Ladybirds

Published by Pelagic Publishing

www.pelagicpublishing.com

PO Box 725, Exeter, EX1 9QU

Ladybirds (2nd Edition)

Naturalists’ Handbooks 10

Series editors

S. A. Corbet and R. H. L. Disney

ISBN 978-1-907807-07-7 (paperback)

ISBN 978-1-907807-37-4 (eBook)

Text © Pelagic Publishing 2013

Key illustrations © Sophie Allington 1989

Other illustrations © Sophie Allington 1989 and © Chris Shields 2012

All rights reserved. Apart from short excerpts for use in research or for reviews, no part of this document may be printed or reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, now known or hereafter invented or otherwise without prior permission from the publisher.

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library.

Contents

Editors’ preface

Acknowledgements

1 Introduction

2 Life history

3 Ladybirds in their environment

4 Ladybirds and their natural enemies

5 Variation in ladybirds

6 Population and evolutionary biology

7 Ladybird distribution

8 Identification of British ladybirds

I: Field key to adult British ladybirds

II: Key to all the adult British Coccinellidae

III: Field key to the larvae of British ladybirds

9 Study techniques and materials

References

Index

Editors’ preface

The first edition of this book appeared in 1989, and since then there have been great changes in the world of ladybirds. Our friend and colleague Mike Majerus, who died suddenly in 2009, was the senior author of the first edition, and did much to stimulate interest in the group through his books, through the Cambridge Ladybird Survey and in his teaching. The enthusiasm that he inspired lives on, and we are delighted that such a strong team of his co-workers has agreed to produce this second edition. New discoveries and changes in the British ladybird fauna have made this a major undertaking. When the first edition was prepared male killers had not been recognised, the bryony and harlequin ladybirds were not yet established in Britain, and some important topics had hardly been explored. This book incorporates the newly-arrived species into the keys, and includes much other new material, notably on the evolutionary relationships of ladybirds, the role of chemical cues in searching behaviour, the distributional response to environmental change, and the impact of the recently-introduced harlequin ladybird. We are also fortunate to have splendid new illustrations by Chris Shields to supplement the excellent artwork that Sophie Allington prepared for the first edition.

Thanks to the work of numerous research workers and amateur recorders throughout the country, the subject of ladybird natural history has made important advances since the book first appeared. This substantially revised edition will make the new developments accessible to a wider audience, and perhaps encourage readers to undertake further research on these engaging insects.

SAC

RHLD

Acknowledgements

First and foremost we would like to express our deepest thanks to Mike Majerus and Peter Kearns. The first edition of this book has been an inspiration to so many people and it has been a privilege and a pleasure to build on their tremendous work. Many others have played a part in the production of this book and we are grateful to them all. We would like to thank Dr Sally Corbet for her diligent editing and encouragement throughout. We have also been extremely pleased to have supportive comments from Dr Henry Disney. Both Sally and Henry have inspired us throughout our careers and we have enjoyed the opportunity of working with them on this book.

There are many entomologists who have contributed to our understanding of ladybirds in Britain and we are grateful to them all. We would particularly like to thank the people involved in promoting biological recording of ladybirds in Britain over the years, both the volunteers who have led the Coccinellidae Recording Scheme in its various guises and staff from the Biological Records Centre (within the NERC Centre for Ecology & Hydrology). We are extremely grateful to Andrew Duff, Mark Telfer, Darren Mann and Amoret Spooner for kindly providing comments on the revised keys. Charlotte Coombes scanned the original text and her help was greatly appreciated.

We thank our families (David, Katy and Ella Roy, Clare Walker, Cameron and Jodie Brown, John, Sue, David and Jenny Comont, Guy Poland, Ilja Zeilstra) for their patience and interest in our passion for these amazing beetles.

Finally, we must thank all the people who have enthusiastically sent us their observations and records of ladybirds. One recorder Robert (Bob) Frost is worthy of special mention. His contribution to ladybird recording is represented by both the outstanding number of ladybird observations that he provided to the UK Ladybird Survey and also the happy memories that we have of working with him. He will be greatly missed.

Helen Roy, Peter Brown, Richard Comont, Remy Poland and John Sloggett

Reader feedback

We welcome feedback from readers – please email us at [email protected] and tell us what you thought about this book.

About Pelagic Publishing

We publish scientific books to the highest editorial standards in all life science disciplines, with a particular focus on ecology, conservation and environment.

