Ballooning refers to the aerial displacement of spiders made possible by friction between rising air and strands of silk. The phenomenon is widespread in the order Araneae and is thought to be the primary means by which spiders disperse over long distances. Only recently have attempts been made to understand the aerodynamic constraints under which ballooning spiders must operate. The current study was stimulated by the cogent theoretical work of HUMPHREY (1987), and provides the first empirical data on the physical forces acting on spiders about to become airborne and on those that are already airborne. The data indicate (1) that both the silk and the spider's body provide the drag necessary for ballooning, (2) that fluid dynamic models overestimate the difficulty of becoming and remaining airborne, (3) that the spider has both postural and silk length control over drag development, (4) and that only very small spiders can rely on ballooning for dispersal over long distances.

Spiders vary enormously in their behaviour when placed on the surface of fresh water. In some families (e.g. Theridiidae), the spider typically becomes wet and either sinks or is incapacitated by adhesion to the water. In other families (e.g. Agelenidae), the spider remains dry and moves across the water using its legs in much the same way it does on land, with the members of each leg pair moving in alternation with each other. In at least one family (Pisauridae), the spider remains dry and moves across the water using a rowing or galloping gait in which the members of each propulsive pair of legs move in synchrony with each other. While some degree of hydrophobicity is widespread among spiders, the ability to move on water by rowing occurs rarely; it is common only among families in the Lycosoidea, which is a subset of the GST (Grate-Shaped Tapetum) clade. Our mapping of water surface locomotion behaviour of representatives of 42 families of spiders onto cladograms of the Araneae suggests that the ability to row evolved at the base of the clade that includes Trechaleidae, Pisauridae and Lycosidae and evolved independently in some members of the family Ctenidae. Rowing behaviour is seen in all subfamilies of Lycosidae but, unlike in the Pisauridae in which all animals tested showed the rowing behaviour, many individuals that could row did not do so all of the time. Among the 166 non-lycosoid species we have tested, we have found one species of Araneidae and two species of Salticidae that can row. It is evident from our data that, in most spiders, phylogeny trumps recent selection (based on habitat preference) in determining the spiders' locomotor behaviour on the water surface.

The vocal control system of oscine songbirds has some perplexing properties — e.g. laterality, adult neurogenesis, neuronal replacement — that are not predicted by common views of how vocal learning takes place. Similarly, the relation between the direct pathway for the control of learned song and the recursive pathway necessary for song learning is not understood. Some of the paradoxes of the vocal system of birds may disappear once the relation between the perception and production of learned vocalizations is better understood. To some extent, perception and production may be two closely related states of the same system.

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Three experiments were conducted to control for the effects of housing conditions during play deprivation on subsequent play rebound in periadolescent rats. To address play deprivation without the confound of social isolation, in Experiment 1, pairs of subjects were housed either in cages divided by wire mesh that allowed for olfactory, visual, auditory, and tactile interactions with a same-sex age-mate but prevented rough and tumble play or in standard cages. Running wheels were provided to similarly housed subjects in Experiment 2 to control for the ability to engage in physical activity. In Experiment 3, standard and brooder cages were used to control for the effects of housing area. Play-deprived subjects in all conditions showed a greatly increased number of play responses immediately following deprivation. The results from these experiments more clearly indicate that the absence of play is the crucial feature that brings about play rebound following deprivation.