant difference was found between females reared at the two photoperiods during the first 50 days except at day 5. Fat content of the body increased rapidly during the first 20 days in both short days and long days. During the next 30 days, it declined rapidly in short-day adults, but remained at a high level in long-day adults. Respiration rates at rest were significantly lower in sexually immature long-day adults than in reproducing short-day adults. These results indicate that locusts reared in long days are characterized by suppression of reproduction, increased fat content of the body and reduced resting metabolic rate. The possible function and significance of these responses are discussed.