Pelagic Publishing produces books that set new benchmarks, share advances in research methods and encourage and inform wildlife investigation for all.

If you are interested in publishing with Pelagic please contact [email protected] with a synopsis of your book, a brief history of your previous written work and a statement describing the impact you would like your book to have on readers.

1 Introduction

Biological science must stand on its foundations in basic observations of organisms in the field: what they do, when they do it, why they do it, and how they have come to do it.

Majerus, 1994

1.1 Introduction

Ladybirds are among the most attractive and popular of British insects. Many species are common. They may be found in almost any habitat from sea coast to mountain top, and from city wastelands to windswept heathlands. Almost every garden will have at least one species and many will have five or more species.

There are a number of reasons for the popularity of ladybirds. Firstly, ladybirds are charismatic insects. Many ladybirds have bright contrasting colour patterns, although not all are red with black spots. Some are black with red spots, others are yellow and black, or brown with cream spots. Some have stripes instead of spots and some no spots at all. Secondly, most species of ladybird are carnivorous. Both adults and larvae feed on aphids or other pest insects, which suck sap and damage many crops and garden plants. So, ladybirds are important predators of these pests and are considered ‘beneficial insects’. Finally, ladybirds are connected with good fortune in many myths and legends. The name ‘ladybird’ is itself derived from the commonest species in Britain, the 7-spot ladybird, Coccinella septempunctata. The lady in question is Our Lady, the Virgin Mary. The red colour is said to represent her cloak, which in early paintings and sculptures was usually depicted as being red, and the seven black spots represent the seven joys and seven sorrows of Mary.

Yet, despite their popularity and important function as predators of pest insects, much is still unknown about the behaviour and ecology of British ladybirds.

This book aims to outline what is known about the species found in Britain, and to highlight areas worthy of scientific exploration. We hope that the book will encourage you to discover more for yourselves, particularly through your own natural history studies and scientific research. Ladybirds offer great scope for original observations and experiments, and their potential as biological control agents of plant pests makes new contributions to our knowledge of ladybirds even more worthwhile. Additionally although a few species of ladybird are increasing in number, there are some historically widespread and common species that are currently declining dramatically (Roy and others, 2011; Roy and others, 2012)* and so increased understanding of their ecology and response to our rapidly changing environment is critical.

1.2 What are ladybirds?

Ladybirds are beetles and so belong to the largest order of organisms, the Coleoptera. There are two important characteristics that, taken together, distinguish ladybirds and most beetles from insects of other orders.

(i) The forewings are modified to form hard or leathery elytra (wing cases) that meet in the centre line, covering the abdomen.

(ii) The mouthparts are adapted for biting rather than sucking. Beetles generally and ladybirds in particular are unlikely to be confused with any other order except the Hemiptera (true bugs). The characters that distinguish ladybirds from bugs are shown in fig. 1.

Ladybirds are one family of beetles called the Coccinellidae. Coccinellids are small or medium-sized beetles, 1–10mm long; they are usually round or oval. The most obvious features of the upperside of a resting ladybird are the elytra, which in many species are brightly coloured and usually patterned with spots, bands or stripes. The elytra cover and protect the membranous flight wings (fig. 2) which are usually folded under the elytra when the ladybird is not flying. Between the elytra and the head is the pronotum. This is a plate which covers the upper surface of the thorax. It is broader than it is long and it extends forwards at the margins (fig. 3). The pronotum is often patterned, though not as brightly as the elytra. The head is retractable under the pronotum and the antennae are short and slightly clubbed. The legs are short and retract into grooves under the body. The feet (tarsi) have four segments, but because the third segment is small and hidden inside the deeply lobed second segment, only three segments are readily visible (fig. 4).

More than 4,500 species of coccinellid have been described worldwide. Forty-seven species are resident (established and reproducing) in Britain, and 27 of these also reside in Ireland. Various other species have been recorded on a few occasions in Britain, but they are not generally considered resident here (see chapter 7). Some of the British coccinellids (sub-family Coccidulinae) are small and unspotted, and would not normally be recognised as ladybirds. Whilst all 47 coccinellid species are listed in Table 1 and included in the key, this book primarily covers the 26 species that have received most research attention and were designated as conspicuous species in the first edition of this book.

Fig. 1. The differences between ladybirds and true bugs (Hemiptera).

