Biology of Sole British Psoccptera, Wits Particular Referemce to Species Frequenting Foliage
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BIOLOGY OF SOLE BRITISH PSOCCPTERA, WITS PARTICULAR REFEREMCE TO SPECIES FREQUENTING FOLIAGE. By TIMOTHY RICHARD NEW, B.Sc., A.R.C.S. A Thesis presented for the Ph.D. Degree of the University of London. Imperial College Field Station, Silwood Park, Ascot, Berkshire. 305t 1968. -2- ABSICCT. Aspects of the bioloty of foliage-fregentinaPsocoptera were studied at Silwood. Park, Ascot, Berkshire from Autumn 1965 to Spring 1965.These insects were considered especially in relation to the total arboreal psocid fauna and to their main habitat. i.e. the foliage of different tree species. Psocid samples from litter and from trees were taken concurrently and were counted and identified. DescriTtions of the early stages and life histories of nine species are based on field and laboratory data. Several species were found only on some tree species and numbers of others showed large differences on different trees. Some of the factors that may influence the relative numbers of the same species of Psocoptera on different tree species were investigated. Counts of eggs on different tree species also revealed variations in psocid abundance. Aerial dispersal of Psocoptera was assessed with the aid of suction traps. The potential food supply of psocids on foliage of a range of tree species was compared at different times of the year and also with that consumed by psocids. The fecundity of several psocid species fed on foods from different trees was compared. Laboratory experiments showed that selection of oviposition site was related to characteristics of different leaf surfaces . The biology .of two groups of hymenopterous parasites of Psocoptera were examined, especially in relation to their fecundity and host specificity. A series of arthropods were identified as nredators of psocids and their numbers on different species of trees were compared. • A -3_ CONTENTS Page Introduction 6 Section I. Rearing Methods for Psocortera. 8 Introduction 8 Methods e The effect of temperature and humidity on development 12 Section 2. Early staes and life histories of British foliage- 17 frequenting Psocoptera. Introduction 17 Eggs 17 Nymphs 22 Life Histories 38 Overaintering in some Psocoptera 43 Section 3. Ps000ptera of Leaf Litter. 46 Introduction 46 Extraction Methods 47 Times of Extraction 49 Tyres of litter sampled 49 The Psocoptera obtained 50 Distribution in different types of litter 53 Temporal separation in litter 55 Habitat alternation and re-entry to the litter 55 Section 4. Psocontera on arboreal foliage. 58 Introduction 58 Samplinifs Methods 59 The numbers of psocids on different trees at different times of the year 63 The effect of tree size on psocid numbers 72 Distribution on single trees 73 Section 5. The Dispersal of Psocoptera. 76 Dispersal of nsocid eggs 76 Disnersal of nymhs of foliage-frequentin psocids 76 Dispersal of adults 78 Trapr:una Methods 80 110 -4- Page The numbers and species of Psocoptera trapped 81 Psocoptera in suction traps 81 Variation in catch with height of trap 85 Sex Ratio 86 Psocorte2a on sticky traps 36 Psocontara in water traps and light traps 87 Theaange of psocids that fly 87 The Reproductive State of flying psocids 88 Fli,ht Muscle Autolysis 89 Alary Polyorphism 91 Section 6. The Insect Parasites of Psoco)tera. 95 Introduction 95 Parasites of psocid eggs 95 Methods 97 Early Stages and Life History 97 The effect of host on the parasite I00 Parthenogenesis and Sex ilatio I0I Longevity, ovinosition and fecundity I0I Host finding and specificity 105 Parasites of psocid nymphs and adults 106 Methods 107 Amount of parasitism 108 Early stages and life Histories 109 Effect of parasite on the host 117 Section 7. The Arthropod Predators of Psocoptera 119 Introduction 119 on The numbers and kinds of arthromXnredatorsdilierent tree species Predators taken with psocid prey 121 Selection of prey in the laboratory 122 Section 8. Distribution and Mortality of eggs of foliage- frequenting Psocoptera. 124 Introduction 124 Methods 124 The numbers of egg batches on different trees 127 Mortality o overwintering eggs from different sites 129 Function of web covering egg batches 130 -5- Page Section 9. Ovinosition and fecundity of foliage-frequenting Psocoptera. 134 Introduction 134 The female reproductive system 134 The number of egg batches laid 138 The effect of food on fecundity 140 Selection of oviposition sites 14I Smoothness of surface 142 Chemical properties 143 Shape of leaves 145 Movement of leaves 145 Section 10. The leaf surface and psocid food. 148 Introduction 148 The potential food of psocids on leaf surfaces 148 Techniques for examination of leaf microflora and debris 149 The amounts, types and dispersion of adventitious matter on some leaf surfaces 150 The actual food of foliage frequenting psocids 156 Section II. Discussion. 162 Summary. 171 Acknowledgments. 175 References. 