Laricobius

Rosenhauer, 1846

Laricobius is a Holarctic of small predatory in the , comprising approximately 23 described . Unlike other Derodontidae genera that feed on , Laricobius species are specialized of (Adelgidae), -like that infest conifers. Several species, notably L. nigrinus from western North America and L. osakensis from Japan, have been released as agents against the hemlock woolly adelgid (Adelges tsugae) in eastern North America. The genus exhibits two distinct morphological groups: a southeastern Asian/Himalayan group with shortened bodies and narrow lacking explanate margins, and a more widespread Holarctic group with elongate bodies and transverse, fully explanate pronota.

Laricobius erichsonii by (c) Sandy Rae, some rights reserved (CC BY). Used under a CC-BY license.

Laricobius nigrinus by (c) Evan M. Raskin, some rights reserved (CC BY), uploaded by Evan M. Raskin. Used under a CC-BY license.

Laricobius.erichsoni.-.lindsey by James K. Lindsey. Used under a CC BY-SA 3.0 license.

Pronunciation

How to pronounce Laricobius: //læˈrɪkoʊbius//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Identification to requires examination of shape (explanate vs. non-explanate margins), body proportions (elongate vs. shortened), and presence or absence of . A to species is available in the world review by Zilahi-Balogh (2011). Laricobius can be distinguished from other by their association with colonies and their of dropping from foliage to pupate in soil. are active from fall through early summer and may be found in association with woolly adelgid on hemlock twigs.

Images

Habitat

Associated with conifer forests, specifically where infest Tsuga (hemlock), Picea (spruce), and Abies (fir) . In North America, closely tied to eastern hemlock (Tsuga canadensis), western hemlock (T. heterophylla), and Carolina hemlock (T. caroliniana) forests. Species have been documented establishing in both forest and urban environments where trees occur.

Distribution

Holarctic distribution. Europe: 1 (L. erichsonii). North America: 3 species (L. nigrinus, L. rubidus, L. laticollis), with L. nigrinus native to the Pacific Northwest (Montana, Idaho, Washington, Oregon, British Columbia) and L. rubidus in eastern North America. Asia: 17 species, with centers of diversity in southeastern Asia and the Himalaya. L. nigrinus and L. osakensis have been to eastern North America for . L. erichsonii was introduced to eastern Canada and the Pacific Northwest for control of balsam woolly .

Seasonality

active from fall through early summer. Undergo summer (aestival ) coinciding with diapausing first sistens. occurs in spring. present in summer, feeding on adelgid and sistens . occurs in soil. Adult in fall. Synchrony between and is critical for effective .

Diet

Specialized of (Adelgidae). feed on adelgid . feed on adelgid eggs and sistens . Specific documented include Adelges tsugae (hemlock woolly adelgid), Adelges piceae (balsam woolly adelgid), and other adelgid .

Host Associations

Adelges tsugae - hemlock woolly ; primary target of releases
Adelges piceae - balsam woolly ; of L. erichsonii
Tsuga canadensis - eastern hemlock; tree of A. tsugae
Tsuga caroliniana - Carolina hemlock; tree of A. tsugae
Tsuga heterophylla - western hemlock; of L. nigrinus and A. tsugae in Pacific Northwest
Picea spp. - spruce; occasional for
Abies spp. - fir; occasional for

Life Cycle

(one per year). emerge in fall and are active through early summer. Adults undergo summer during hot months. laid in spring within woolly on twigs. hatch and feed on adelgid eggs and sistens . Mature larvae drop from foliage to soil to pupate. New adults emerge in fall. closely synchronized with adelgid .

Behavior

and are active . Larvae exhibit negative , dropping from foliage to soil for . Adults use visual and olfactory cues to locate -infested trees and specific stages. Adults can disperse between trees. Both feed within woolly adelgid . Adults have been observed to undergo () when prey are in .

Ecological Role

of , serving as a natural agent. In ranges, contributes to regulation of adelgid on hemlock and other conifers. In ranges (eastern North America), being evaluated and deployed for of eastern hemlock forests threatened by hemlock woolly adelgid. can reduce adelgid and improve tree health metrics such as new shoot production.

Human Relevance

Important agents for management of forest pests. L. nigrinus released in eastern North America since 2003; over 400,000 individuals released from Georgia to Maine. L. osakensis released since 2012. L. erichsonii to eastern Canada (1933 onward) and Pacific Northwest (1957-1960) for balsam woolly control. methods include beat sheets, specialized collection containers (Lari-Leuco container), and environmental . Establishment success varies geographically, limited by winter temperatures in northern areas. Regulatory concerns arose regarding inadvertent introduction of L. naganoensis with L. osakensis shipments.

Similar Taxa

Other Derodontidae genera (Derodontus, Peltastica, Nothoderodontus)Other in feed on rather than ; Laricobius distinguished by predatory habit and association with adelgid colonies
Leucopis (silver flies)Also used as agents for hemlock woolly ; distinguished by being () rather than , with pupating on twigs rather than dropping to soil

More Details

Phylogenetic Groups

recognizes two major groups: (1) southeastern Asian/Himalayan with shortened bodies and narrow lacking explanate margins, and (2) widespread Holarctic species with elongate bodies and transverse, fully explanate pronota. The latter includes four Asian species without collected from Tsuga infested with Adelges tsugae.

Biocontrol Regulatory Issues

L. naganoensis was inadvertently imported to eastern North America with L. osakensis. USDA subsequently permitted its introduction as a without standard public review or Environmental Assessment, raising concerns about circumvention of regulatory safeguards for agents.

Detection Challenges

Larval stages of L. nigrinus and L. osakensis are difficult to distinguish morphologically. Environmental methods have been developed to detect and differentiate these in soil, water, and matter to improve .