INSECT PHYSIOLOGY Insect Physiology

V. B. WIGGLESWORTH C.B.E., M.D., F.R.S.

Emeritus Professor of Biology, University of Cambridge. Formerly Director, Agricultural Research Council Unit of Insect Physiology

SEVENTH EDITION

ISBN 978-0-412-11150-1 ISBN 978-1-4899-3202-0 (eBook) DOI 10.1007/978-1-4899-3202-0 This title is available in both hardbound and paperback editions. The paperback edition is sold subject to the condition that it shall not, by way of trade or otherwise, be lent, re-sold, hired out, or otherwise circulated without the publisher'S prior consent in any form of binding or cover other than that in which it is published and without a similar condition including this condition being imposed on the subsequent purchaser. All rights reserved. No part of this book may be reprinted, or reproduced or utilized in any form or by any electronic, mechanical or other means, now known or hereafter invented, including photocopying and recording, or in any information storage and retrieval system, without permission in writing from the Publisher. Distributed in the U.S.A. by Halsted Press, a Division ofJohn Wiley and Sons Inc., New York Library of Congress Catalog Card Number 74-1548 Contents

page Introduction vii

1. The Integument 1 Cuticle structure. Composition of the cuticle. The epicuticle. Surface forces and the insect cuticle. The moulting, formation and pigmentation of the cuticle. The mechanism of moulting and of hatching. Metallic colours of the cuticle.

2. Respiration 15 The tracheae and tracheoles. The diffusion theory of insect respiration. Function of the spiracles. Ventilation of the tracheal system. The regulation of respiration. Regulation of tracheal supply. Respiration of aquatic insects. Respiration of parasites.

3. The Circulatory System and Associated Tissues 33 Mechanism of the circulation. Control of the heartbeat. Composition of the blood. Cytology of the blood. Functions of the blood. Organs and tissues associated with the blood.

4. Digestion 46 The alimentary canal. Proventriculus. Peritrophic membrane. Salivary glands. Secretion. Reaction of the gut. Digestive enzymes. Symbionts in digestion. Absorption. The faeces.

5. Excretion 62 Excretion of dyes. 'Nephrocytes'. Urate cells and storage excretion. Pigments as excretory products. Verson's glands. Malpighian tubules and the urine. Excretion in Rhodnius. Excretion in other insects. Excretion in aquatic insects. Regulation of osmotic pressure and ionic composition of the v vi CONTENTS haemolymph. Accessory functions of the Mal• pighian tubules. 6. Nutrition and Metabolism 78 Food requirements. Vitamin requirements. Micro• organisms and symbionts as sources of vitamins. Water metabolism. Cold resistance. Temperature of insects. Respiratory metabolism. Anaerobic metabolism. Metabolism and chemical changes during growth and metamorphosis. Some chemical products of insects. Pigment metabolism. Light production. 7. Growth 96 Growth ratios. Moulting. Metamorphosis. Chemistry of insect growth hormones. Histolysis and histogenesis. Regeneration. Determination of sex. Determination of other characters. Pattern and gradients. Arrested growth or diapause. 8. Reproduction 114 Male and female reproductive organs. Oogenesis and oviposition. Mating, impregnation and ferti• lization. Factors controlling fertility and fecundity. Hibernation and diapause. Special modes of reproduction. 9. Muscles and Movement 126 The physiological properties of insect muscles. Locomotion. Flight. 10. The Nervous System, Sense Organs and 133 Behaviour The nerve cord and ganglia. The brain and suboesophageal ganglion. Reflex responses in the normal insect. Orientation. Sense organs: mechanical senses. Proprioception. Hearing. Chemical senses. Temperature and humidity senses. Vision. Colour vision. Insect behaviour. 11. The Endocrine System 154 Nervous system and hormones. Neurohaemal organs. Endocrine glands. Pheromones. Indo: 159 To the insect, order and disorder are exposed to sight and so we think to see the little emmets confer and locking their antennae immediatly transmit the instinctiv calls which each and all can feel: whereas the mutual fellowship of distributed cells hath so confronted thought that explanation isfetch'd from chemic agency: because in that science the reaction of unknown forces is described and summ'd in mathematic formulae pregnant of truth, and of such universal scope that, being call'd laws, their mere description passeth for Efficient Cause. -ROBERT BRIDGES Introduction