176 Appendix I. 186 Appendix 2. (Tables) 187 -6- INTROD.T.ETI011. Psocoptera are one of the more neglected orders of insects, and have attracted the attention of very few entomologists. Yost species have no economic importance and all are siAall and inconspicuous. Nearly 90 species have been recorded from Britain (Broadhead, 1964), and these may be divided into three broad ecological groups: I. Species associated with stored products, soil and ground litter, birds' nests and similar habitats. 2. Species found mainly on bark of many kinds of trees. 3. Species found mainly on arboreal foliage, rarely on bark. Pearman (1928a,b,c) in a series of classic papers laid the foundations of biological knowledge of the British. Psocoptera and since then Broadhead and Hobby (1944) have discussed the biology of a species of Liposcelis fltc,:Lenting stored products and Broadhead and Thornton (1955), Broadhead (1958) and Broadhead and Y:apshere (1966a,b) have given detailed accounts of the ecology of various species in the second of the above groups. No comprehensive accounts exist of the biology and ecology of species in the third category, i.e. the foliage-frequenting psocids. The present work is an attempt to provide such an account. Nine species are considered namely Trichowocus dalii (Mclachlan), Ectqpsocus briggsi Stenossocus immaculatus (Stephens), S.stigmaticus (Imhoff and Labram), Graphoosocus .3ruciatus (L.), Caecilius burmeisteri Brauer, C. flavidus (Stephens), C. fupoppterus (Latreille in Coquebert) and C. kolbei Tetens. The last seven belong to the Polypsocidae, and the other two to the PseudocaecilLidae. The familiar classification of these insects is in doubt, but the above groupings, and all nomenclature in this thesis follows that given in the most recent list of British specjies (Broadhead,I964) (see, howeyer,,Lee. and Thornton, 1967 t.Thornton and Wong 1967 ;Smithers,;I967'). The biology of Ectopsocus briggsis which is found. in a variet, of habitats, was discussed by 1eber (1931) and Sofner (1941), but only fragmentary accounts exist of some aspects of the bionomics of the more characteristic foliage-frequenting psocids which belong 1,- 1 the Polypsocidae ( Nelbe,IS604 Ludwig, 1908; Rule, 1916; Stagers 1917; Pearmans 1928asbsc; Modem, 1951; Broadhead and 71apsheresI960) It was hoped to describe the life histories of all arboreal foliage-fregenting psocids found in Britain, but one species (Enderleinella obsoleta (Stephens)) has not been found during the present study, and it has not been possible to obtain material from elsewhere. The other nine species were collected at Silwood Parks Berkshire, where most of the work described in the following pages was carried out. They all oviposit on foliage, and all stages live on and feed from loaf surfaces. The aim of this work was to investigate the biolagy of this group of psocithis to relate it to the total psocid fauna on trees, and also to the foliage that they frogent. In a study limited to two to three seasons it seemed more valuable to investigate bionomics on the broadest possible basis, and to lay a foundation for future more detailed work, rather tan to concentrate or. one aspect in detail. Descriptions of the life histories and of early stages are followed by data on the nunbers of psocids in leaf litterand on a number of tree species. Various factors influencing the numbers of foli .,-e-freqenting psocids on different trees are considered in later sections of this thesis. Literature relevant to each section is quoted in context. Tables of detailed data arc given in appendices, but figures are placed in context. SECTION 1. nearing Methods for Psocoptera Introduction. CoApacatively few authoEs ha,:e attempted to rear species of foliage-frequenting psocids, but there are several accounts of rearing stored-products psocids (see Broadhead and Fobby, 19443 Broadhead, 1961; Allen, 1960; Finlayson, 1949), and bark-frequenting psocids (aroadhead, 1947; 7]ertmoed, 1966; Jentsch, 19'59; Mockiord, 1957 Seiner, 1941; Sommerman, 1943 a, b, c, 1944). All methods used ace essentially similar, and provide for the ,aintenance of a high humidity and easy renewal of food supply. Thornton and Broadhead (1954) found that laboratory attempts to rear Elinsocus resulted in a very high mortality. There are no complete accounts of rearing arboreal Polypsocidae, although Medem (1951) .,fives S02.j fragmentary data. Peo=tn (in lit. 1967) did not succeed in rearing foliage-frequenting psocids, but he found that the other types were easier to breed. Several foliage species were maintained by Schneider (1955) in the laboratory, but he omits any account of rearing methods. During the present work, 31 species of psocids were reared in the laboratory through at least one a)mplete generation. Hortality and duration of development of sonic were compared under conditions of standard temperature and relative humidity. The species represented a wide range of ecological types, from those in stored products to the nine species of foliae frequenters here discussed. Aethods. Several kinds of rearing containers wee used with varying degrees of success. The most useful methods are of general application but others were designed foe special purposes, whioh are mentioned in • -9- context.