Nocturnal Myrmecia ants have faster temporal resolution at low light levels but lower adaptability compared to diurnal relatives

Visual physiology of Australian stingless bees

Stingless bees engage in a range of visually guided behaviours that require relatively high spatial resolution and contrast sensitivity. Although the eyes of honeybees, bumblebees, carpenter bees, and sweat bees have been studied extensively, there is limited knowledge of stingless bees. Here, we studied two sympatric Australian species, Tetragonula carbonaria and Austroplebeia australis, which are important crop pollinators. The bigger A. australis had more and larger ommatidial facets compared to T. carbonaria. Using pattern electroretinography, we showed that A. australis had higher contrast sensitivity (13.07) compared to T. carbonaria (5.99), but their spatial resolving power did not differ (0.53 cycles deg-1). We discuss these differences in visual physiology in the context of the distinct foraging behaviours of the two species.

The relevance of goal directed movement for insect pest control

Efficient locomotion is a fundamental feature and requisite of all insects. Some insects, such as mosquito larvae, travel just a few centimetres, whereas others, such as Bogong moths, migrate over several hundreds of kilometers. Some insects traverse in air, others in water and some on ground. For goal-directed movement, irrespective of body size, the scale at which insects move, or the medium in which they travel, the principles of navigation remain the same. In this article, we discuss some of the visual navigational tasks that insects carry out and highlight the recent techniques developed to reconstruct visual information and track animals with exceptional accuracy. We emphasise the need to understand the visual ecology of insects and to adopt tracking tools and methods to control the movement and spread of insect pests.

Cathemerality: a key temporal niche

Given the marked variation in abiotic and biotic conditions between day and night, many species specialise their physical activity to being diurnal or nocturnal, and it was long thought that these strategies were commonly fairly fixed and invariant. The term 'cathemeral', was coined in 1987, when Tattersall noted activity in a Madagascan primate during the hours of both daylight and darkness. Initially thought to be rare, cathemerality is now known to be a quite widespread form of time partitioning amongst arthropods, fish, birds, and mammals. Herein we provide a synthesis of present understanding of cathemeral behaviour, arguing that it should routinely be included alongside diurnal and nocturnal strategies in schemes that distinguish and categorise species across taxa according to temporal niche. This synthesis is particularly timely because (i) the study of animal activity patterns is being revolutionised by new and improved technologies; (ii) it is becoming apparent that cathemerality covers a diverse range of obligate to facultative forms, each with their own common sets of functional traits, geographic ranges and evolutionary history; (iii) daytime and nighttime activity likely plays an important but currently neglected role in temporal niche partitioning and ecosystem functioning; and (iv) cathemerality may have an important role in the ability of species to adapt to human-mediated pressures.

Physiological properties of the visual system in the Green Weaver ant, Oecophylla smaragdina

The Green Weaver ants, Oecophylla smaragdina are iconic animals known for their extreme cooperative behaviour where they bridge gaps by linking to each other to build living chains. They are visually oriented animals, build chains towards closer targets, use celestial compass cues for navigation and are visual predators. Here, we describe their visual sensory capacity. The major workers of O. smaragdina have more ommatidia (804) in each eye compared to minor workers (508), but the facet diameters are comparable between both castes. We measured the impulse responses of the compound eye and found their response duration (42 ms) was similar to that seen in other slow-moving ants. We determined the flicker fusion frequency of the compound eye at the brightest light intensity to be 132 Hz, which is relatively fast for a walking insect suggesting the visual system is well suited for a diurnal lifestyle. Using pattern-electroretinography we identified the compound eye has a spatial resolving power of 0.5 cycles deg^-1 and reached peak contrast sensitivity of 2.9 (35% Michelson contrast threshold) at 0.05 cycles deg^-1. We discuss the relationship of spatial resolution and contrast sensitivity, with number of ommatidia and size of the lens.