Otobius megnini

Distinguished from hard ticks (Ixodidae) by the absence of a scutum and the ventral position of mouthparts. The spinose nymphal stage is diagnostic compared to other Otobius species. In ear canal infestations, identification is supported by the location deep within the external auditory canal and the presence of multiple life stages simultaneously due to the extended nymphal residence period.

Soft-bodied tick lacking a scutum. Nymphs are somewhat violin-shaped and covered with tiny backward-projecting spines, giving the species its common name. Adults reach approximately 10 mm in length, are brown in coloration, and possess a slightly granular body cuticle. Males and females are similar in appearance. Mouthparts are not visible from the dorsal view, located beneath the body typical of soft ticks.

Larval and nymphal stages occupy the external ear canals of definitive hosts. Free-living adults and engorged nymphs exiting hosts seek dry, protected microhabitats such as cracks and crevices in stable structures, beneath logs, or under fence posts. The species is generally associated with semiarid to arid environments but has expanded to other climates through animal transportation.

Worldwide distribution. Documented from North America, South America (Argentina, Bolivia, Brazil, Chile, Colombia, