Longistigma

Distinguished from other aphid genera by the extremely elongated stigma that curves around the wing tip, the characteristic that gave the genus its name. Adults are notably large for aphids, with some individuals reaching sizes far exceeding typical aphid dimensions. Winged and wingless morphs occur within colonies. The combination of large body size, bark-feeding habit on hardwood trees, and distinctive wing venation with elongated stigma separates Longistigma from other Lachninae.

Associated with bark of hardwood trees including oak (Quercus), hickory (Carya), walnut (Juglans), and beech (Fagus). Found on branches and trunks of mature trees, often on leafless branches during late autumn and winter.

North America; records from Massachusetts, Illinois, and other eastern and central United States. One species, Longistigma xizangensis, described from Tibet (Xizang), China.

Active during growing season; colonies observed into late autumn. Overwintering occurs as eggs deposited on branches. In late autumn, females switch from viviparous reproduction to laying eggs that persist through winter and hatch when trees become sappy in spring.

Phloem sap from bark of hardwood trees. Feeding occurs on branches through elongated mouthparts.

• Carya glabra - hostpignut hickory; original description host
• Quercus - hostoak species
• Juglans - hostwalnut species
• Fagus - hostbeech species

Reproduction is parthenogenetic and viviparous during the growing season, with females giving birth to live nymphs. As temperatures decline in autumn, females transition to oviparity, depositing eggs on branches by the thousands. Eggs serve as the overwintering stage, changing from amber to black as they age. Eggs hatch in spring when host trees resume sap flow.

Forms colonies on bark of host trees. Engages in mutualistic relationships with ants, which tend the aphids and receive honeydew in exchange for protection from predators and parasites. This ant-aphid mutualism has been observed in multiple countries.

Primary consumer feeding on plant phloem; converts plant sap into biomass that supports ant mutualists and other consumers. Honeydew production provides energy source for ants and potentially other insects. Serves as prey for various predators and parasitoids, though ant attendance provides protection.

Primarily of ecological and entomological interest due to remarkable size. Not considered a major economic pest, though heavy infestations may occur. Subject of natural history observation and educational interest, particularly around holiday seasons when colonies are visible on leafless trees.

• TuberolachnusTuberolachnus salignus (giant willow aphid) is comparable in large size and bark-feeding habit, but occurs on willow (Salix) rather than hardwood trees, and lacks the elongated stigma characteristic of Longistigma
• CinaraOther large aphids in subfamily Lachninae, but distinguished by host associations, body proportions, and wing venation details

• aphid
• giant aphid
• bark feeder
• parthenogenesis
• ant mutualism
• viviparity
• overwintering eggs
• hardwood forest
• phloem feeder
• Sternorrhyncha

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• ‘Twas two weeks before Christmas – Giant bark aphids, Longistigma caryae and giant willow aphids, Tuberolachnus salignus — Bug of the Week
• ‘Twas the week before Christmas: Giant bark aphids, Longistigma caryae, and giant willow aphids, Tuberolachnus salignus — Bug of the Week
• 'Twas two weeks after Christmas - Giant bark aphids, Longistigma caryae — Bug of the Week
• ‘Twas the week before Christmas: Giant bark aphids, Longistigma caryae, and giant willow aphids, Tuberolachnus salignus — Bug of the Week
• Archive — Bug of the Week
• Giant Bark Aphid, Longistigma caryae (Harris) (Insecta: Hemiptera: Aphididae)