Preface This book is based on material originally gathered in support of a third-year entomology course -- "The Natural History of Insects" -- that I started teaching at University of Guelph in 1982. The text is based on the lecture notes for that course, the picture keys are based on the course manual and the photographs are part of a collection that was initiated to provide color to my lectures in several entomology courses over the past 20 years. The text sections in this book provide an introduction to insect diversity and natural history, with basic information about all major insect families. The photos and captions provide a visual overview of the diversity of each family with discussions of common or especially interesting genera and species. Picture keys are provided to the orders and common families of most orders. The emphasis is on northeastern North America, loosely interpreted as anything east of the Mississippi River and north of the state of Georgia. Insect identification Although the focus of this book is on the common families of northeastern North American insects, the keys and photos should be useful for identifying orders and most families anywhere in the world. If you are trying to identify an insect to order, start with the illustrated keys (pages 615-666). When you think you have a match, turn to the appropriate section of the book and look over the full spectrum of photos for that order. If you know the order and want to identify your insect to the family level you can either jump right to the photos and captions, or start with the illustrated keys. The illustrated keys may not take you right to the family level, but they will guide you to the correct part of the book to look for further information. The photos and captions themselves should serve as a practical field guide to the family or subfamily level for common insects from anywhere in North America, and will serve for positive identification of some eastern insects at the genus or species level. Almost all the photographs are of northeastern species, although a few interesting groups that do not occur in the east (honey ants, pollen wasps) were slipped in for interest, and a few groups are illustrated with photos from outside North America, as noted. The great majority of the photographs were taken in Ontario, Canada (mostly the Bruce Peninsula or southern Ontario), but a few are from Mountain Lake Biological Station, Virginia (where I teach a field entomology course), and elsewhere in the eastern United States. The illustrated family keys are designed to be as user-friendly as possible, with an emphasis on characteristics visible to the naked eye or easily discernable with a handheld magnifying glass. Most keys represent a compromise between ease of use and comprehensiveness. The keys in this book lean towards ease of use and should be treated as shortcuts rather than definitive roadmaps. The keys to families in the larger orders (Diptera, Hymenoptera, Coleoptera) are designed to aid in the identification of typical members of commonly encountered families, and the odd rarity or exception will not key out. Comprehensive keys to the families of these orders are listed in the references, but most require experience, patience and a good microscope to use. For example, the key to families of beetles in American Beetles (Arnett et al., 2002) is 185 complex couplets long; the key to families of flies in the Manual of North American Diptera (McAlpine et al., 1981) is 152 couplets long. Those keys will work for almost all North American beetles and flies; the simplified keys in this book will probably work for over 95 percent, including almost all routinely encountered taxa. I think it is a good compromise, but it is a compromise, and the serious student will want to check problematic identifications using more technical literature. The "id" and "idae" of entomological jargon This book is organized around insect orders and families. Names given to orders (big groups, like beetles and flies) do not have standard endings, but orders are divided into families, and the names of families always end in "-idae." Insect families are routinely mentioned by informally contracting the family name to end with "-id." Ground beetles, for example, are formally called the family Carabidae, but are informally referred to as "carabids." Sometimes it is useful to talk about a number of related families together, in which case we talk about superfamilies and the names always end in "-oidea." Some families, especially large families like the leaf beetles (Chrysomelidae), are usefully divided into subgroups called subfamilies (subfamily names end in "-inae"). The scientific name of a species always has two parts, the genus (always capitalized and in italics) and species (always in italics, never capitalized). For example, the Monarch Butterfly ( Danaus plexippus ) is a nymphalid butterfly in the family Nymphalidae and the subfamily Danainae. In scientific papers (but not in this book) the name of a species is usually followed by the name of the person who first described and named it (in parentheses if it was first described in another genus). The Monarch, then, would appear as Danaus plexippus (L.), with L. serving as a short form for its "discoverer" Linnaeus. Taxonomic hierarchy and corresponding suffix Superfamily: -oidea Family (formal): -idae Family (informal): -id Subfamily: -inae Many insect species, especially large or economically important species, have common names like the Monarch, but most do not. Where widely used common names exist they are included here. Common names are normally capitalized. Family names appear in bold face when they first appear in the text. Classifications are in constant flux as we discover more about the relationships between groups of organisms, and the names used in this book may be different from those you are already familiar with. I have taken a conservative approach to higher classification, using the family concepts in current usage unless there are compelling reasons to accept a recent change. Significant changes are indicated in the text and captions, and generally follow a recent