Acalymma

Barber, 1947

striped cucumber beetles, cucumber beetles

Species Guides

6

Acalymma is a of leaf beetles in the Chrysomelidae comprising approximately 72 described in the Western Hemisphere. The genus is primarily distributed in the New World, with most species occurring in North America including Mexico. Two species, A. vittatum (striped cucumber ) and A. trivittatum (western striped cucumber beetle), are major agricultural pests of cucurbit crops. Acalymma species are on plants in the family Cucurbitaceae, with feeding on leaves, flowers, and fruit, and larvae feeding on roots.

Acalymma vittatum by (c) Katja Schulz, some rights reserved (CC BY). Used under a CC-BY license.Acalymma by (c) Nick Block, some rights reserved (CC BY), uploaded by Nick Block. Used under a CC-BY license.Acalymma vinctum by no rights reserved, uploaded by kcthetc1. Used under a CC0 license.

Pronunciation

How to pronounce Acalymma: /əˈkalɪmə/

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Identification

Acalymma are distinguished from the related Diabrotica by genitalic and external morphological characters; males possess distinctive aedeagal structures used in species-level identification. The two most economically important species, A. vittatum and A. trivittatum, are separated geographically by the Rocky Mountains and can be distinguished by subtle differences in elytral striping patterns and genitalia. Species within the genus are generally small to medium-sized leaf beetles with elongated bodies and often exhibit striped or spotted color patterns on the .

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Habitat

Acalymma are associated with containing plants in the Cucurbitaceae. In natural settings, this includes forest edges, open patches, and areas where wild cucurbits occur. In agricultural systems, they are found in fields of cultivated cucurbits including cucumber, melon, squash, and pumpkin. Research on A. innubum in the Virgin Islands indicates that open, low-diversity patches with host plants support higher densities than forested, high-diversity habitats.

Distribution

The is distributed primarily in the New World, with approximately 72 described in the Western Hemisphere. The majority of species occur in North America, including Mexico, with some extending into Central America and the Caribbean. A. vittatum occurs east of the Rocky Mountains in North America, while A. trivittatum occurs west of the Rocky Mountains. The northern range extends to southern Canada, and the southern range extends through most of Mexico.

Seasonality

Activity patterns vary by and latitude. In temperate regions, overwinter and become active in spring when cucurbit become available. The number of per year ranges from one in northern latitudes to three in southern, warmer regions. peak in late summer. For A. vittatum, seasonal activity corresponds with cucurbit crop , with early-season of seedling plants.

Diet

Acalymma are on plants in the Cucurbitaceae. feed on leaves, cotyledons, stems, flowers, pollen, and fruit. Larvae feed on roots and stem bases below ground. Research indicates strong preference for bitter cucurbits containing cucurbitacin compounds, which act as feeding arrestants. A. vittatum shows highest feeding and oviposition preference for Cucurbita pepo (summer squash) among tested cucurbit species.

Host Associations

  • Cucurbitaceae (family) - herbivoreAll life stages specialized on this plant
  • Cucumis sativus - cucumber; major crop
  • Cucumis melo - cantaloupe, muskmelon; major crop
  • Cucurbita pepo - preferred summer squash, pumpkin; highest preference in feeding and oviposition trials
  • Cucurbita maxima - intermediate preference in trials
  • Cucurbita moschata - intermediate preference in trials

Life Cycle

Females lay in soil at the base of plants, with a single female capable of producing up to 1,500 eggs over her lifetime. Eggs hatch into larvae that feed on roots and pupate in soil. emerge from and disperse to host plants. The number of per year varies from one in northern regions to three in warmer southern regions. occurs as adults in protected locations.

Behavior

are strong fliers and readily disperse among fields during the growing season. Males produce an , vittatalactone, which facilitates early-season plant and aggregation on preferred crops. Beetles exhibit greater tenure time on host plants in compared to , and preferentially colonize open, sunny over shaded forest patches. by the tachinid fly Celatoria setosa reduces feeding, oviposition, and pheromone emission in A. vittatum.

Ecological Role

As herbivores on Cucurbitaceae, Acalymma influence plant and structure in both natural and agricultural settings. In natural communities, they contribute to herbivore pressure on wild cucurbits and are affected by plant diversity and patch size. In agricultural systems, they function as significant pests and of plant . They serve as for including Celatoria setosa and Centistes diabroticae, which provide services.

Human Relevance

Two , A. vittatum and A. trivittatum, are major agricultural pests causing significant economic damage to cucurbit crops. Damage includes direct feeding injury to seedlings, leaves, flowers, and fruit, as well as transmission of bacterial wilt caused by Erwinia tracheiphila. A. vittatum also squash mosaic virus and fungal causing Fusarium wilt and black rot. The male-produced vittatalactone is used in monitoring and has potential for management through attract-and-kill strategies. Management relies on , , cultural practices, and , though resistance development and non-target effects on are concerns.

Similar Taxa

More Details

Taxonomic revision

The of Acalymma sensu stricto were revised by Munroe and Smith (1980), who defined the and distinguished it from other groups within the former broader concept of Acalymma. The revision included 16 species with descriptions of four new species from Mexico and three new of A. blandulum.

Chemical ecology

The vittatalactone, produced by male A. vittatum, has been shown to attract both A. vittatum and A. trivittatum, as well as the spotted cucumber beetle Diabrotica undecimpunctata, suggesting potential for cross- monitoring and management applications.

RNAi potential

Transcriptome sequencing of A. vittatum has identified numerous sex-specific and xenobiotic detoxification genes, including glutathione S-transferases, carboxylesterases, and P450 monooxygenases, providing potential targets for interference-based biocontrol approaches.

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