Effects of temperature and light on calling in the tiger moth Holomelina lamae (Freeman) (Lepidoptera: Arctiidae)

ABSTRACT. In Holomelina lamae Freeman daily eclosion of adults is gated, with males emerging before females. By advancing the onset of photophase and by delaying the onset of scotophase, it was demonstrated that lights-on acts as the main phase-setting cue for calling. Few females call on the day they eclose. Calling is initiated c. 9 h after the onset of photophase in 2-day-old females, and shifts to earlier times in older females. The duration of calling also increases with age. That calling is controlled by an endogenous circadian clock is indicated by its persistence in continuous light (LL) and dark (DD). In LL calling is dampened rapidly, but a single scotophase re-entrains the rhythm. Decreases in temperature advance the onset of calling and the mean hour of calling, while increases in temperature delay both. However, the magnitudes of such phase-shifts depended upon hour of the photoperiod. Moreover, cooling and heating appears to exert both transient and long-term effects on the calling rhythm. An 8 h period at a reduced temperature in LL induces calling in females whose calling is dampened, and entrains the calling rhythm. Females maintained in DD from second instar larvae to the adult stage exhibit a circadian calling rhythm set by eclosion.