Mastophora hutchinsoni

Distinguished from other orb-weavers by the absence of a typical two-dimensional orb web; females construct only a single horizontal thread with a terminal adhesive bolas. The extreme sexual dimorphism separates females from males—females are large with globular white-and-brown abdomens, males are small and reddish-brown. Distinguished from other Mastophora species by geographic range (northeastern North America) and specific pheromone mimicry targeting Noctuidae and Pyralidae moths. Egg sacs are identifiable by their spherical shape with extended stems, black-and-white mottled appearance, and attachment to twigs or branches.

Adult females possess a large spherical abdomen with milky white base coloration overlaid with darker brown patterns, combined with a smaller brown carapace. The globular abdomen serves as defensive camouflage, resembling bird droppings on leaves. Males are dramatically smaller, with reddish-brown coloration, and retain bristles on their front legs that females lose after maturation. Both sexes hatch with cephalothorax length around 0.5 mm, but females develop into significantly larger specimens. Egg sacs are spherical with extended stems up to 36 mm long, surrounded by protective layers and off-white silk, with globose vessels approximately 8 mm in diameter.

Occupies shrubs and short trees, particularly hackberry (Celtis sp.) in observed populations. Females position themselves at the crown (outer canopy near sun leaves) or internally (inner canopy near shade leaves), constructing bridge threads between leaf tips or branches. Frequently relocates by riding wind-borne silk threads to follow prey availability. Utilizes leaf undersides or upper leaf surfaces with silk splatter as daytime hiding spots.

Eastern North America, ranging from Minnesota to New Hampshire in the northeastern United States. One of five Mastophora species documented from the United States. Absent from western North America, where M. cornigera occurs instead.

Univoltine with distinct phenological stages: spiderlings emerge in May; males mature late June to early July; females mature early September; eggs produced from late September to early November; overwinters in egg stage. Adult females hunt nocturnally, emerging at sunset and remaining active until approximately 10:30 p.m. or later, with hunting periods shifting to match activity patterns of different moth species throughout the night.

Adult females exclusively capture male moths using bolas technique, primarily two Noctuidae species: bristly cutworm (Lacinipolia renigera, comprising two-thirds of prey biomass) and smoky tetanolita (Tetanolita mynesalis), together accounting for 93% of 492 documented prey captures; also bronzed cutworm (Nephelodes minians) and bluegrass webworm (Pyralidae). Spiderlings and adult males capture small arthropods—spiderlings ambush crawling prey on leaf margins using bristled front legs, while males retain similar hunting tactics and prey on psychodid flies.

• bristly cutworm moth (Lacinipolia renigera) - preyPrimary prey species; active soon after nightfall
• smoky tetanolita moth (Tetanolita mynesalis) - preySecondary prey species; active between 11:00 p.m. and dawn
• bronzed cutworm moth (Nephelodes minians) - preyTertiary prey species
• bluegrass webworm moth (Pyralidae) - preyMinor prey component
• hackberry (Celtis sp.) - habitatObserved hunting substrate in Kentucky populations

Univoltine annual cycle: eggs laid in spherical sacs with extended stems, attached to twigs or branches; overwintering occurs in egg stage; spiderlings emerge in spring (May); males develop rapidly, reaching maturity by late June to early July; females develop more slowly, maturing in early September; after maturation gap, males leave their webs and reside in webs of developing females to await mating; eggs produced from late September through late October or early November.

Adult females exhibit four distinct behavioral states: questing without bolas, creating bolas and questing with it, capturing moth with bolas, and consuming prey. Constructs solitary capture strand with single large glue droplet (approximately 2 mm diameter) containing coiled 'windlass' thread; flicks bolas at hovering moths after detecting wing vibrations via leg hairs. Glue droplet exhibits spring-like elastic behavior, stretching during flick and recoiling to spherical shape when missed. Consumes and replaces bolas after each use due to short-term adhesive efficacy. Employs aggressive chemical mimicry by synthesizing and releasing precise ratios of moth sex pheromone components to attract specific male moth species; adjusts pheromone blend throughout evening to target different moth species during their respective activity periods. Spiderlings and males use ambush predation rather than bolas technique.

Specialized predator of specific male moth species, with potential influence on moth mating dynamics through chemical mimicry that intercepts males seeking mates. Defensive bird-dropping mimicry reduces predation pressure on females. Movement by wind-borne silk may contribute to population dispersal and gene flow.

Venom not dangerous to humans or large animals; egg sacs sometimes mistaken for plant structures or insect cocoons. Subject of scientific research on chemical ecology, biomaterials, and specialized predatory adaptations. No documented economic importance or pest status.

• Mastophora cornigeraOnly other Mastophora species in United States; distinguished by western North American distribution (California and southwestern states) versus northeastern range of M. hutchinsoni
• Cyrtarachne akiraiAnother moth-specialist spider in subfamily Cyrtarachninae; distinguished by different bolas material properties—M. hutchinsoni produces thicker, more elastic glue with spring-like behavior versus less elastic bolas of C. akirai
• Typical Araneidae orb-weaversConstruct two-dimensional orb webs rather than single bolas; lack chemical mimicry of moth pheromones; do not exhibit extreme sexual dimorphism in hunting behavior

• bolas spider
• chemical mimicry
• sexual dimorphism
• pheromone mimicry
• moth predator
• nocturnal
• specialized predator
• orb-weaver

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bug Spotlight | Entomology Research Museum
• Botanizing at Meramec State Park, Natural Wonders Trail | Beetles In The Bush
• Behavior and Bioadhesives: How Bolas Spiders, Mastophora hutchinsoni, Catch Moths
• Ecology of a bolas spider, Mastophora hutchinsoni: phenology, hunting tactics, and evidence for aggressive chemical mimicry