AN ABSTRACT OF THE THESIS OF Bruce Dudley Cowan for the M. S. in Entomology (Name) (Degree) (Major) Date thesis is presented April 12, 1965 Title THE BIOLOGIES OF PREDATORS (COLEOPTERA: CLERIDAE) OF THE DOUGLAS -FIR BEETLE, DENDROCTONUS PSEUDOTSUGAE HOPKINS ( COLEOPTERA: SCOLYTIDAE), IN WESTERN OREGON Abstract approved (Major Professor) Six species of Cleridae, including Enoclerus spegeus Fabricius, E. lecontei Wolcott, E. schaefferi (Barr), E. eximius Mannerheim, Thanasimus undatulus Say, and an undescribed species of Enoclerus, were found on Douglas -fir in western Oregon. E. sphegeus was the only clerid of the six species studied which was primarily associated with the Douglas -fir beetle, as the other clerids occurred more often with Scolytus unispinosus or other small scolytids. E. sphegeus and T. undatulus each had a life span of two years, the first year of which was spent in the immature stages. E. sphegeus and T. undatulus adults emerged during the latter part of the summer, apparently overwintered in bark crevices, and appeared on Douglas - fir beetle- infested trees the following spring. Both species survived as adults approximately a year in the field, and E. sphegeus lived up to nearly a year and a half in the laboratory. E. lecontei adults emerged throughout the summer, survived no more than two months in the laboratory, and gave no indication of overwintering in the adult stage. Clerids mated frequently throughout their adult life. Mating ap- peared to be stimulated by a pheromone produced by the females. Two larval instars were found in E. sphegeus, three in T. unda- tulus, E. lecontei, and Enoclerus sp. , and four in E. schaefferi, al- though none of the E. schaefferi larvae pupated. E. sphegeus larvae fed on all stages of Douglas -fir beetle brood during the first instar, and fed mostly on Douglas -fir beetles from the third instar to callow adult in the early part of the second instar. After the first few weeks, most second instar larvae did not feed, but left the Douglas -fir beetle galleries and remained relatively inactive throughout the winter and spring in pupal cells, constructed in the outer bark of infested trees or in chunks of partly decayed bark on the ground, until the following July or August when they pupated. A few prepupal larvae in the outer bark were parasitized by a species of Ichneumonidae. E. sphegeus adults apparently did not consume their potential of Douglas -fir beetles in the field due to lack of available Douglas -fir beetle adults throughout most of the year. E. sphegeus larvae were rather ineffective as predators, since they occurred mainly where Douglas -fir beetle gallery density was high, and merely reduced competition of Douglas -fir beetle brood rather than causing a decrease in the population. THE BIOLOGIES OF PREDATORS (COLEOPTERA :CLERIDAE) OF THE DOUGLAS -FIR BEETLE, DENDROCTONUS PSEUDOTSUGAE HOPKINS (COLEOPTERA: SCOLYTIDAE), IN WESTERN OREGON by BRUCE DUDLEY COWAN A A THESIS submitted to OREGON STATE UNIVERSITY in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE June 1965 APPROVED: Assistant Professor of Entomology In Charge of Major Chairman of Department of Entomology Dean of Graduate School Date thesis is presented April 12, 1965 Typed by Marion F. Palmateer ACKNOWLEDGMENTS The writer would like to express his deep appreciation to the following people for their help in the preparation of this thesis: To Dr. William P. Nagel who helped outline the project, care- fully reviewed the thesis, and offered many helpful suggestions. To Dr. Julius A. Rudinsky under whom the project originated. To Dr. Kenneth E. Rowe for his suggestions concerning statisti- cal analysis of sampling data. To Orlo Jantz, Gary Daterman, Willard Harwood, Gordon Howse, John McGhehey, and Richard Johnsey who helped in the col- lection of data. To my wife, Judy, for her encouragement, understanding, and helpful comments regarding the writing of this thesis. TABLE OF CONTENTS Page INTRODUCTION 1 LITERATURE REVIEW 3 The Douglas -fir Beetle . 3 Enoclerus sphegeus Fabricius . .. 5 Seasonal History 8 Host Attraction . 10 Feeding 10 Larval Mortality 13 Sex Determination 13 Enoclerus lecontei Wolcott . 14 Thanasimus undatulus Say 15 Enoclerus schaefferi (Barr) 17 Enoclerus eximius Mannerheim . 18 Other Predators 18 Principles of Predation 20 METHODS 23 Studies of Adult Cleridae 23 Emergence 24 Overwintering 25 Feeding 25 Mating and Oviposition . 26 Clerid Density Observations 27 Lincoln Index 28 Studies of Larval Development . 29 Instar Determination and Growth Rates . 30 Larval Migration 32 Bark Samples 32 Statistical Computations 33 Page RESULTS AND DISCUSSION 37 Studies of Adult Cleridae 40 Sex Determination 40 Emergence 40 Adult Seasonal History 43 Mating and Oviposition 52 Studies of Larval Development 57 Seasonal History and Development 65 Larval Feeding 76 Studies of Predator Effectiveness 77 SUMMARY 90 BIBLIOGRAPHY 93 LIST OF FIGURES Figure Page 1 Enoclerus sphegeus approaching a Douglas -fir beetle . 