Library of Congress Cataloging-in-Publication Data

Introduction

Invertebrates rule the earth.  Despite the attention given to the backboned vertebrates—the fish, amphibians, reptiles, birds and mammals—it is the invertebrates, animals without backbones, which have always dominated life on our planet.  Invertebrate animals have flourished in every possible ecological niche, from the deepest depths of the oceans to the thinnest mountain air, from sweltering deserts to steaming jungles to freezing polar regions.  Of the 26 major groups of animals, known as “phyla”, all but one consists solely of invertebrates.  Of all the animals known to science, over 99% are species without backbones.          

Today, invertebrates such as scorpions, millipedes, centipedes and tropical cockroaches make up one of the fastest-growing sections of the exotic pet trade.  A wide variety of species are now inexpensively available from breeders, dealers and pet shops.  So if you are looking for a fascinating pet that is unusual, easy to care for, doesn’t take up much room, and doesn’t require much maintenance, perhaps one of the several invertebrate species is for you.

This book provides biological information and care requirements for four commonly-kept varieties of invertebrates—centipedes, millipedes, scorpions and tropical cockroaches.  These animals require only the most simple of accommodations and the most minimal of care.  Once rare in captivity, they are now becoming more readily available, and the number of people keeping these unusual animals continues to grow rapidly.

Although these animals have many husbandry needs in common and there will thus be some overlap between sections, each section of this book is designed as an independent unit.  If you are keeping only one variety of these animals, you will find all the care information you need in that particular section.

Biology

All of the animal species covered in this book are arthropods.  In structure and behavior, they are very different from the more familiar vertebrate pets such as dogs, cats, hamsters or even snakes and turtles, and many of their life processes, such as respiration, circulation and reproduction, may be completely unfamiliar to most people.  It is helpful in caring for these animals, then, to have at least a basic knowledge of how an invertebrate body works.

The most obvious characteristic of an invertebrate, as the name implies, is that it lacks a backbone.  The more familiar petshop animals, such as dogs, cats, rodents, birds, reptiles and fish, are all vertebrates.  Their internal skeleton is based on the long vertebral column, made up of a string of round hollow bones, and all of the limb bones, ribs and skull attach themselves to this vertebral framework.  Invertebrates, however, not only lack a backbone, but they do not have any bones at all.  Instead of a hard internal skeleton supporting and surrounded by soft body tissues, the arthropods have a soft inner body surrounded and supported by a hard protective exoskeleton, and thus they reverse the engineering plan found in the vertebrates.

The external skeleton of an insect or other arthropod is a marvel of engineering.  It is lightweight but very strong, waterproof but still capable of allowing for the transfer of air and moisture in and out of the body.  The rigid framework allows the muscles to be extremely powerful—much stronger, proportionately, than those of larger animals.  If an adult human being were to have the same muscular strength, proportionately, as a typical-sized insect, he would be capable of lifting a loaded freight train with one hand, and then swinging it around his head.

The arthropods pay a heavy price for this superb protection, however.  The cells making up the outer cuticle layer are dead and cannot divide, and this means that the exoskeleton cannot grow.  As the arthropod grows and become larger, the exoskeleton becomes tighter and tighter, and it must be periodically shed and replaced by a new one if the animal is to grow.  This process is known as ecdysis or molting, and it is one of the most vulnerable points in any arthropod’s life.  During and immediately after the molting process, the arthropod is completely defenseless.  The new exoskeleton is soft and pliable, leaving the animal vulnerable to predators until the new skeleton has had time to dry and harden.  The molting process can also sometimes go awry, causing the animal to bleed to death or to be fatally trapped inside the old skeleton.  During its lifetime, a large arthropod may molt its exoskeleton as many as seven or eight times.

The body processes of arthropods are very different from those of the more common petshop animals.  Mammals and birds are said to be “warm-blooded”, which means that they can use internal body metabolism to maintain a constant high body temperature no matter what the outside temperature or environmental conditions might be.  Arthropods, on the other hand, like all of the invertebrates (and most of the vertebrates), are said to be “cold-blooded”.  The proper scientific designation for this is “ectothermy”, from the Latin words for “outside heat”, and this is a pretty good thumbnail description of the process.   Ectotherms do not produce their own body heat through metabolism, but instead use outside sources of heat, such as direct sunlight or radiant heat from rocks or sand, to maintain their proper internal body temperatures. 

Body temperature is an important factor for any living organism, since many biological processes depend on chemicals called “enzymes”, which work better at particular temperatures.  Heat can in a sense be thought of as an arthropod’s “fuel”—the warmer its body temperature is, the more rapid its biological processes can occur and the quicker it can move.  If cooled, however, its body processes slow down.  In areas that are too cold, ectotherms cannot maintain a body temperature high enough to carry on their biological processes, and they will die.  On the other hand, if the external temperature is too high, arthropods have no physiological method to reduce their body temperature to an acceptable level (they do not have sweat glands and cannot cool themselves by perspiring), and will also die.