Chelicerates do not possess dedicated antennae like the Mandibulata but have evolved their second sets of appendages into the eponymous chelicerae. In scorpions, pectines are specialized comb-like structures, located on the ninth body segment, used for examining the substrate for chemo- and mechanosensory signals. The comb teeth, or pegs, are truncated beveled structures facing the substrate for probing, and are studded with numerous sensory receptors. Afferents from the pectines project into a distinct neuropil of the central nervous system, located behind the fourth walking leg neuropils. Denise Drozd analyzes afferents of single pegs in Mesobuthus eupeus by backfilling, combined with immunohistological labeling of neuropil regions. Her results suggest a topographic representation of the chemosensory fibers within the pectine neuropil instead of the typical chemotopic representation.

More than two thirds of all living organisms described to date belong to the phylum Arthropoda. But their diversity, as measured in terms of species number, is also accompanied by an amazing disparity in terms of body form, developmental processes, and adaptations to every inhabitable place on Earth, from the deepest marine abysses to the earth surface and the air. The Arthropoda also include one of the most fashionable and extensively studied of all model organisms, the fruit-fly, whose name is not only linked forever to Mendelian and population genetics, but has more recently come back to centre stage as one of the most important and more extensively investigated models in developmental genetics. This approach has completely changed our appreciation of some of the most characteristic traits of arthropods as are the origin and evolution of segments, their regional and individual specialization, and the origin and evolution of the appendages. At approximately the same time as developmental genetics was eventually turning into the major agent in the birth of evolutionary developmental biology (evo-devo), molecular phylogenetics was challenging the traditional views on arthropod phylogeny, including the relationships among the four major groups: insects, crustaceans, myriapods, and chelicerates. In the meantime, palaeontology was revealing an amazing number of extinct forms that on the one side have contributed to a radical revisitation of arthropod phylogeny, but on the other have provided evidence of a previously unexpected disparity of arthropod and arthropod-like forms that often challenge a clear-cut delimitation of the phylum.

JOHN G. HILDEBRAND Research on insect olfaction is important for at least two reasons. First, the olfactory systems of insects and their arthropod kin are experi mentally favourable models for studies aimed at learning about general principles of olfaction that apply to vertebrates and invertebrates alike. Detailed comparisons between the olfactory pathways in vertebrates and insects have revealed striking similarities of functional organisation, physiol ogy, and development, suggesting that olfactory information is processed through neural mechanisms more similar than different in these evolution arily remote creatures. Second, insect olfaction itself is important because of the economic and medical impact of insects that are agricultural pests and disease vectors, as well as positive impact of beneficial species, such as the bees and moths responsible for pollination and production of honey. The harm or benefit attributable to an insect is a function of what it does - that is, of its behaviour - which is shaped by sensory information. Often olfaction is the key modality for control of basic insect behaviour, such as ori entation and movement toward, and interactions with, potential mates, appro priate sites for oviposition, and sources of food. Not surprisingly, therefore, much work on insect olfaction has been motivated by long-term hopes of using knowledge of this pivotal sensory system to design strategies for mon itoring and managing harmful species and fostering the welfare of beneficial ones.

Whip spiders (Amblypygi) can be large and terrifying animals with strong, raptorial pedipalps and long antenniform first legs that can produce a span of as much as 60 cm. Others are small and scarcely span 5 cm. They all lead a secretive nocturnal life and are extremely dangerous to other arthropods and small vertebrates. In contrast to spiders and scorpions, they are of no commercial, economic or medical importance and they are difficult to study in the field because of their nocturnal habits, possible reasons why they have been greatly neglected until recently, by scientists and naturalists. Whip spiders represent an old group that dates back to the Carboniferous period. Their partly primitive and partly derived morphological characters and habits make the study of these animals interesting, while observation of their behaviour greatly increases our knowledge and understanding of arachnids in general. In this book the author describes their morphology and systematics, their life history, their fascinating sensory biology, their complex mating dances and reproductive biology, and their ecology and distribution. Thus he has made a significant contibution to a better understanding of the morphology and biology of the Arachnida as a whole. Whip Spiders is an outstanding contribution to science and it will be of interest for anyone with an interest in Arachnida and for those keeping and breeding spiders.

Insects are among the most diverse and adaptable organisms on Earth. They have long been our chief competitors for food and are responsible for spreading devastating afflictions such as malaria and encephalitis. The insects' ability to thrive is due in large part to their well-developed sensory systems, which present a host of novel physiological,

Homing phenomena must be considered an important aspect of animal behaviour on account of their frequent occurrence, their survival value, and the variety of the mechanisms involved. Many species regularly rely on their ability to home or reach other familiar sites, but how they manage to do this is often uncertain. In many cases the goal is attained in the absence of any sensory contact, by mechanisms of indirect orientation whose complexity and sophistication have for a long time challenged the skill and patience of many researchers. A series of problems of increasing difficulty have to be overcome; researchers have to discover the nature of orienting cues, the sensory windows involved, the role of inherited and acquired information, and, eventually, how the central mechanisms process information and control motory responses. Naturally, this book emphasizes targets achieved rather than areas unexplored and mysteries unsolved. Even so, the reader will quickly realize that our knowledge of phenomena and mechanisms has progressed to different degrees in different animal groups, ranging from the mere description of homing behaviour to a satisfactory insight into some underlying mechanisms. In the last few dacades there have been promising developments in the study of animal homing, since new approaches have been tried out, and new species and groups have been investigated. Despite this, homing phenomena have not recently been the object of exhaustive reviews and there is a tendency for them to be neglected in general treatises on animal behaviour.

My initial interest in the Solifugae (camel-spiders) stems from an incident that occurred in the summer of 1986. I was studying the behavioral ecology of spider wasps of the genus Pepsis and their interactions with their large theraphosid (tarantula) spider hosts, in the Chihuahuan Desert near Big Bend National Park, Texas. I was monitoring a particular tarantula burrow one night when I noticed the resident female crawl up into the burrow entrance. Hoping to take some photographs of prey capture, I placed a cricket near the entrance and waited for the spider to pounce. Suddenly, out of the comer of my eye appeared a large, rapidly moving yellowish form which siezed the cricket and quickly ran off with it until it disappeared beneath a nearby mesquite bush. So suddenly and quickly had the sequence of events occurred, that I found myself momentarily startled. With the aid of a headlamp I soon located the intruder, a solifuge, who was already busy at work macerating the insect with its large chelicerae (jaws). When I attempted to nudge it with the edge of my forceps, it quickly moved to another location beneath the bush. When I repeated this maneuver, the solifuge dropped the cricket and lunged at the forceps, gripping them tightly in its jaws, refusing to release them until they were forcefully pulled away.