12 2 Emergence of adult Cleridae in 1963, from logs in- fested with Douglas -fir beetles and Scolytus unispino- sus 44 3 Adult life span of three species of Cleridae in the field 47 4 Seasonal occurrence of E. sphegeus adults and Douglas - fir beetle adults, observed in five -minute periods on the bark surface of two trees, compared with accumu- lated Douglas -fir beetle attacks 49 5 Enoclerus sphegeus copulating 55 6 Seasonal history of immature development of E. sphegeus collected during 1963 and 1964 70 7 Seasonal history of immature development of E. lecontei collected during 1963 and 1964 71 8 Seasonal history of immature development of E. sphegeus and Douglas -fir beetle during the summer of 1964 74 9 Average densities of E. sphegeus larvae under bark during the summer of 1964 75 10 Line of regression for E. sphegeus larval densities, related to inches of Douglas -fir beetle parent gallery per square foot, from July 1 to September 5, 1964 . 87 LIST OF TABLES Table Page 1 Emergence of different species of Cleridae from logs containing Douglas -fir beetle broods and ma- terial containing Scolytus unispinosus broods in 1963 39 2 Douglas -fir beetle adults killed or eaten per preda- tor per day at 75°F. by adult Cleridae continually supplied with living prey for 30 days 39 3 Adult insects eaten, attacked, or ignored by adult E. sphegeus in the field and /or laboratory 45 4 Densities of E. sphegeus adults, observed on the bark surface of two windthrown trees, related to Douglas -fir beetle attack densities, from May 10 to June 30, 1964 51 5 Average number of eggs laid by E. sphegeus in the laboratory at 75°F. throughout each month of active adult life span 53 6 Maximum number of eggs laid by one female preda- tor in the laboratory at 75°F 53 7 Head capsule widths of the larval instars of Cleridae in millimeters 59 8 Development of five species of Cleridae at 70° F . 60 9 Development of E. sphegeus at different temperatures 61 10 Development of E. lecontei at different temperatures 62 11 Development of T. undatulus at different temperatures 63 12 Development of Cleridae from egg to adult at different temperatures, from Tables 8, 9, 10, and 11 . 64 Table Page 13 Square -foot bark samples containing different densi- ties of E. sphegeus larvae from July to September, in 1963 and 1964 78 14 Douglas -fir beetle brood survival related to different densities of E. sphegeus larvae during the summer of 1964 83 15 Difference of Douglas -fir beetle brood survival in samples containing 3 -7 E. sphegeus larvae and samples containing no E. sphegeus (Table 14). 84 16 E. sphegeus larval densities related to inches of Douglas -fir beetle parent gallery per square foot of bark, from July 1 to September 5, 1964 85 17 Survival of Douglas -fir beetle brood from August 1 to August 15, 1964, in 12 samples with three to seven E. sphegeus larvae and 12 samples with no E. sphegeus, where samples were paired according to Douglas -fir beetle parent gallery length and density . 89 LIST OF PLATES Plate Page 1 Adult Cleridae: A, Enoclerus sphegeus; B, Eno- clerus lecontei; C, Enoclerus sp. ; D, Thanasimus undatulus 7 2 Ventral view of the abdomen of E. sphegeus, showing external sex differences: A, male; B, female . 42 3 Immature development of Enoclerus sphegeus: A, eggs; B, first instar larva newly hatched; C, first instar larva in pre -molt form; D, second instar larva as orange, feeding form; E, mature, lilac - colored second instar larva; F, pupa 67 4 Enoclerus sphegeus adult attacking a Douglas -fir beetle 81 THE BIOLOGIES OF PREDATORS (COLEOPTERA :CLERIDAE) OF THE DOUGLAS -FIR BEETLE, DENDROCTONUS PSEUDOTSUGAE HOPKINS (COLEOPTERA: SCOLYTIDAE), IN WESTERN OREGON INTRODUCTION The Douglas -fir beetle, Dendroctonus pseudotsugae Hopkins (Coleoptera: Scolytidae), is one of the most destructive insects of Douglas -fir, Pseudotsuga menziesii (Mirb. ) Franco, throughout its range. In western Oregon the Douglas -fir beetle normally infests only windthrown timber, and is usually able to attack standing trees only following a year of excessive blowdown. The Douglas -fir beetles, which build up tremendous populations in the excessive blowdown, are then forced to make mass attacks on standing trees. Heavy attacks on a tree reduce its resistance until it is completely overcome by Douglas- - fir beetles. The tree is killed by the girdling action of the Douglas - fir beetles in the cambium and by the introduction and spread of blue - stain fungus, Ceratocystis spp. , which is carried and introduced by the beetles. Many board -feet of timber may be killed before the Douglas -fir beetle population subsides. Although the origin of a Douglas -fir beetle epidemic in western Oregon depends primarily on the amount of available windthrown ma- terial, the decline of Douglas -fir beetle populations is caused by the combination of weather, host resistance, competition, predation, and z parasitism.