Temporal acuity of honeybee vision: behavioural studies using flickering stimuli

ABSTRACT. Temporal resolution of freely-flying bees was measured by training bees, Apis mellifera (Linn.), to discriminate between a steady light and a flickering light. Two kinds of experiments were conducted: those using a homochromatic flicker, in which the intensity of the flickering light varied periodically with time; and ones using a heterochromatic flicker, in which the colour of the flickering light varied periodically. In either case, the time-averaged properties (intensity and colour) of the flickering light matched those of the steady light, and the bees' ability to discriminate between the two stimuli was measured for various flicker frequencies. The results indicate that bees perform poorly in the homochromatic flicker experiments, regardless of the colour of the light (u.v., blue or green), but well in those with heterochromatic flicker. Heterochromatic flicker experiments using various pairwise combinations of the colours U.V., blue and green (corresponding to the three known spectral receptor-types in the bee's retina) reveal that temporal resolution is much better when blue is one of the component colours, than when it is not. The simplest interpretation of the results is in terms of colour channels possessing different response speeds. Heterochromatic flicker promises to be a useful tool in investigating the temporal properties of colour vision in bees.     

Burrowing of the lingulid brachiopod Glottidia pyramidata: its ecologic and paleoecologic significance

Contrary to popular assumption, the pedicle of Glottidia is not its principal burrowing organ. The brachiopod props itself up with the pedicle and enters the sediment with the valves leading, anterior end first. The pedicle trails behind. Burrowing is accomplished by cyclical valve motions: rotary, sliding, and gaping movements are used. Rapid valve closure ejects water from the mantle cavity to loosen the sediment. The lateral setae convey mucus-bound sand posteriorly (upwards). X-radiography shows that the burrows are U-shaped: in a few hours, the animal reappears in feeding position with the anterior end pointing out of the sediment and the pedicle extending down into the burrow. This burrowing process explains the substrate preferences of lingulids. The thick. closely spaced setae are adapted for burrowing. The spacing between individuals is increased, suggesting competition for food.     

Effects of Severe Tropical Cyclone Larry on rainforest vegetation and understorey microclimate near a road,powerline and stream

Abstract Severe Tropical Cyclone Larry damaged a large swathe of rainforest to the west of Innisfail in north‐eastern Queensland on 20 March 2006. Within the path of the most destructive core of the cyclone were sites previously established along human‐made (powerlines and highways) and natural (streams) linear canopy openings for a study of edge effects on adjacent rainforest plant communities and associated microclimates. Vegetation damage and understorey microclimate parameters were measured 6 months after the passage of Cyclone Larry and compared with results before the cyclone. We examined the spatial patterns of vegetation damage in relation to natural and artificial linear clearing edges and the vegetation structural factors influencing these patterns as well as resulting alterations to microclimate regimes experienced in the rainforest understorey. Vegetation damage was spatially patchy and not elevated near linear clearing edges relative to the forest interior and did not differ between edge types. Vegetation damage was influenced, albeit relatively weakly, by structural traits of individual trees and saplings, especially size (diameter at breast height, d.b.h.) and successional status: tree damage was greater in pioneer species and in larger trees, while sapling damage was greater in canopy tree species than in understorey tree or shrub species. Changes in the understorey microclimate mirrored the degree of damage to vegetation. Where vegetation damage appeared greater, the understorey microclimate was brighter, warmer, drier and windier than below less‐damaged areas of the forest canopy. Overall, understorey light availability, wind speed and the diurnal ranges of air temperature and vapour pressure deficit increased dramatically after Cyclone Larry, while pre‐cyclone edge gradients in light availability were lost and temperature and vapour pressure deficit gradients were reversed.     

Changing conditions and conservation at Ashton Wold, the birthplace of the SPNR

N. C. Rothschild who founded the Society for the Promotion of Nature Reserves, stressed the importance of conserving specific habitats–especially those with no exact counterpart on the European mainland–and making surveys of such areas worthy of conservation. He also stressed the importance of the management of existing reserves. Owing to the conditions which pertained during World War II the area at Ashton Wold, subsequently declared a Site of Special Scientific Interest, lacked management for several years. The open spaces in the woodland became overgrown, the tree cover increased, drainage declined and the change which took place in the fauna and flora illustrated the need for enlightened management. The re-creation and creation of nature reserves and flowering grassland at Ashton are discussed.     

Aide memoire mimicry*

Abstract. 1. Animals and plants may gain protection by reminding would-be aggressors of failure, or an unpleasant experience following an attempt at capture and ingestion. Thus they need not be mistaken for noxious or dangerous prey; defence is adequate if the aggressor is forced to recall the attributes of such species, or the disagreeable sequela to a previous assault upon them. 2. Batesian mimics and mildly toxic Mullerian mimics can also add to their repertoire by such defensive strategies. 3. Several examples of this phenomenon, designated aide mémoire mimicry, are described.     

The biological roles of pyrazines: evidence for a warning odour function

Recently it has been shown that pyrazines are associated with many aposematic, chemically defended insects. We have demonstrated that naive hatchling chicks, when offered drinking water to which 2-methoxy-3-isobutylpyrazine is added, develop a neophobic 'alerting' reaction. The birds are not only capable of forming a conditioned aversion to the pyrazine when it is paired with quinine sulphate but they can also detect it from a distance probably by olfaction. This suggests that birds, a major group of insect predators, can interpret pyrazines as alerting or warning signals. The relationship of pyrazines with other alerting signals, and their evocative qualities are discussed.     

Reactions of various predators to insects storing heart poisons (cardiac glycosides) in their tissues

Notes are given of experiments in which mammals and birds were fed with insects which sequester and store cardiac glycosides, and the insensi-tivity of the quail (Coturnix japonicus Tern.) to these substances is recorded. The variation in predators' reactions to toxic insects is discussed.     

Carotenoids and bile pigments in Danaid and swallowtail butterflies

The carotenoids found in adult kite swallowtails ( Graphium spp.) and the Danaid glassy tigers ( Ideopsis, Tirumala and Parantica ), butterflies with exposed blue/green pigmented wing membranes (which contain pterobilins) and a modified scale vestiture, were compared with those of related species of Papilios and Danaids with concealed wing membranes an an entire scale vestiture. It was found that both the kite swallowtails contained only lutein, and even lacked β-carotene, the first known instance among butterflies. This was presumably due to selective storage by the larva since the food-plant was found to be rich in varied carotenoids. A possible link between the high concentration of pterobilins in the wing membrane and the lack of carotenoids is discussed.