Mastophora

Holmberg, 1876

bolas spiders, American bolas spiders

Species Guides

8

Mastophora is a of orb-weaver spiders in the Araneidae, commonly known as bolas spiders. These spiders have abandoned the typical orb-web construction of their relatives and instead hunt using a unique method: they produce a single droplet of sticky silk suspended on a thread (the "bolas") and swing it to capture flying prey. females are that use aggressive chemical mimicry, releasing to attract specific male moth within range of their bolas. The genus includes 15 species in the United States, with Mastophora cornigera being the only species found in California.

Mastophora hutchinsoni by (c) Ken-ichi Ueda, some rights reserved (CC BY), uploaded by Ken-ichi Ueda. Used under a CC-BY license.Mastophora stowei by (c) Andy Deans, some rights reserved (CC BY), uploaded by Andy Deans. Used under a CC-BY license.Mastophora cornigera by (c) Millie Basden, some rights reserved (CC BY), uploaded by Millie Basden. Used under a CC-BY license.

Pronunciation

How to pronounce Mastophora: //mæˈstɒfərə//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

females can be recognized by their cryptic, bird-dropping-like coloration with light streaks mimicking deposits. They possess a pair of lumps on the surface of the opisthosoma (). Males are diminutive and emerge from sacs as penultimates, undergoing only one before maturity, making them much smaller than females. Egg sacs are black and white mottled and often provide the first clue to a spider's presence, as the spiders themselves hide during daylight hours.

Images

Habitat

hunters that hide during daylight on the underside of leaves or camouflaged on upper leaf surfaces with silk splatter. females hunt in open areas, positioning themselves at tree crowns or internally within foliage. Specific hunting substrates include hackberry trees (Celtis sp.) in farmland and fence line areas. Spiderlings position themselves on leaf margins.

Distribution

occurs in the Americas. Fifteen in the United States; Mastophora cornigera is the only species in California. Eastern North American species (e.g., M. hutchinsoni) studied in Kentucky. One Central American species, M. dizzydeani, named for its spinning .

Seasonality

(one per year) in temperate regions. Spiderlings emerge in May; males mature late June to early July; females mature early September; produced late September to early November.

Diet

females exclusively prey on male , specifically few Noctuidae (bristly cutworm, bronzed , smoky tetanolita) and one Pyralidae species (bluegrass webworm). Two species (smoky tetanolita and bristly cutworm) accounted for 93% of 492 prey captured in one study. Spiderlings prey on small arthropods crawling along leaf margins, specifically male humpbacked flies (Phoridae).

Life Cycle

Overwinters in stage. Spiderlings emerge in May and use ambush hunting on leaf margins. Late-stadia and females transition to bolas hunting technique. Males mature earlier than females (protandry).

Behavior

; emerges from hiding at sunset, activity typically ends by 10:30 p.m. Creates solitary capture strand with one large glue droplet (bolas) containing coiled 'windlass' thread. Flicks bolas at approaching prey while dangling from one leg. Exhibits aggressive chemical mimicry: produces compounds mimicking of specific male . Can alter blend throughout evening to match different moth species active at different times (bristly cutworm soon after nightfall, smoky tetanolita between 11:00 p.m. and dawn). Glue droplet exhibits spring-like viscoelastic , stretching during flicking and rebounding to spherical shape when missing.

Ecological Role

of male ; part of Cyrtarachninae that evolved specific adaptations to defeat moth anti-predator defenses (sacrificial that normally allow moths to escape typical orb webs). May influence moth mating dynamics through selective on males attracted to mimics.

Similar Taxa

  • Cyrtarachne akiraiAnother - spider in Cyrtarachninae that uses modified orb-web structure, but Mastophora has evolved further to use a single bolas thread rather than any web structure; glue material properties also differ
  • Cladomelea debeeriSouth African bolas spider with similar hunting technique, but in a different ; Mastophora is restricted to the Americas

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Sources and further reading