A circadian rhythm of daily activity and an annual rhythm are two primary rhythms recognized among animals, where an external signal (zeitgeber), typically light/dark daily rhythms or seasonal cycles acts to entrain the rhythm of an internal oscillator. In order to synchronize with daily factors, the circadian system should contain a photoreceptor (s) which may be placed either in the visual (ocular pathway) or in non-visual (extraocular pathway) organs. In addition, non-photic factors (like thirst), may interact with the circadian cycle in determining the operation of biological clocks. Generally, a circadian rhythm should persist in the absence of a periodic zeitgeber cue, but some behavioural processes in arthropods do not seem to follow this idea of a classic internal oscillator. In these cases, the timing mechanisms are referred to as ‘hourglass’ models. In nocturnal animals, light inhibits activity, whereas it boosts activity in diurnal animals. Direct effects of light result in a phenomenon called “masking effects” which veil the actual entrained circadian activity rhythm (s). With more than 6000 described species in more than 600 genera, the Salticidae is a large family of diurnally-active cursorial spiders. I investigated aspects of the temporal behaviour of salticids in this thesis in a series of experiments measuring activity patterns over a period of several days. I begin with a series of comparative experiments using four salticid species to investigate the effects of temperature and light duration on the locomotory activity patterns, depending on sex and age. I found that circadian activity patterns differed widely between species and, within species, also differed depending on both temperature and photoperiod. I then explored the effect of reproductive status and food-related effects (e.g., hunger, thirst) on the locomotor activity of female Portia fimbriata and Marpissa marina. Thirsty spiders, and those fed preferred prey prior to testing had increased activity levels, while females that had recently laid eggs became almost inactive. I then investigated short-term temporal effects on salticid behaviour across different light regimes simulating different latitudes. I found no support that M. marina adhere to hourglass models of timekeeping, instead relying on circadian clocks with a period of close to 24 h to maintain a thoroughly resilient diurnal pattern of behaviour despite showing differential responses to phase advances and phase delays. Subsequently, I described the timing of locomotor activity at different light levels within a 12:12 LD simulation in Marpissa marina, finding that anticipation of the start and end of daylight hours is related to light intensity during daylight hours. Additionally, low level moonlight illumination significantly increased activity compared to total darkness. A clear masking effect on the spiders’ clock was found under bright light, in which condition M. marina were no longer able to anticipate lights-on and lights-off. I then investigated Aschoff’s rule using M. marina in conditions of constant darkness and constant light at different intensities to determine the effect of different light intensities in their free-running period. Depending on the intensity of light, constant light can disrupt circadian rhythmicity in M. marina, with a variety of responses exhibited, ranging from reduced locomotion and an increase in tau (the difference angle between the onset of activity and light-on time) to complete arrhythmicity (loss of daily rhythms over successive cycles). Finally, in a series of eye covering experiments, I investigated which of the four pairs of eyes were capable of entrainment, finding that the ‘secondary’ eyes, but not the ‘primary’ eyes were used to synchronize the circadian clock.