Durham E-Theses The feeding ecology of certain larvae in the genus tipula (Tipulidae, Diptera), with special reference to their utilisation of Bryophytes Todd, Catherine Mary How to cite: Todd, Catherine Mary (1993) The feeding ecology of certain larvae in the genus tipula (Tipulidae, Diptera), with special reference to their utilisation of Bryophytes, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/5699/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk 2 THE FEEDING ECOLOGY OF CERTAIN LARVAE IN THE GENUS TIPULA (TIPULIDAE, DIPTERA), WITH SPECIAL REFERENCE TO THEIR UTILISATION OF BRYOPHYTES Catherine Mary Todd B.Sc. (London), M.Sc. (Durham) The copyright of this thesis rests with the author. No quotation from it should be published without his prior written consent and information derived from it should be acknowledged. A thesis presented in candidature for the degree of Doctor of Philosophy in the University of Durham, 1993 FEB t99^ Abstract Bryophytes are rarely used as a food source by any animal species, but the genus Tipula (Diptera, Tipulidae) contains some of the few insect species able to feed, and complete their life-cycle, on bryophytes. Vegetation particle volumes ingested by larvae of eleven Tipula species increased only marginally between instars and not to the extent expected from the rate of growth of body mass. Early and late instars within a species frequently ingested similar sized particles. The overall efficiency of digestion of vegetation particles was low and similar between the four instars of each of the eleven species. Generally, the only method by which later larval instars can obtain a higher proportion of nutrients is by feeding on a larger number of smaller vegetation particles and not by ingesting large particles. In feeding choice experiments, Tipula confusa preferred moss species from woodland habitats, whereas Tipula subnodicornis did not show an overall preference for either woodland or moorland moss species. Tipula subnodicornis also showed a less extensive hierachical preference/avoidance than Tipula confusa for the ten moss species investigated. The moss species Campylopus paradoxus and Sphagnum papillosum accumulated Pb'^'*' ions and Zn^"^ ions to high concentrations. There was some evidence that Tipula subnodicornis larvae were deterred from feeding on these mosses with high levels of introduced heavy metal ions. Tipula montana was able to thrive and complete its life-cycle in Britain at lower altitudes than had been previously thought. Individuals of this species show a combination of one-year and two-year life-cycles at Waskerley Common. The feeding methods employed by Tipula species can explain why some of them have remained as consumers of br>'ophytes. I certify that all material in this thesis which is not my own work has been identified and that no material is included for which a degree has previously been conferred on me The copyright of this thesis rests with the author. No quotation from it should be published without her prior written consent and information derived from it should be acknowledged For mv mother and father Acknowledgements I should like to express my sincere gratitude to my supervisor, Dr. John Coulson, for all his help, advice and constructive criticism throughout this study. I would like to thank Profs. Ken Bowler and Peter Evans for providing facilities in the Department of Biological Sciences, University of Diu'ham. I should also like to thank Dr. Bill Block and Roger Worland of the British Antarctic Survey; particularly for facHitatiag the use of the Atomic Absorption Spectrometer. I am grateful to the following people for their help and support in a variety of ways: Eric Henderson, particularly for assistance in fieldwork and technical support, Dr. Tusi Butterfield, Carol Fielding, Michael Bone, Robin Ward, Norman Cobley, Pablo Corcuero, Trina Clarke and Lina Powell. Also, I should like to thank Perdy for her 'assistance' in the field! I should also like to thank English Nature for allowing me access to the Moorhouse National Nature Reserve; Mr. Lampton, for allowing me to work on Waskerley Common, and his gamekeepers, particularly Dennis Dodds, for their advice and