Lygaeus kalmii

Stål, 1874

Small Milkweed Bug, Common Milkweed Bug

Lygaeus kalmii is a in the Lygaeidae known for its bright orange-red and black aposematic coloration. measure 10–12 mm and feed primarily on milkweed seeds and flower nectar, though they exhibit dietary flexibility including scavenging on dead insects and feeding on seeds of other plants such as composites. The sequesters cardiac glycosides from milkweed, making it unpalatable to . Unlike the migratory large milkweed bug (Oncopeltus fasciatus), L. kalmii is non-migratory and overwinters as adults. Two are recognized: L. k. kalmii in western North America and L. k. angustomarginatus in the east, distinguished by differences in the white markings on the membranous portion of the forewings.

Lygaeus kalmii by (c) Ken-ichi Ueda, some rights reserved (CC BY), uploaded by Ken-ichi Ueda. Used under a CC-BY license.Lygaeus kalmii - Small Milkweed Bug by CLK Hatcher. Used under a CC BY-SA 2.0 license.Mating Small Milkweed bugs Lygaeus kalmii by Wilson44691. Used under a CC0 license.

Pronunciation

How to pronounce Lygaeus kalmii: /laɪˈdʒiːəs ˈkælmi.aɪ/

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Identification

Distinguished from the similar False Milkweed (Lygaeus turcicus) by the red spot or vertical bar on the (L. turcicus has a Y-shaped marking) and by white markings on the black of the forewing (L. turcicus has few or none). The large milkweed bug (Oncopeltus fasciatus) is larger and has broader black bands across the forewings. The forewing pattern of L. kalmii—black inside an orange-red X—is diagnostic. identification requires examination of the white markings on the membranous forewing portion.

Images

Appearance

are 10–12 mm in length with orange-red and gray/black coloration. The is black with a distinct red spot or vertical bar in the center. The forewings display a characteristic pattern: a black shape inside an orange-red X that does not meet in the middle. The membranous portion of the forewings has white markings that differ between : L. k. angustomarginatus has a narrow white margin, while L. k. kalmii has white spots and a broader margin. Young nymphs are initially fully red, developing black diagonal markings on the pronotum as they mature.

Habitat

Associated with milkweed plants (Asclepias spp.) in diverse settings including sandy-grassy patches, bushy dry areas, and wet areas. have been observed in urban environments and vacant lots. The western occurs in dry bushy areas for feeding and wet areas for survival.

Distribution

North America and Central America. The eastern L. k. angustomarginatus occurs in north temperate regions of North America. The western subspecies L. k. kalmii ranges from Arizona (where it is very common) through California and adjacent areas.

Seasonality

overwinter and become active on warm winter days. begins in April. Adults are present year-round in mild climates, with peak abundance in summer and fall.

Diet

Primary food sources are milkweed seeds (Asclepias spp.) and flower nectar. When milkweed seeds are unavailable, individuals scavenge on assorted available seeds including composites such as asters. Documented feeding on oleander (Nerium oleander) seeds. Opportunistic scavenging on dead insects has been observed, including feeding on dead honeybees. on of the swamp (Labidomera clivicollis), monarch butterfly larvae and pupae, and insects trapped by milkweed pollinia has been reported.

Host Associations

  • Asclepias spp. - primary Seeds are primary food source for nymphs; feed on nectar
  • Asclepias fascicularis - Low cardiac glycoside content
  • Asclepias speciosa - High cardiac glycoside content
  • Asclepias tuberosa - weed, documented for feeding and
  • Asclepias incarnata - Swamp milkweed
  • Nerium oleander - Landscape plant in Arizona and elsewhere
  • Taraxacum officinale - Dandelion; some restricted to this when milkweed unavailable
  • Asteraceae - Composites such as asters, scavenged for seeds when milkweed unavailable

Life Cycle

are laid on milkweed in spring. Nymphs hatch and feed on milkweed seeds, developing through five instars. Nymphs initially red, developing black diagonal pronotal markings as they mature. Wing buds become visible and enlarge through successive . Only overwinter; does not begin until the following April. Females are receptive to males in all seasons.

Behavior

Non-migratory, in contrast to the large milkweed bug. overwinter in cracks and crevices, emerging on warm winter days. Exhibits correcting (righting response) when overturned. Mating pairs remain in copula for extended periods. Nymphs and adults insert their slender beak into seed pods to inject digestive and suck liquefied nutrients. Adults groom with forelegs.

Ecological Role

Seed on milkweeds and other plants. Member of the Müllerian mimicry complex of orange-and-black milkweed-feeding insects, including monarch butterfly, large milkweed bug, red milkweed beetles, milkweed leaf beetle, and milkweed assassin bug. Sequesters cardiac glycosides (cardenolides) from milkweed, storing them in specialized compartments along the and edges, rendering the distasteful or toxic to vertebrate predators and many predators.

Human Relevance

Not considered an agricultural pest. May be present in gardens and urban areas where milkweeds grow. Occasionally encountered by naturalists and photographers due to bright coloration. Serves as an example of aposematic coloration and chemical defense in educational contexts. Some have been studied for dietary flexibility and lack of -associated trade-offs.

Similar Taxa

Misconceptions

Despite , not an obligate milkweed ; exhibits dietary flexibility including scavenging and feeding on non-milkweed seeds. Not all have access to milkweed; some persist on dandelion and other without trade-offs. The does not undergo long-distance like the large milkweed bug.

More Details

Subspecies

Two recognized: L. k. kalmii Stål, 1874 (western small milkweed ) and L. k. angustomarginatus Parshley, 1919 (eastern small milkweed bug). Differ in white markings on membranous forewing portion.

Chemical Defense

Sequesters cardiac glycosides (cardenolides) from milkweed in specialized dorsolateral spaces; these poisons deter vertebrate and many predators.

Research History

Subject of studies by chemical ecologist Sean Duffey on cardiac glycoside mechanisms. Research has demonstrated lack of -associated trade-offs between milkweed- and dandelion-restricted .

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Sources and further reading