checklist, catalogue or monograph in the Selected References section at the back of this book. An Overview of Six-legged Life We live in a world of insects. They are our continual and closest neighbors, so much a part of day-to-day life that most of us hardly take notice of them unless they are particularly loud or obnoxious, or they stand accused of robbery or assault. It is easy to forget that human beings form a tiny two-legged minority in an overwhelmingly six-legged world -- a world where a bit of knowledge about our dominant neighbors can unlock the door to a surprisingly diverse local environment. The key to seeing and understanding insect diversity is knowledge of the common orders and families of insects. Armed with that knowledge, a sizeable proportion of the multitude of walking, crawling and flying creatures you share your daily life with will become familiar neighbors, replete with predictable habits. Insects are influential and interesting creatures well worth getting to know. It is self-evident that you can hardly step outdoors without exposure to a usually ignored infinity of insect types, but surprisingly few people are aware that these ubiquitous animals make up the staggering majority of all living things. Most named species of living things, including close to eighty percent of the approximately one and a half million named animal species, are insects. These numbers would be all the more impressive if they took into account the millions of insect species still awaiting discovery and formal naming. We can only guess that the total number of insect species is somewhere between five and ten million, and we have only the crudest idea of how many individual insects there are. According to one estimate, there are about 200,000 ants for every living human being, and we can safely assume that each of us is also matched by many thousand flies, fleas, bugs and beetles. Perhaps you are a practical person, unimpressed by raw numbers and the mere fact that insects are the overwhelmingly dominant inhabitants of our planet. You might still find it worthwhile to gain some insight into a group of organisms that bite, carry diseases, cost us billions of dollars every year in crop losses and lead us to contaminate our environment with a frightening variety of toxic chemicals in our attempts to get the better of them. Insect-borne diseases, like plague and typhus, have periodically wiped out sizable portions of the Earth's human population, and have repeatedly turned the tides of war by killing far more people than guns and swords. Even today, half the world's population is at risk from mosquito-borne malaria, and another 90 million people in 76 countries suffer from insect-borne filariasis. Chagas' disease, caused by a bug-borne protozoan, affects another 16 million to 18 million people in South and Central America, and countless millions are affected daily by fly-borne food and water contamination. -- Introduction If insects are worth getting to know as an enemy of humankind, they are even more worthy of attention as our benefactors. We could probably get by without insect products such as honey and silk, but our food production systems would be wholly changed in the absence of insect pollinators, and entire ecosystems would collapse if there were no insects in the food chain. Furthermore, insect predators and parasitoids keep pest insect numbers down, plant-eating insects regulate plant density, and microbe-eating insects, such as maggots, regulate the decomposition phase that every living thing must go through. Although our history, health and finances all pivot to a surprising degree on insects, the best reasons to be interested in insects lie elsewhere. One of the great appeals of these invertebrates is their remarkable combination of seemingly infinite variety with comforting predictability. Insects as a whole, and each of the major subgroups, exhibit several constant and predictive attributes despite their dazzling array of novelties and remarkable modifications. Therefore, one can easily learn to recognize the major insect groups and their basic biology, and make safe generalizations about most of the insects encountered day to day. At the same time, it is always possible to find new things. Even after decades as a professional entomologist, I frequently come across insects I've never seen before or watch insects doing something new and remarkable to me, perhaps something I've read about with interest, or perhaps something never previously observed. Entomology -- the study of insects -- is both an absorbing hobby and a scientific frontier we can push forward through backyard observations. I hope that the following overview of insect diversity and natural history will provide both an introduction to the science of entomology, and a framework for the observation and appreciation of the small life that surrounds us all. What is an insect? Just what is an insect anyhow? To put that question in perspective, think of a tree representing all animal life. Make it a huge old tree with a bunch of spindly twigs growing off the lower part of its massive trunk. Those little branches represent relatively small groups such as sponges, the sea cucumber lineage, the vertebrate lineage, and the mollusk and worm lineage. The main tree trunk, above those spindly twigs, is made up entirely of animals that periodically shed their skins to allow growth (Ecdysozoa). These moulting animals include the nematodes and their relatives as well as a few very small groups such as the penis worms, but most Ecdysozoa, including around 90 percent of all animal species, belong to the phylum Arthropoda. Arthropods can be thought of as "inside out" relative to vertebrates because their skeleton is an external shell. The term "arthropod" means "jointed feet," and refers to a conspicuous side-effect of having a hard external shell. Jointed appendages were an inevitable attribute for knights in armor, and the same goes for invertebrates with a hardened, or sclerotized, external skeleton. The phylum Arthropoda is divided into several classes, including the arachnids (spiders and their relatives), myriapods (millipedes, centipedes