Picromerus bidens

(Linnaeus, 1758)

spiny shieldbug, spiked shieldbug

Picromerus bidens is a predatory in the , notable for its large size and distinctive spiny pronotal projections. It is , with () ensuring synchronization of its with seasonal conditions. The is to the Palaearctic region but has been to North America, where it has established . Both and are predatory, feeding primarily on , and the species has been investigated as a potential agent.

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Shield bugs, Picromerus bidens - geograph.org.uk - 2092577 by Lairich Rig . Used under a CC BY-SA 2.0 license.

Pronunciation

How to pronounce Picromerus bidens: /pɪˈkroʊmɛrəs ˈbaɪˌdɛnz/

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Identification

Distinguished from other by the two prominent thornlike projections on the . The combination of large size (12–13.5 mm), variable to bluish coloration, red-brown appendages, and the distinctive 'spiny' pronotum separates it from and other . Final can be recognized by their greyish black coloration with banded and legs.

Images

Habitat

Deciduous and mixed forests, heathland, gardens, chalk downland, and damp flower-rich meadows. In North America, has been recorded from more than 180 sites across varied .

Distribution

to the Palaearctic region, ranging from 64°N to North Africa and from the British Isles to China. to North America, probably on multiple occasions, with established recorded from more than 180 sites.

Seasonality

present from July or August until November. become adults by July or August. laid on tree trunks and leaves; hatch in spring. usually overwinters as eggs, less frequently as nymphs.

Diet

Both and are predatory, feeding on of other including leaf (), , , and . selection depends on season and availability. Adults and nymphs have also been observed sucking sap from plants.

Life Cycle

(one per year). Females lay on tree trunks and leaves. hatch in spring and develop through five moults to become by July or August. () in early-emerging adults prevents early and maintains univoltinism. occurs primarily as eggs, less commonly as .

Behavior

Exhibits () induced by long-day photoperiodic conditions, which delays and prevents untimely hatching of . When attacking in protective silken webs, exhibit efficient including returning to previously attacked webs. varies with temperature and context.

Ecological Role

of , including agricultural and forest pests. Can act as a substantial mortality factor in small insect . Investigated as a potential agent for defoliating and the ().

Human Relevance

Investigated as a agent for pest , particularly as a potential alternative to the North Podisus maculiventris in Europe. High rates at varied temperatures suggest value for biological control, though mass production obstacles remain. Climate change may reduce suitable , potentially limiting its effectiveness as a agent.

Similar Taxa

Podisus maculiventrisBoth are predatory used in ; P. bidens has longer nymphal development and greater voracity at temperature extremes, while P. maculiventris has higher rates at moderate temperatures.

More Details

Photoperiodic Response

Long-day conditions (L18:D6, L20:D4) induce , delaying ; short-day conditions (L12:D12, L14:D10) result in synchronous -laying soon after .

Functional Response

Exhibits II at 18°C and 23°C, but type III response at 27°C; and vary significantly with and temperature.