The Bark and Ambrosia Beetles of California (Coleoptera: Scolytidae and Platypodidae)

175 Pages·2003·16.77 MB·English

BULLETIN OF THE CALIFORNIA INSECT SURVEY
VOLUME 16
THE BARK AND AMBROSIA BEETLES
OF CALIFORNIA
Coleoptera: Scolytidae and Platypodidae
BY
D. E, BRIGHT, JR. and R. W. STARK
UNIVERSITY OF CALIFORNIA PRESS
THE BARK AND AMBROSIA BEETLES OF CALIFORNIA
(Coleoptera: Scolytidae and Platypodidae)
BULLETIN OF THE CALIFORNIA INSECT SURVEY
VOLUME 16
THE BARK AND AMBROSIA BEETLES
OF CALIFORNIA
Coleoptera: Scolytidae and Platypodidae
BY
D. E. BRIGHT, JR. and R. W. STARK
UNIVERSITY OF CALIFORNIA PRESS
BERKELEY LOS ANGELES LONDON
1973
BULLETIN OF THE CALIFORNIA INSECT SURVEY
Advisory Editors:
J. N. Belkin, R. M. Bohart, Paul De Bach, R. L. Doutt, W. H. Lange, E. I. Schbger, D. D. Jensen
VOLUME 16
Approved for publication September 22, 1972
Issued September 10, 1973
UNIVERSITY OF CALIFORNIA PRESS
BERKELEY AND LOS ANGELES
UNIVERSITY OF CALIFORNIA PRESS, LTD.
LONDON, ENGLAND
ISBN 0520-09480-8
LIBRARY OF CONGRESS CATALOG CARD NUMBER: 72819676
@ 1973 BY THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
PRINTED BY OFFSET IN THE UNITED STATES OF AMERICA
CONTENTS
.........................................................
Introduction 1
Ecological and Economic Importance ................................ 1
.........................................................
Bionomics 3
Distribution ....................................................... 4
.......................................................
Morphology 6
..........................................................
Methods 7
Acknowledgments .................................................. 8
..............................................
Systematics and Biologies. 9
Key to the Families Platypodidae and Scolytidae., ...................... 9
................................................
FamilyPlatypodidae
..................................................
Genus Platypus 9
..................................................
Family Soolytidae 10
...................................................
Key to Genera 11
.............................................
Subfamily Scolytinae 14
.................................................
Tribe Swlytini 14
..............................................
Genus Scolytus 14
Subfamily Hylesininae ............................................ 21
................................................
Tribe Hylastini 21
...........................................
Genus HyIastinus 21
...............................................
Genus scierus 21
Genus Hylwgops ............................................2 2
..............................................
Genus Hylastes 25
................................................
Tribe Hylurgini 28
Genus Dendroctonur .......................................... 28
...............................................
Tribe Hylesenini 34
...........................................
Genus Xylechinus 34
.......................................
Genus Pseudohylesinus 35
............................................
Genus Leperisinus 41
Genus Alniphugus ........................................... 41
..........................................
Genus Phloeosinzrs 43
...........................................
Genus Chramesus 52
..............................................
Tribe Hypoborini 53
........................................
Genus Chuetophbeus 53
Tribe Polygraphini .............................................. 56
Genus Carphoborus ......................................... 55
V
vi contents
.................................................
Tribe Micracini 60
Genus Cactopinus ............................................6 0
...........................................
Genus Stenoclyptes 62
Genus Pseudothysanoes ....................................... 63
Genus Thysanoes ............................................. 64
............................................
Genus Hylocu~us 64
.............................................
Genus Micracis 65
Tribe Cryphalini .............................................. 66
Genus Cryphalus ........................................... 66
Genus Procryphalus ........................................... 67
.........................................
Genus Taenwglyptes 67
Genus Hypothenemus .........................................6 8
Tribe Crypturgini ............................................... 70
Genus Cryptwgus ............................................ 70
.............................................
Genus Dolurgus 70
rib xyloterini ................................................ 71
Genus Typodendron ......................................... 71
Tribe Dryocoetini ............................................... 73
........................................
Genus Dendrocranulus 73
............................................
