Our friends in very low places

As I travel in the tropics, I have often thought that the fascinating insects and other small creatures that I encounter have been much neglected by authors and film-makers. There has been a tendency to focus on large, charismatic furry animals rather than the source of true diversity, the invertebrates. Conservation activities have also been largely based on the interest in large beasts. Insects are, after all, the most diverse group of animals on our planet and, as Piotr Naskrecki states:

"From pollination to seed dispersal, from soil production to waste removal and from water filtering to being food for others, invertebrates make Earth a liveable planet."

It is refreshing to have two new books about the "smaller majority" by two naturalists whose enthusiasm for these creatures abounds throughout the texts. Both authors show how from early childhood they became interested in the living world; one would become an insect taxonomist and conservationist and the other, the greatest modern interpreter of natural history.

David Attenborough confines his text entirely to the invertebrates, whereas Naskrecki includes some of the smaller vertebrates, such as frogs, amphibians and lizards. But they must be small to qualify and so, for example, only the smallest of the Madagascan chameleons are included.

Attenborough's book was written to accompany a television series of the same name, and it contains more text and more unusual and interesting insect facts than Naskrecki's book, which has many more well-annotated, close-up photographs.

Naskrecki confines himself to tropical animals and divides the book into three main chapters on tropical humid forests, savannas and deserts. He has obviously travelled to many different places in the tropics as there is worldwide coverage. The forest chapter occupies two thirds of the text, which is hardly surprising considering the huge insect diversity of tropical forests. It is good to read something about the smaller residents of tropical savannas rather than just the big five animals that feature in so many places, although even Naskrecki cannot help but include a photo of elephants when he describes the insect diversity to be found in an elephant's footprint.

Attenborough includes many familiar invertebrates from the temperate regions such as slugs, snails, woodlice and mayflies. There is inevitably some repetition of facts between the two books because they largely cover the same organisms such as crabs, spiders, scorpions, grasshoppers, ants, bees and many other animals. They both also explain the various theories of why the tropical rainforest is so diverse without choosing one theory as the most probable.

The Attenborough text delves more into the evolutionary history of the invertebrates and frequently illustrates and discusses fossils, a favourite subject of the author. The first chapter about the emergence of animals on to land more than 400 million years ago and the detailed description of horseshoe crabs is completely different from anything in Naskrecki's book.

The second chapter is about the evolution of flight in insects, from that of huge fossil dragonflies to present-day insects. There is also a lot more about the fascinating and often bizarre sex life of the invertebrates from Attenborough. It is amazing how many different ways insects have evolved to transfer the sperm from male to female, a dangerous process in some species of spiders and mantids where the female eats the male after the sexual act has taken place.

Naskrecki also dwells on reproduction in several places. Velvet worms stand out among other animals for their varied modes of reproduction. The simplest way is the deposition of a spermatophore directly on the female's skin, which dissolves underneath and allows the sperm to enter her body to find its way to her ovaries. In some species, the male deposits sperm on top of the female's head, and in others the male puts his head into the female's genital opening at the rear end of her body to deliver his sperm.

I found Attenborough's third chapter on "Silk makers" the most fascinating.

Many different types of insect produce silk, varying from the silk-wrapped larvae of the silkworm to the enormous variety of webs and types of silk produced by spiders. The contrivances with which spiders catch insects are varied and devious. One species swings a weighted thread around its victim in the same way that a South American cowboy swings a bolus to catch his cows. Naskrecki is a specialist on the taxonomy of katydids and so the discussion and photographs of these insects are particularly good.

Both authors are excellent writers and have produced most readable texts.

Attenborough, as usual, has a wonderful way of making analogies to get his point over. For example, the complicated way in which beetle wings are folded under the elytra is described as folding like the work of a Japanese master of origami. He also dwells a lot more on some of the less popular categories of invertebrates such as slugs, snails, woodlice and centipedes.

Both books devote considerable space to the many ways to avoid predators. There are stunning photos of insect camouflage: spiders that exactly match the colour of orchid flowers; the cryptic colouring of many moths; insects that resemble sticks; and others with transparent wings that allow them to blend perfectly into their background. On the other hand, there are brightly coloured insects that advertise the fact that they are poisonous or unpleasant tasting. These often have non-poisonous mimics that have very similar patterns and derive the benefit of avoidance by predators without having to produce the unpleasant chemicals.

These wonders of evolution are ideal subjects for photographic books.

Although both of these have fascinating texts, they are really photo essays. They are splendidly illustrated with copious spectacular photographs. In the case of Naskrecki, the photographs were all taken by the author in the natural habitats of all the animals and are particularly fine (as shown here). At the end of the book, he includes a short chapter on how to photograph small creatures, which will be useful to any nature photographer setting out for the tropics for the first time. The modern developments in close-up photography have been exploited well.

A strong conservation message comes through since both authors intersperse their texts with concern about the loss of species, extinctions and the need for more conservation efforts worldwide. Both authors have consulted a wide range of specialist taxonomists so that the nomenclature they use is accurate.

The Attenborough book is a more organised walk through the diversity of invertebrates, and the Naskrecki book is more of an account of the incredible variety of insects that he has encountered during his extensive travels in the tropics. What I particularly like about both books is that they contain so much captivating data on insect behaviour. They brought back many happy memories of numerous small creatures encountered in the rainforests of the world: the pollinators, seed dispersers, defenders and predators of the plants I study.

If you are travelling to the tropics and can afford only one of these splendid works, Naskrecki's book is the more useful. If you want to put your feet up at home and learn many fascinating insect facts, then the Attenborough book is for you. But the books are sufficiently different to merit the purchase of both. You do not need to be an insect specialist to enjoy them - they are written to encourage more people to appreciate the wonders of insect diversity.

I do hope some of today's children will be inspired to become naturalists of the calibre of these authors as they read these books and watch the wonderful films on which the Attenborough text is based. I also hope that reading the books will cause people to appreciate insects more and to regard them not just as noxious, stinging or disease-carrying creatures.

Insects and other invertebrates are a vital and wonderful part of nature.

Sir Ghillean Prance is former director of the Royal Botanic Gardens, Kew, and scientific director of the Eden Project.

30 Biological SciencesThe Times HigherJApril 21J2006