assistance in carrying out fieldwork there; and Raby Estates for allowing me access to Chapel Fell. A very big thank you goes to Murray Grant for all his support and encouragement during the last four years. Finally, a very special thank you goes to my parents for their support, both financial and moral, throughout the course of this study. A fourth instar larva of Tipula montana, Contents Page 1, GENERAL INTRODUCTION 1 2. AN INVESTIGATION INTO THE SIZE OF VEGETATION 6 PARTICLES INGESTED IN LARVAE OF THE GENUS TIPDLA 2.1. Introduction 6 2.2. Methods 9 2.2.1. Larvae in the genus ripula 9 2.2.1.1. Methods by which vegetation 9 particles were obtained 2.2.1.2. Determination of vegetation particles 10 ingested 2.2.2. Detailed study on Tipuia rufina 10 2.2.3. Additional studies on Hydriomena 10 furcata and Locusta migratoria 2.3. Results 11 2.3.1. Comparison of size of vegetation 11 particles ingested through the instars in species of Tipula 2.3.1.1. Instar I 14 2.3.1.2. Instar II 14 2.3.1.3. Instar III 14 2.3.1.4. Instar IV 15 2.3.2. Mandible length in Tipula species 15 2.3.2.1. Comparison of mandible 15 length between the species 2.3.2.2. Relationship between mandible length 18 and the vegetation particle volume ingested 2.3.2.3. Relationship between mandible length 18 and the weight of a larva 2.3.3. Spiracular disc diameters in ripula 21 species 2.3.3.1. Comparison of spiracular disc diameter 21 through the species 2.3.3.2. Relationship between the vegetation 21 particle volume ingested and spiracular disc diameter 2.3.4. Determination of the variability of 28 vegetation particles ingested 2.3.5. Comparison of the increase in the 31 biometric measurements and vegetation particle volumes ingested in Tipula species 2.3.5.1 In moss-feeders 31 2.3.5.2. In non-moss feeders 34 2.3.6. Results of the detailed study on 35 Tipula rufina 2.3.7. Results on the studies on Hydriomena 35 furcata and Locusta migratoria 2.4. Discussion 41 3. THE EFFICIENCY OF DIGESTION OF VEGETATION 45 PARTICLES BY LARVAE FROM THE GENUS TIPULA 3.1. Introduction 45 3.2. Methods 46 3.3. Results 47 3.3.1. Total damage per particle caused 47 by larvae 3.3.1.1. Comparison with the spiracular disc 47 diameters 3.3.1.2. Comparison with the vegetation particle 47 volumes 3.3.2. Determination of the proportion of 51 damaged cells in the vegetation particles 3.3.2.1. Total damage to vegetation particles 51 occurring between the instars 3.3.2.2. Damage in the edge cell region of the 55 vegetation particles 3.3.2.3. Damage in the mid-cell region of the 64 vegetation particles 3.3.2.4. Comparison of damage in the edge and 64 mid-cell regions 3.3.3. Determination of consumers of dead plant 65 material 3.4. Discussion 67 FOOD CHOICE EXPERIMENTS ON TIPULA SUBNODICORNIS 70 AND TIPULA CONFUSA 4.1. Introduction 70 4.2. Description and habitats of the moss 72 species used in the experiments 4.2.1. Moorland mosses 72 4.2.2. Woodland mosses 73 4.3. Methods for studying food preferences 74 4.3.1. Method for using the choice experiments 75 4.3.1.1. Larval availability and collection 75 4.3.1.2. Justification of the experimental methods 75 4.3.1.3. Experimental details 76 4.3.1.4. Method for the calculation of the results 77 4.3.1.5. Food choice experiment between Eriophorum 77 vaginatum, Campylopus paradoxus and Sphagnum papillosum 4.3.2. Method for the analysis of the frass, to 78 compare with the spot observation method 4.3.2.1. Experiments using choices of single or 7 9 mixed food plants 4.3.3. Methods for the three preliminary 79 experiments 4.3.3.1. Compaction experiment 7 9 4.3.3.2. Effect of illumination and darkness 80 on food choices 4.3.3.3. Mobility of the larvae in multiple 80 choice petri-dishes 4.4 Results 81 4.4.1. Results of the preliminary experiments 81 4.4.1.1. Compaction experiment 81 4.4.1.2. Effect of illumination and darkness 81 on food choices 4.4.1.3. Mobility of the larvae in multiple 81 choice petri-dishes 4.4.2. Results of the food choice experiments 85 4.4.2.1. Food choice experiments between 93 Eriophorum vaginatum, Campylopus paradoxus and Sphagnum papillosum 4.4.3. Analysis of moss particles in frass and 93 the comparison between the spot observation and frass analysis methods 4.4.4.