Genus Dryocoetes 74
...........................................
Genus Coccoty pes 75
................................................
Tribe Xyleborini 76
.............................................
Genus Xylebms 76
.....................................................
Tribe Ipini 78
Genus Pityogenes ........................................... 78
Genus Pltyoktdws ..........................................8.0
..........................................
Genus Orthotomicus 82
..................................................
Genus Ips 82
................................................
Tribe Corthylini 94
Genus Monurthrum ......................................... 94
............................................
Tribe Pityophthorini 96
..........................................
Genus Dendroterus 96
Genus Myebborus .......................................... 96
Genus Conophthonrs ........................................ 97
..................................
Genus Pseudopityophthorus 101
Genus Pityophthotw .......................................... 103
Genus Ancyloderes ...........................................1 16
..........................................
Genus Gnuthotricus 117
........................
List of Host Plants and Scolytids Attacking Them 119
.......................................................
Literature Cited 123
..........................................................
Plate-Figures 131
...................
Index to the Scolytidae and Platypodidae of California 165
vi
THE BARK AND AMBROSIA BEETLES
OF CALIFORNIA
Coleoptera: Scolytidae and Platypodidae
BY
D. E. BRIGHT, JR. and R. W. STARK
INTRODUCTION
THIS BULLETIN attempts to bring together in one source, of North Carolina and Minnesota have been treated by
keys, descriptive comments, distributional notes, host Beal and Massey (1945) and Dodge (1938) respectively
data, and biology of every species of Scolytidae and and most of the important genera have been revised
Platypodidae found within the state of California. More or reviewed (Blackman 1928b, 1931a, b, 1934, 1938,
than 170 species in 44 genera are treated. 1940,194l,1942ayb ; Bright 1963,1967,1968,1969;H op-
s.
Scolytidae, commonly known as "bark and ambrosia ping 1963b, cy 19&Q,1965abYyc , d, e; L. Wood 1954a,
beetles,".are small, cylindrical insects which feed and 1961, 1963). Most of these publications have included
reproduce in the tissues of living, dying, or recently Californian species and all but Hopping have described
dead trees and shrubs. They constitute the most serious new species from California. Miscellaneous new species
threat to the forest industry in the United States and from Califonha have been described by S. L. Wood
Canada. In view of their secluded habitat, these insects (1964) and Bright (1964,1966,1967, and 1971). Wood
are infrequently collected by general collectors and (in Hatch, 1971c) has discussed the species occurring
subsequently are poorly known in much of the world. in the Pacific Northwest and also mentions those species
It is hoped that the information presented in this bul- that occur in California.
letin will aid in the study of this fascinating and impor-
tant group of insects in California and adjacent regions. ECOLOGICAL AND ECONOMIC IMPORTANCE
The terminology utilized here is essentially the same
as that used by Swaine (1918) and Wood (1951 to The scolytid fauna of California is unusually rich in
date). genera and species for an area the size of California in
The first comprehensive review of the bark beetles of a predominantly temperate climate. The diversity of
North America was published in 1876 by LeConte and genera and species is due to the great physical and
Horn. At that time, 127 species were recognized. In climatic variation and the large number of real and
1918, Swaine discussed the species occurring in Canada. potential hosts which occur in the state. Munz and Keck
Chamberlin ( 1939) brought together all the scattered (1959) recognize 11 vegetation types with 29 distinct
species descriptions, revisions, and other taxonomic plant communities, 26 of which contain woody shrubs,
literature published up to that date. His work contains trees, or host records of scolytids. A conservative esti-
about 550 species and is still the only complete treat- mate of potential hosts exceeds 400 species.
ment of North American bark beetles. It is considered No other state has such extreme ranges of physical
to be the starting point for recent research. conditions. Elevations range from 90 meters below sea
There has been considerable interest in the scolytids level in Death Valley to about 4,800 meters above sea
because of their economic importance. The bark beetles level at Mt. Whitney only a few miles away. Two great
1
2 Bulletin of the California Znsect Suroey
series of mountain ranges, the Coast Ranges and the cannot be absorbed into the economy and these are real
Sierra Nevada extend almost the entire length of the resource losses. The southern pine beetle, in the south-
state. The southern end of the Cascade Range extends eastern United States, and the mountain pine, western
into northern California. pine, Douglas-fir, and Engelmann spruce beetles in the
The climate is affected by most western air mass western states are capable of great local and regional
systems, e.g., polar maritime, tropical maritime, polar destruction.
