Megabruchidius dorsalis

(Fåhraeus, 1839)

honey locust seed beetle, Asian seed beetle

Megabruchidius dorsalis is an seed beetle (Chrysomelidae: Bruchinae) native to Asia that has established across Europe and North America. The is oligophagous on Caesalpinioideae seeds, primarily developing within pods of Gleditsia species. exhibit freeze-avoidant cold strategy with supercooling points around -10°C. The has demonstrated range expansion in its introduced range, colonizing North American Gymnocladus dioica in addition to its native Asian Gleditsia hosts.

Megabruchidius dorsalis by (c) agujaceratops, some rights reserved (CC BY), uploaded by agujaceratops. Used under a CC-BY license.

Megabruchidius dorsalis by (c) carnifex, some rights reserved (CC BY), uploaded by carnifex. Used under a CC-BY license.

2017 08 22 Megabruchidius dorsalis by Slimguy. Used under a CC BY 4.0 license.

Pronunciation

How to pronounce Megabruchidius dorsalis: /ˌme.ɡə.bruːˈkɪd.i.əs dɔːrˈseɪ.lɪs/

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

Identification

emerge from seed pods through characteristic exit holes. Identification relies on examination of antennal patterns and association with Gleditsia or Gymnocladus plants. Molecular identification may be required for definitive confirmation given similarity to other bruchine beetles.

Images

Habitat

Urban and suburban environments associated with ornamental Gleditsia triacanthos (honey locust) plantings. Found in areas where mature seed pods accumulate on ground or remain on trees. Established in parks, streetscapes, and managed landscapes across introduced range.

Distribution

Native to Asia (Oriental region). Introduced and established in Europe (first recorded Italy 1989; subsequently Slovenia, Croatia, Belgium, Ukraine, Eastern Black Sea region, and at least 15 European countries). North American records include association with introduced Gymnocladus dioica. GBIF records confirm presence in Belgium.

Seasonality

active during warmer months; from seed pods occurs when mature pods are available. strategy involves cold with supercooling point depression through cryoprotectant accumulation.

Diet

Obligate seed developing entirely within seeds of Caesalpinioideae (Fabaceae). Larvae consume endosperm and embryo tissues within seed coat.

Host Associations

Gleditsia triacanthos - primary honey locust; most common in introduced European range
Gleditsia fera - native recorded from Taiwan in native range
Gymnocladus dioica - expanded Kentucky coffeetree; North American native colonized in introduced range

Life Cycle

Complete with development entirely within seed pods. deposited on or within pods. Larvae mine into seeds and feed internally, creating characteristic exit holes upon as . Multiple per year possible in favorable climates. adults demonstrate freeze-avoidant physiology with cryoprotectant accumulation (glycerol, lipid) and cryoprotective dehydration.

Behavior

use antennal and mouthpart to locate plants. Females deposit on lower leaf surfaces or within pods; egg-covering with excrement has been observed in related bruchine as anti- defense. Adults capable of long-term survival under cold stress through maintenance of supercooled state.

Ecological Role

Seed reducing reproductive output of plants. demonstrate enemy release hypothesis counterexample: Gymnocladus dioica experiences seed in introduced range where M. dorsalis is present, but lacks seed predators in its native North American range. Potential competitive interactions with native seed predators in invaded regions unknown.

Human Relevance

Pest of ornamental Gleditsia triacanthos in urban landscaping. Potential economic impact on honey locust seed production. Subject of research investigating -based management strategies. Model organism for studying insect cold and range expansion.

Similar Taxa

Other Bruchinae seed beetlesSimilar and seed-feeding ; requires examination or molecular identification for differentiation
Acanthoscelides obtectusCommon bean weevil with similar body plan; distinguished by association and antennal structure

More Details

Cold tolerance physiology

employ freeze-avoidant strategy with supercooling point of -10.62°C and lower lethal temperature of -19.48°C at 28°C acclimation. Cold acclimation at 15-25°C significantly depresses supercooling point and freezing point compared to control. Cryoprotectants include glycerol and lipids, with water content reduction under prolonged cold exposure.

Invasion history

First European record Italy 1989. Slovenia first recorded 2017 with subsequent establishment confirmation at 36 locations (97% pod rate). Rapid range expansion across Europe facilitated by widespread ornamental planting of Gleditsia triacanthos.

Host range plasticity

Strict oligophagy on Caesalpinioideae in native range (Gleditsia ). Demonstrated switch to phylogenetically related Gymnocladus dioica (Umtiza clade) in introduced Central European range, representing significant diet breadth expansion.