Phloeosinus punctatus

LeConte, 1876

western cedar bark beetle

Phloeosinus punctatus is a in the , Scolytinae, known as the western cedar bark beetle. The colonizes giant sequoia (Sequoiadendron giganteum) and California incense-cedar (Calocedrus decurrens) in the Sierra Nevada mountains of California. Females initiate gallery construction and mate monogamously. The undergoes four larval , typically producing one per year under natural conditions. It has been observed to contribute to branch mortality in giant sequoia, particularly when trees are under environmental stress.

Pronunciation

How to pronounce Phloeosinus punctatus: /flɛoʊˈsaɪnəs pʌŋkˈteɪtəs/

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Identification

A small (exact size not documented in sources). Entrance holes in bark are beveled oblong in shape, created by tunneling at an angle; exit holes are circular, formed by progeny exiting perpendicular to the bark surface. emerging from giant sequoia diverge morphologically from those emerging from incense-cedar, though specific diagnostic characters for field identification are not detailed in available sources.

Habitat

Giant sequoia (Sequoiadendron giganteum) groves in the Sierra Nevada mountains of California, at elevations of 1,710–2,060 meters. Colonizes weakened or dying branches high in the and branches that fall to the forest floor. Also occurs in stands of California incense-cedar (Calocedrus decurrens). represent a mesic segregate of xeric pine-oak forest of mid- and upper-montane Sierra Nevada.

Distribution

to California, restricted to approximately 70 giant sequoia groves encompassing ~11,000 hectares scattered across the western slope of the Sierra Nevada mountains. Documented from Calaveras State Park, Sequoia- Canyon National Park (multiple groves including Giant Forest, General Grant, Redwood Mountain), and Yosemite National Park (Mariposa and Merced groves). GBIF records indicate presence in British Columbia, Canada and Alaska, USA, though these may represent misidentifications or require verification.

Seasonality

activity from late spring through early fall. data from 2021 showed alighting on fallen branches from May 20 to August 20, with peak landing on July 2. Predicted of F1 offspring from branches between July 10 and September 1, with peak emergence on August 8. Branch-fall from giant sequoia crowns occurs primarily during winter and early spring months, creating breeding substrate for subsequent .

Diet

Inner bark and partially sapwood of trees in the Cupressaceae. Feeding and occur in inner bark and partially in sapwood.

Host Associations

Sequoiadendron giganteum - primary giant sequoia; show strong preference and reproductive success
Calocedrus decurrens - California incense-cedar; emerge from this but do not reproduce in it
Thuja plicata - western redcedar; reported in literature as primary agent of mortality, though not directly studied

Life Cycle

Progresses through four larval . Typically one per year under natural conditions; two generations per year observed under laboratory conditions. emerge from branches. Reproductive output averages 28 per kilogram of giant sequoia branch material.

Behavior

Females initiate gallery construction. Mating is monogamous. from giant sequoia show strong preference for giant sequoia and do not reproduce in incense-cedar, despite being capable of emerging from the latter. tunnel at an angle to create entrance holes; progeny exit perpendicular to bark surface creating circular exit holes.

Ecological Role

Potential contributing factor in giant sequoia mortality, particularly when trees are under environmental stress such as drought or wildfire. Significant branch loss from (averaging ~30 branches per tree, with 20%–50% of trees per site shedding branches) may affect and hydraulic function, especially under drought conditions. May amplify damage to trees already under environmental stress. No fatal attacks on giant sequoia directly attributed to this reported in earlier literature, though high abundances have emerged from crowns of mature trees that subsequently died.

Human Relevance

Of management concern in giant sequoia groves due to potential role in tree mortality under stress conditions. Branch-fall creates fuel loads and safety hazards. Ecological and management implications discussed in forestry and contexts.

Similar Taxa

Phloeosinus species on incense-cedar and morphologically divergent, but phylogenetic analysis shows no clear sequence divergence; distinguished by association and subtle morphological differences
Other Phloeosinus species contains multiple on Cupressaceae; specific identification requires detailed examination and association data