continental, and continental. Frost-free days range from Such outbreaks may occur naturally in mature and
365 near the coast to fewer than 100 at elevations above overmature forests initiated by such predisposing events
2,000 meters. Rainfall ranges from less than 5 cm in as fire, windthrow, and flooding, but most are, directly
Death Valley to more than 275 cm in Del Norte County. or indirectly, man-caused. Poor logging and manage-
Scolytids are found in almost all such environments- ment practices, urbanization, air, water, and soil pollu-
wherever woody plants can survive. tion, and other abuses all predispose trees and forests
to bark beetle outbreaks.
ECOLOGICAILM PORTANCE Logging, without appropriate attention to prevention
of spread of root diseases, has resulted in an increase
The scolytid fauna is of particular importance in the in intensity and distribution of root pathogens. The
evolution of forest stands. In an undisturbed forest debilitating effect of root pathogens on shrubs and
succession they commonly feed upon and kill the excess trees has apparently made them more susceptible (or
plants in the stand. It is only when such stands reach a less resistant) to attack by bark beetles. Given an in-
climax stage and become decadent from a predomi- crease in a suitable habitat or food source the beetle
nance of overmature trees that natural “outbreaks” populations increase in numbers until they exceed the
occur. This results in a release of the understory and a predisposed supply and attack “healthy” plants in the
new phase of succession begins. outbreak phase.
Many scolytids also aid in the recycling process
necessary for maintenance of forest soils and plant suc- MANAGEMENOTF SCOLYTIPDO PULATIONS
cession. They do this by their physical activities of tun-
nelling and reducing a significant portion of the fiber The concept of pest management is slowly replacing
to a more readily decomposable form; by changing the the “insect control” philosophy. Bark beetle control in
state of the wood so that other insects can further re- the past, and to a large degree today, has relied upon
duce it; by introducing pathogens which further en- removal of infested trees and destruction of the infested
hance the decomposition process; and by accelerating portion or felling infested trees and destroying them or
the effect of physical factors such as temperature and spraying with an insecticide such as lindane or benzene
moisture. hexachloride (BHC). That such treatments kill bark
Bark and ambrosia beetles are an important link in beetles has been well established and probably has a
food chains. They play host to a vast array of entomo- temporary local effect in reducing pest numbers. How-
phagous insects, mites, and nematodes and are an im- ever, the value of such endeavors over large forested
portant source of food for many vertebrates, principally areas and for long-term population regulation is ques-
birds and small mammals. They are an integral part of tionable.
faunal ecosystems and contribute to the stability of Under the concept of pest management, two princi-
plant communities as much as or more than they con- pal means of regulating a bark beetle population will
tribute to instability. emerge-prevention and the use of an integrated control
system. Prevention, well known but largely ignored,
ECONOMIICM PORTANCE basically consists of avoiding those practices which
weaken trees or plants and practicing good forest man-
Much has been written about the destruction of agement so that stands are vigorous and healthy. Con-
forest resources by bark and ambrosia beetles. Annual sideration is given to such matters as the optimum
“loss” figures are published citing billions of board feet number of plants that can be grown on a given site to
of timber destroyed with “values” usually in the mil- minimize competition for nutrients and space, selection
lions of dollars. The majority of such estimates are of the tree best suited to a particular site, harvesting
inflated, for most trees of commercial size, if salvaged at an age when the tree is still vigorous-prior to decline
promptly, lose little market value. in vigor due to overmaturity-and other forestry prac-
However, bark beetle outbreaks do destroy vast sup- tices. In noncommercial or unmanaged areas such as
plies of timber which cannot be salvaged, or which primitive or wilderness areas, such treatments should
Bright and Stark: The Bark and Ambrosia Beetles of California 3
not be used and should usually not pose a severe threat angle, directly into the cambium region. In the case of
to surrounding well-managed stands. ambrosia beetles, the adult bores directly into the wood
Where treatment is necessary, an integrated control for a distance of several centimeters. The first evidence
system offers the greatest potential for reducing popula- of attack is the appearance of reddish or whitish boring
tions. An integrated control system utilizes all means of dust or pitch tubes under or around each entrance hole.