and their relatives), crustaceans (crabs and their relatives), and insects. The class Insecta, which includes the overwhelming majority of all arthropod species, is defined by several unique attributes which might explain why insects are so successful. The most obvious of those attributes, and one reflected in the name "insect," is the division of the body into three sections: the head, thorax and abdomen. It is useful to think of insects as a group in which different parts of the body were assigned different tasks, and given appropriate appendages for each those different tasks. The insect head is the result of the first few body appendages getting the jobs of scouting out the environment and handling food. In the basic insect body plan, the part of the head in front of the mouth has a pair of sensory antennae followed by an upper lip, or labrum. The appendages immediately behind the mouth are modified into unsegmented jaws called mandibles. A pair of food-handling and sensory appendages called maxillae follows the mandibles, and the maxillae are followed by a similar pair of appendages fused in the middle to form a lower lip, or labium. Both the maxillae and labium have distinctive segmented processes, called palpi (or palps). Many insects, such as grasshoppers, cockroaches and beetles, retain simple chewing mouthparts in which you can easily examine these basic bits and pieces, but in some groups of insects, the mouthparts are strongly modified. It helps to be familiar with simple chewing mouthparts, like those in grasshoppers, in order to appreciate how the specialized mouthparts of butterflies, bugs, mosquitoes and many other groups can be derived by simple modification of those basic oral appendages. The second of the insect's three body sections is the thorax, which is usually a big muscle-packed box made up of three segments, each with appendages that have become specialized for locomotion. The thorax is the insect's transportation center, almost always bearing three pairs of legs and usually with two pairs of wings. Insects with wings make up not only the majority of the class Insecta, they make up the majority of all animals. The third insect section is the abdomen, essentially a segmented sack of digestive and reproductive organs, usually devoid of any conspicuous appendages other than those involved with sex or laying eggs. Even a wasp's stinger, quite a conspicuous structure at times, is really just a modified egg-laying tube derived from appendages at the end of the abdomen. Grasshoppers are great insects for a quick and casual study of insect parts, and you should have no problem getting your hands on one of these common insects. The grasshopper's body segments should be readily apparent once you realize that the wings usually project from the thorax right back over the abdomen. You might start by looking at the head appendages -- this is easily done, as the big, triangular, chewing mandibles make it easy to get your bearings on the other mouthparts. Don't worry about the brown saliva (we called it tobacco juice when I was a kid) that living grasshoppers dribble over your probing fingers, just wipe it off and take note of the two pairs of segmented palpi following the mandibles. The first palpi arise from the maxillae; the second ones come off the labium. Now, hold your grasshopper by the hard section just behind the head. This section is hard because its top and sides are enveloped by a big shield made from the top of the first of the three thoracic segments. The second and third thoracic segments both support wings, but the straight-edged, somewhat leathery forewings usually conceal the hind wings. By grasping a forewing and gently pulling it away from the body, you will expose the large, fanlike hind wing. Now that you have checked out your hopper's wings, look closely at the sides of the abdomen for the abdominal spiracles, which look like a series of portholes. The spiracles, also found on the side of the thorax, open into a system of breathing tubes which form an air delivery system reminiscent of our own system of blood vessels and capillaries. Insects don't have blood vessels like ours, and insect blood, more properly called haemolymph, isn't used for respiration like we use blood. Insect blood, which fills the body cavity, serves a variety of other roles ranging from internal transport of nutrients and chemical messengers through to hydraulic operation of various body parts. Insect blood does circulate, but it isn't restricted to vessels like vertebrate blood. Your grasshopper even has a heart of sorts, really just a perforated dorsal tube that pumps to circulate the blood toward the head. In a way, insects are not only "inside out" relative to those of us supported by internal skeletons, but they are also "upside down" because the pumping organ is not in a ventral (lower) position like the human heart, but in the dorsal (upper) position like the human spinal cord. The insect equivalent of a spinal cord is a nerve cord running along the ventral part of the body cavity. The insect nerve cord loops up around the esophagus to form a brain of sorts, in the form of a concentration of nervous tissue in the head. When I suggested that you pick up a grasshopper to browse the major insect bits, I was making the safe assumption that most people know what a grasshopper is. In the following chapters, I will discuss hexapod highlights in the context of specific insect groups, starting with some primitive wingless types and moving up the evolutionary tree to ultimately arrive at a sort of insect treetop, somewhere among the ants, wasps and bees. The winged insect orders comprise the mainstream of insect evolution. Most of this book goes with that flow, but chapter one dabbles in some of the interesting little trickles of six-legged life that ultimately give rise to the torrent of flying insects that inundate the planet, and chapter 13 leaves the hexapods for a quick look at some other arthropod orders. Excerpted from Insects: Their Natural History and Diversity: With a Photographic Guide to Insects of Eastern North America 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.