Ladybirds

(a) The wing cases (elytra) meet on the centre line and do not overlap, and are hard.

(b) Head with biting mouthparts and with palps.

True bugs

(c) The forewings overlap, and are partly or completely membranous.

(d) Head with mouthparts modified into a pointed structure for piercing and sucking. The rostrum usually points backwards. Lacks palps.

Fig. 2. The membranous hind wing of a 7-spot ladybird.

Fig. 3. The position of the pronotum between the head and elytra (eyed ladybird, Anatis ocellata). head

Fig. 4. The lower part of a leg of a ladybird showing the tibia, the four tarsal segments (note the small third segment almost hidden within the second segment) and the tarsal claw.

Table 1. Classification of coccinellids occurring in Britain and Ireland (According to Duff , 2008; Roy and others, 2011, but also refer to Plate 1 for proposed revised phylogeny)

Family: Coccinellidae

* indicates the species is found in Ireland, as well as in Britain

# thought to be extinct in Britain

Henosepilachna (= Epilachna); Hippodamia variegata (= Adonia variegata); Tytthaspis (= Micraspis); Myzia (= Neomysia); Psyllobora (= Thea); Coccinella magnifica (= C. distincta). A comprehensive checklist of Coleoptera (including synonyms) was published by Duffin 2008. The checklist can be accessed through the Coleoptera website (www.coleoptera.org.uk) hosted by the Biological Records Centre.

Scientific names: In the entomological literature the numbers in the scientific names may be given in full (for example Subcoccinella vigintiquattuorpunctata), or may be simplified (for example Subcoccinella 24-punctata). Throughout this book we will refer to the ladybirds using the English name (where appropriate) but table 1 can be used as a cross-reference to the Latin name.

* References cited under the authors’ names in the text appear in full in the reference list.

2 Life history

2.1 General life cycle

Like all beetles, ladybirds pass through three stages - egg, larva and pupa - before reaching the adult state. So, like butterflies and moths (Lepidoptera), bees, wasps and ants (Hymenoptera) and true flies (Diptera), they are said to be holometabolous insects (undergoing complete metamorphosis).

Fig. 5. General life cycle scheme of a ladybird (based on the 7-spot ladybird).

For many ladybird species in Britain the full life cycle takes a year. Eggs are laid in spring or early summer. The larvae feed up over the next month or so, and the new generation of adults emerge from the pupae in mid to late summer. These adults feed but do not usually breed until the following spring, and so most species have just one generation a year (fig. 5). However, there are exceptions to this pattern. The rate at which larvae develop is affected by both temperature and food availability, and the development of eggs and pupae is also affected by the temperature. In some years, a number of species such as the 2-spot and 14-spot ladybirds have a second generation. Harlequin ladybirds in Britain generally have two generations, and sometimes a partial third generation, each year. For species completing more than one generation a year, individuals from both the early and late generations overwinter together. There are records of the 2-spot, 14-spot, cream-spot and eyed ladybirds surviving through a second winter. However, more information is needed if we are to be sure how common these exceptions to the normal pattern are, particularly in response to climate change.

Fig. 6. 7-spot ladybird laying a batch of eggs.

2.2 Eggs

The eggs of most ladybird species are elongate and oval, and vary from a light yellow to a deep orange colour. They are laid on the leaves, stems and sometimes the bark of plants, often in the vicinity of prey. Most species fix their eggs at one end so they are found in an upright position (fig. 6), though the eggs of the pine ladybird are frequently laid on their sides. There is considerable variation in the number of eggs laid at one time, though most species lay batches of eggs, which are tightly packed together forming a cluster on the substrate. Females of the 2-spot ladybird typically lay between 20 and 50 eggs at a time. There is also substantial variation within a species in the number of eggs laid per female (fecundity). One of the more important influences is the type of food eaten by the adults. Hariri (1966) found that the 2-spot ladybird laid a lifetime total of 738 eggs per female, averaging 9.3 per day when fed on the black bean aphid (Aphis fabae), but when the pea aphid (Acyrthosiphon pisum) was used, the total was 1535 eggs, laid at an average of 20.4 per day. Fecundity is also affected by the quantity of food eaten, so, for example, there is a positive correlation between food consumption and egg production in the 11-spot ladybird (Ibrahim, 1955a, b). Influences on larval development also affect subsequent female fecundity. Sundby