population suppression that are compatible and which Both monogamy and polygamy are characteristic
will cause the least disruption to the ecosystem. For conditions, depending on the genus involved. In all
example, a system might consist of heavy cutting in an known cases of polygamy, the male initiates the en-
area known to be a chronic center of beetles, stump and trance hole and is subsequently joined by three to five
soil treatment to prevent invasion by root pathogens, females. In the case of monogamous species, the female
trapping of flying beetle populations using chemical makes the initial attack and is joined by the male. Mat-
attractants, encouragement of woodpecker populations ing may take pIace in the gallery, on the surface of the
by leaving a suitable number of nesting trees or using host plant, or before the insects leave the host plant of
artificial nesting boxes, and introduction of mass-reared the parents.
parasites or predators, or both. Simultaneously the nu- Females of true bark beetles tunnel away from the
trient value and water capacity of the soil would be entrance hole in the cambium region and lay eggs
determined and depending on the findings, fertilization, singly or in groups abng the gallery. The eggs may be
soil amelioration, draining, or irrigation may be con- laid in specially constructed niches along the gallery
sidered. wall or scattered in the boring dust along the gallery.
The use of these methods demands a thorough knowl- Females of the ambrosia beetles lay eggs scattered
edge of the bionomics of the particular species of along the gallery or in niches.
scolytid involved. The larvae of true bark beetles generally mine at
right angles to the parent gallery and may or may not
BIONOMICS engrave the sapwood. The larval mines may continue in
a straight line or curve in various directions. Later
The biology and ecology of relatively few species of instars usually mine with the grain of the wood.
Scolytidae have been studied in any great detail. The Adult galleries may be packed with frass and boring
genera Dendroctonus, Scolytus, Ips, Phloeosi.nus, and dust (e.g., Dendroctonus) or kept clean, the frass being
Pseudohyksinus have been the subjects of detailed pushed out the entrance hole (e.g., Ips). Larval mines
studies, primarily because of their economic importance. are always packed with frass. Some species mine en-
Data on the bionomics of species in the remaining tirely in the inner bark and the larval mines are exposed
genera are usually confined to a knowledge of the when the bark is removed. Others may mine for a short
gallery pattern or the host or both. period in the inner bark, then complete their feeding
All members of the family, with a few exceptions, in the outer bark, while other species feed entirely in
feed and reproduce in the cambium region (true bark the outer bark. The larval mines may be straight and
beetles) or deep in the wood (ambrosia beetles) of very regular or they may be vexy irregular and meander-
dying, injured, or fallen trees and shrubs. The majority ing. However, they rarely cross one another unless the
of Californian species attack forest trees, of which the beetles are crowded. In those species which lay their
conifers are preferred hosts. Other hosts such as nuts eggs en masse in grooves or cavities, the larvae fre-
and cones serve as breeding places for the few excep- quently extend their brings as a group, forming an
tions. enlarged chamber without distinct IarvaI mines; or the
All woody parts of a tree are attacked, but beetles mines may be contiguous at first, becoming separated in
of each genus generally restrict their activities to a later instars. The larvae of ambrosia beetles feed in
particular portion. For example, Pi&pphth and larval *cradles” constructed by the parent beetle.
