ABSTRACT
Introduction Photoperiod and the temperature are the most stable abiotic rhythms on the earth, and they are considered to be the principal exogenous factors that aect daily periodicity of behaviors of all organisms, particularly nocturnal feeders [1]. Nonetheless, many cues, including biotic factors, are available to foraging organisms, and each cue may have dierent potentials in determining daily activity patterns. For example, biotic factors such as predation or foraging ability based on sensory modalities would inuence diel activity patterns. What is not well understood is how abiotic and biotic factors act in concert to regulate the daily activity patterns of foraging organisms. For example, studies of the eects of photoperiod on herbivorous insects typically place the insects on host plants, and behaviors are observed during dierent photoperiods. However, in addition to the light-dark cycle, the host plant is also potentially inuencing the behavior of the insect because host plants are often not only food sources for herbivorous arthropods, but also their microhabitats. Host plants release odors, or volatiles, that have been shown to be inuenced by photoperiod [2]. us, herbivorous arthropods are also confronted with a number of plant factors that potentially vary according to photoperiod and temperature, and it is critical to understand the role of each of these factors when determining the mechanisms regulating diel activity patterns.
