Introduction Insects are overwhelmingly diverse ... so diverse you might well think it impossible to routinely recognize bugs, beetles and flies the way we expect at least a passing familiarity with most of the birds, mammals and other vertebrates that cross our paths. That perception is grounded in reality, since most known species of living things -- about a million of the 1.7 million or so named species -- are insects, and the number of insect species as yet undiscovered and unnamed undoubtedly runs into further millions. It all seems hopelessly overwhelming -- but it shouldn't. Insect diversity, especially the almost untapped diversity of little-studied insects such as tiny tropical flies, should be seen as a rich ore of insights to be mined for generations to come rather than as a barrier to the study of insect natural history today. In fact, most insects are relatively easy to identify to a meaningful level. The orders of insects -- the big groups such as flies, beetles, dragonflies and wasps -- are few and easy to learn, and most insect species (indeed, most animal species) belong to one of only four easily recognizable orders: flies (Diptera), wasps (Hymenoptera), beetles (Coleoptera) and moths and butterflies (Lepidoptera). These orders in turn are divided into families -- such as fireflies, mosquitoes and lady beetles -- most of which occur worldwide and are readily recognizable anywhere on the planet as variations on familiar themes. Many of the images in this book are from "exotic" places, but most should be easily recognizable as members of familiar families that probably occur in your own backyard, even though a disproportionate number of the species shown belong to rare families or families with unusually restricted distributions. Identification beyond the family level can be more difficult, and for many groups it has traditionally been the realm of specialists with microscopes, extensive libraries and reference collections. That is changing quickly; for more and more groups and more and more regions, identification right down to genus and species is getting easier, thanks largely to the digital revolution. If you know the family to which an insect belongs, you can make generalizations about how it lives and what it eats, but more detailed information about insect distribution and behavior is often tied to generic (genus) or specific (species) names. In general, insects from temperate countries do have species names, and you can find the names for the most commonly encountered or distinctive species by using recent photographic guides. Identification of tropical insects is more daunting because of the huge numbers of undocumented species and a lack of published identification guides. Even in the tropics, however, many of the large and more conspicuous groups are remarkably well-known, and commonly encountered species are often easily identifiable. By way of illustration, most of the Bolivian insects illustrated in this book were photographed while I was instructing at a field course in primary rainforest near the Peruvian border. We were able to identify most of the more conspicuous insects encountered during that course through the use of a small photographic guide called Amazon Insects (Castner, 2000) illustrated with about 160 photographs from the Peruvian Amazon. More remarkably, during less than two weeks in the Bolivian rainforest we encountered most of the insect groups illustrated by Castner. This is not to say that either the photos in Castner's book or the 300 or so neotropical insects illustrated here represent a significant proportion of the millions of insect species thought to occur in the Amazonian rainforest, but it does suggest that they represent a meaningful proportion of the distinct kinds of larger insects an ecotourist might encounter during a visit to the South American rainforest. Similarly, the 80 or so species illustrated here from Costa Rica hardly scratch the surface of the insect diversity of that hyperdiverse Central American country, but if you go bugwatching in Costa Rica you will probably find significant similarity between the species shown and discussed here and the insects you spot along forest trails and margins. The photographs in this book were identified partly by using reference collections, paper guides and websites, but many of the images were identifiable only with the help of specialists -- professional taxonomists who have identified hundreds of my specimens and images over the past several years. Some kinds of insects, as I have noted, are so poorly known that several of the images here are of undescribed (new) species photographed for the first time. A few of the photographs in this book are identified only to the family level because I could not identify them further, nor could I find a specialist able to identify them for me. An enormous amount of basic taxonomy remains to be completed before tropical insects will be covered by accessible identification tools like the wonderful guides now appearing for many groups of insects in temperate countries. Although this book will undoubtedly find use as a tool for identifying naturalists' digital images from bugwatching excursions near and far, it was not assembled as an identification guide, and it provides neither comprehensive coverage for any region nor balanced coverage across the Insecta. Instead, it is a compilation of images that illustrate insect diversity, form and function around the world. Most of the examples are drawn from the neotropics -- Earth's major cauldron of diversity -- but a few are from other areas, including Australia, New Zealand, temperate South America, the Pacific, the Caribbean and North America. Insect Distributions Since the images in this book were taken in lands scattered across half the planet, some comments on why which insects live where might be in order. If you check out the insects in your backyard or a city park, most of the species you encounter are likely to be secondarily widespread creatures that have travelled around the planet thanks to mankind's deliberate or accidental intervention. Ask a friend to name ten kinds of insects and I will bet that eight of them are European or Asian species that are now common in much of the world: European Earwigs, Cabbage White Butterflies, House Flies, most cockroaches, most crop pests, most common lady beetles, most common ground beetles, common hornets, yellowjackets and paper wasps -- the list goes on and on, as does the stream of new invaders arriving on foreign shores to displace native species. A few such invaders are included here, but most of the insects on the following pages were photographed in native ranges that still reflect the pre-human history of the planet, ranges that are Earth's collective memory of origins, expansions, divisions and contractions of habitats. Hundreds of millions of years of planetary change have divided, subdivided, recombined and divided species ranges again and again, driving speciation and generating the biodiversity that defines life on Earth today. When you look at a picture of an insect from an exotic place, try to think of where you have seen something similar. The odds are that the similarity you see reflects relationship, and that the insect belongs to a recognizable genus, a familiar family or at least a known order. At some point in the near or distant past that exotic insect shared a common ancestor with something you know. That bug from Cuba, for example, might have a very close relative in the American southeast, and those two species in turn might be very similar to a member of the same genus in northeastern North America. Related species are often similar because they resemble a common ancestor that was somehow subdivided -- perhaps by a barrier such as a mountain range or body of water -- into populations that evolved into different species. Professional taxonomists routinely plot phylogenies (like genealogies that show the relationship between species rather than individuals) of groups of related species against the geographic Excerpted from 500 Insects: A Visual Reference by Stephen A. Marshall All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.