Myeloborus are found in smaller branches and twigs; Pupation occurs in enlarged cells at the end of the
Conophthorus in the cones; Ips in the larger branches, larval mines in the inner bark, in the cambium region,
bole, and tops; Dendroctonus is found only in the bole in the outer bark or, in the case of ambrosia beetles, in
and sometimes in the roots and HyZurgops and HyIastes the cradles or in the open mines. Most emerging beetles
are most often found in the lower portions and roots. exit individually, boring their own exit hole which often
Species in all these genera may be found in a single results in characteristic patterns on the bark. New
pine tree. adults of ambrosia beetles generally exit through the
After selecting a suitable location, usually under a parental entrance galleries.
bark scale, under moss or lichens, or in a bark crevice, The number of generations per year varies consider-
the beetle bores a hole, generally at a slight upward ably depending on the species involved and the climatic
4 Bulletin of the California Insect Suruey
“
factors of its habitat. One to two generations per year I . ” Y T T 7 9 Y 7 ‘P r . 1
seem to be most common with more in the lower ele-
vations and the south and fewer in the higher eleva-
tions and in the narth.
A characteristic and most interesting part of scolytid
biology is the adult egg gallery under the bark (figs.
1-28). In uncrowded conditionst hese galleries are often
very symmetrical and interesting in appearance. The
galleries may be so characteristic in the family that
one familiar with gallery patterns can readily identify
the genus, or in some cases the species, responsible for
the work.
Several analyses of the gallery patterns are available
(Bml and Massey, 1945; chamberlin, 1939, 1958;
Swaine, 1918; Traghardh, 1930). All these authors use
essentially the same terminology in discussing the vari-
ous types of galle.ries.
Three types of ambrosia beetle galleries are found in . .-.
the California forests. These are: cave type (Xylebm), I p
u
simple tunnel (Pbtyps, fig. l), and the compound IC * --.A
_ _ I , . # . Y D U I ”
tunnel (Trypodendron, fig. 20, Gnathotrichus, figs. 1,
28, and Monarthrum, fig. 27). All these tunnels are Map 1. Boreal (dark stippled) and austral (light stippled)
regions showing the biotic subdivisions occupied by
excavated in the wood. The cave type is merely an en- bark beetles shown in table 1.
larged chamber; the simple tunnel goes directly into
the wood and has no side tunnels and the compound the relative wealth of species, it may be noted that Japan
type is a branched tunnel which contains individual and India, both areas rich in Scolytidae, each have
cells or cradles in which the larvae develop. barely 200 specie ( Browne, 1961).A bout 30 percent of
Eight types of galleries can be recognized as the work the total number of species for North America are repre-
of the true bark beetles. These are: cave type (Den- sented in California. This high percentage reflects the
droctonus ualens); radiate or star-shaped type (Ips, diverse ecology and topography of the state.
figs. 22,23, Pityophthorus, fig. 26, Carphobm, Dyo- The desert area of the southern part of the state with
coetes, Orthotomicus and others); forked type (Scolytus its disjunct mountain ranges and high degree of floral
uentralis, fig. 3, Alniphugus aspericollis, fig. 10, various endemism is of special interest. This area produces most
species of Pseudohylesinus, figs. 7, 8. and others); of the endemic genera and species of Scolytidae found
simple longitudinal or transverse (Phloeosinus, figs. 11- in the state. The northern portion of the state and the
15, Scolytus unispinosus, fig. 4, Dendroctonus p d e - forested regions of the Sierra Nevada contain genera
rosae, fig. 6, and others); irregular elongate tunnels with a boreal distribution, and most of these are also
(Dendroctonus breuicomis,f ig. 5);p ith tunnels (Myelo- Holarctic. This is the same fauna, with few exceptions,
borus and some Pityophthorus, fig. 26); wood tunnels that occurs in the Pacific Northwest.
(Micra& and Hylomrus); and cone tunnels (Conoph- In order to discuss adequately the distribution of
thorus). No attempt will be made to describe each type species within California, the biotic areas presented by
in detail since they have been adequately treated by Miller (1951) and utilized by Hurd and Michener
the authors mentioned above. (1955) have been adopted. The terminology utilized
here is essentially the same as that used by Hurd and
DISTRIBUTION Michener. They recognize two broad faunal areas in
the state-boreal and austral. The boreal region includes
Among the 44 genera discussed in this paper, more all the forested portions of the coast, the Sierra Nevada,
than 170 species occur within the state. This is an un- and the isolated mountain ranges of southern Califor-
usually high number of species for an area the size of nia. The boreal region is further divided into the North
California in the temperate region. As an indication of Coast, Sierran Montane, Southern California Montane,