SUBSCRIPTIONS In 2019 Phil. Trans. R. Soc. B (ISSN 0962-8436) will be published Continuing its long history of infl uential scientifi c publishing, Phil. Trans. R. Soc. B 26 times a year. For more details of publishes high quality theme issues on topics of current importance and general subscriptions and single issue sales interest within the life sciences, guest-edited by leading authorities and comprising please contact our fulfi lment agent: new research, reviews and opinions from prominent researchers. Each issue Turpin Distribution aims to create an original and authoritative synthesis, often bridging traditional The Royal Society Customer Services Pegasus Drive disciplines, which showcases current developments and provides a foundation for Stratton Business Park future research, applications and policy decisions. Biggleswade SG18 8TQ United Kingdom royalsocietypublishing.org/journal/rstb T +44 1767 604951 F +44 1767 601640 E [email protected] EDITOR Karen Liu Alternatively, please contact our customer John Pickett Satyajit Mayor service team at: Ewa Paluch E [email protected] SENIOR COMMISSIONING EDITOR Jean-Paul Vincent Helen Eaton Roland Wedlich-Söldner PRICES FOR 2019 PRODUCTION EDITOR Neuroscience and cognition Online Online Simon Clackson Anna Borghi only and print Nicole Creanza EDITORIAL BOARD Andreas Engel £ UK/rest of World £2649 £3708 Organismal, environmental Barry Everitt and evolutionary biology Kristine Krug € Europe €3444 €4821 Tim Benton William Marslen-Wilson $ US/Canada $5014 $7019 Dora Biro Julie Morand-Ferron Patrick Butler Richard Morris Roger Butlin Michael Petrides SUBMISSIONS Sonia Harmand Jenny Read For submission guidelines and access to Barbara Helm Anil Seth journal content visit: Nick Lane Joan Silk royalsocietypublishing.org/journal/rstb Cate Macinnis-Ng Mriganka Sur Nathalie Pettorelli Gary Westbrook Philosophical Transactions of the Royal Naomi Pierce Min Zhuo Society B: Biological Sciences Rebecca Sear ISSN: 0962-8436 Health and disease Zehao Shen © The Royal Society, 2019 Chetan Chitnis Stephen Simpson Except as otherwise permitted under the Rodrigo Correa-Oliveira John Speakman Copyright, Designs and Patents Act, 1988, Sebsebe Demissew Xiangjiang Zhan this publication may only be reproduced, Christl Donnelly stored or transmitted, in any form or by any Cellular and developmental biology Charles ff rench-Constant other means, with the prior permission in Lionel Christiaen Keith Gull writing of the publisher, or in the case of Stephen Cohen Sunetra Gupta reprographic reproduction, in accordance Richard Dixon Michael Hochberg with the terms of a licence issued by the Julian Dow Peter Hudson Copyright Licensing Agency. In particular, Patricia Pestana Garcez Gagandeep Kang the Society permits the making of a single Andreas Hejnol Joanne Lello photocopy of an article from this issue Jonathan Hodgkin Katrina Lythgoe (under Sections 29 and 38 of this Act) for an Penny Jeggo C. Jessica Metcalf individual for the purposes of research or Karen Lipkow Cliona O’Farrelly private study. Open access articles, which are published under a CC-BY licence, may be re-used without permission, but subject to acknowledgement. Cover image Plant virus-carrying small brown planthoppers feeding on rice. Credit: Jinting Yu. Typeset by Nova Techset Private Limited, Bengaluru & Chennai, India. Printed in the UK by Latimer Trend. This paper meets the requirements of ISO 9706:1994(E) and ANSI/NISO Z39.48-1992 (Permanence of Paper) eff ective with volume 335, issue 1273, 1992. Phil. Trans. R. Soc. B (ISSN 0962-8436) is published 26 times a year for US$6461 per year by the Royal Society, and is distributed in the USA by Agent named Air Business, C/O Worldnet Shipping USA Inc., 149-35 177th Street, Jamaica, New York, NY11434, USA. US Postmaster: Send address changes to Phil. Trans. R. Soc. B, C/O Air Business Ltd, C/O Worldnet Shipping USA Inc, 149-35 177th Street Jamaica, New York, NY11414. RRSTB_374_1767_Cover.inddSTB_374_1767_Cover.indd 55-7-7 004/01/194/01/19 66:49:49 PPMM.