Monday, March 26, 2018

Speaker Report - Robert Whyte on Spider Mania

(Report by Glenda Walter)

Robert Whyte was a relaxed, entertaining and informative speaker on the subject of his favourite creatures, spiders. Ten years ago, he was studying habitat regeneration, and decided to use spiders as a measure of success. His first small study showed that five times the number of spiders (abundance) and many times the number of species, genera and families (diversity) inhabited original remnant vegetation compared to that in a degraded area. He then conducted a second study, using 400 square metre sites of:
a) a suburban garden with native creek-side plantings
b) an area which had undergone five or six years of regenerative work and
c) preserved original vegetation.
This gave the same results, showing greater abundance and diversity in natural good-quality bushland. The garden had the fewest number of genera, species and spiders overall while there were more in the restored area, and most by far in the un-degraded site. Spiders are mid-level predators and rely on other invertebrates as prey. They flourish where there is plant and insect diversity. Therefore, high spider abundance and diversity are good indicators of habitat health.
By this time Rob was hooked and became interested in spiders for their own sakes. Having seen excellent publications with wonderful photographs on spiders in Korea and Japan, he and Greg Anderson decided that they would co-author a book on Australian spiders. Many years later, this book, “A Field Guide to Spiders of Australia”, was published by CSIRO in 2017 and has been widely acclaimed. Well over 1000 photographs, simple and interesting text, a comprehensive index and excellent layout make this book one of the best field guides I have seen.
Spider taxonomy has been somewhat neglected in the southern hemisphere until comparatively recently when resident Australian arachnologists have been examining live populations and using modern technology to sort and rename them. In the Hersiliidae family (Two-tailed Spiders) for example which 20 years ago contained five Australian members, about 50 are now recognised. Robert and his partner Anne showed us large and dramatic images to illustrate some spiders both large and small, and spoke about some spider myths and amazing facts.
  • ·         White-tailed spiders, Lamponidae family, are not dangerously venomous and do not cause ulcerating wounds.
  • ·         Wolf spiders, family Lycosidae, are excellent mothers, carrying their newly-hatched children on their backs for several weeks to protect them.
  • ·         The most dangerous Australian spiders are the “Huntsman Spiders” (Sparassidae), not because they bite, but because accidents are caused when they startle people.
  • ·         Deinopis subrufa, the net-casting spider seen around Toowoomba and elsewhere, has eyes which are 2000 times as sensitive as those of humans. The light sensitive membrane inside their eyes is dissolved at around daylight, and renewed at dark, so that their eyes are not damaged by bright sunlight and the spider is able to hunt its prey in the dark.
  • ·         Spiders can’t hold their breath, and can’t “bark” or “call” as they have no vocal cords, but some species produce sound by stridulation, scraping parts of their bodies together as crickets do.
  • ·         Some “bird-dropping” spiders not only look like bird poo, but also smell like it!
  • ·        Various ant-mimicking spiders in the Salticidae family look similar to ants, and produce pheromones which convince ants that they are family members, allowing the spiders to live with them and feed on their larvae.
  • ·         Habronestes bradleyi, a member of the ant-eating Zodariidae family, has smell receptors in its “armpits”, allowing it to sense wounded or straggler ants.

·         Robert showed several images of tiny but beautiful male peacock spiders in the Salticidae family (Jumping Spiders) which dance to display to possible mates, spreading coloured body flaps and fringes and raising their third pairs of legs. Each species has a different colour pattern and display.
Spiders are millions of years older than insects and now predate them massively, globally consuming as much food daily as humans. Because many are very small, they are often overlooked. Instead of the four thousand plus species now known, scientists expect that in reality there are probably closer to 20,000 species. So, keep looking, Field Nats, it is likely that you may find undescribed species in your own backyards! A big thank-you to Robert Whyte and Anne for their enthralling presentation.

Robert Whyte, co-author of A Field Guide to Spiders of Australia, CSIRO Publishing 2017

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