The fundamental processes of vital activity, the ordered series of physical and chemical changes which liberate energy and maintain the 'immanent movement' of life, are probably the same wherever 'living matter' exists. The description of these changes is the ultimate goal of physiology, of whatever group of organisms; but in this book we shall be concerned only with physiology on a humbler plane: with the grosser functions of the organs and tissues, and with the mechanisms by which these functions are co-ordinated to serve the purpose of the insect as a whole. Of all the zoological classes, the insects are the most numerous in species and the most varied in structure; the general physiology of the group is therefore only too apt to be obscured by the endless specializations of particular forms; and the main difficulty of a work like the present is the exclusion of all that is special and non• essential, and the retention of only that material which best illustrates the general theme. There are, indeed, certain common factors which condition the physiological make-up of the insects, and these factors serve, to some extent, to link them all together into one system. They are essentially terrestrial animals. This circum• stance determines the characters of their cuticle, and this, in turn, conditions their respiratory mechanism and the physiology of their growth. The respiratory mechanism and the cuticular skeleton are vii viii INSECT PHYSIOLOGY among the factors which restrict the size of insects. Their small size and terrestrial habit render them very prone to lose water; and the urgent need for the conservation of water influences the respiratory, excretory and digestive systems. All these systems show special changes when the insect reverts to an aquatic life. Yet, although the interaction of these factors results in some uniformity ofprinciple in the physiology ofinsects, their diversity in habit, food and environment causes such endless variation in detail, that, quite apart from the conspicuous gaps in our present know• ledge, any limited treatment of the subject must in any case be more or less arbitrary in presentation; and, were there space to insert them, nearly all the generalizations that are attempted should have qualifying instances. The history of insect physiology is peculiar. The early micro• scopists, Hooke, Malpighi, Leuwenhoek, made many observations on the structure ofinsects, and many accurate inferences about their physiology. More was added by the great naturalists, Swammerdam, Reaumur, de Geer. But, with such conspicuous exceptions as Newport, Graber, Lubbock, Plateau, and others of more modem times, the majority ofentomologists, until recent years, have been so fully occupied with the morphology and taxonomy of their colossal group that such advances in physiology as have been made have commonly been mere by-products of morphological study. From time to time we find the physiologists ofthe last century, Dutrochet, Treviranus, Marshall Hall, von Kolliker, Claude Bernard, turning to the insects to illuminate their theme; but their concern was not with the insect as such. Within recent years, interest in the physiology ofinsects has arisen in a new quarter. The applied entomologist, confronted with the ravages of insects in the spheres of agriculture and of public health, has wanted to know something about their nutrition, about the laws governing their responses to sensory stimuli, about their reactions to parasites, about the precise way in which their bodies are adapted to diverse climatic conditions, and about the action upon them of toxic sprays and gases. With this demand for increased knowledge has come a realization of our present ignorance. Since the first edition of this book was published almost forty INTRODUCTION ix years ago extensive advances have been made in all parts of the subject. Full-sized textbooks have been devoted to it; notably The Principles of Insect Physiology by the present author, the three volume Physiology of the Insecta edited by Morris Rockstein, and Insect Biochemistry by Darcy Gilmour; and articles describing the most recent advances in the physiology and biochemistry of insects appear in the Annual Review of Entomology, in Advances in Insect Physiology and elsewhere. References in this edition have therefore been confined to such textbooks and reviews, to a few recent papers which have not yet become incorporated in this way, and to a limited number of other papers which provide useful starting-points for further reading.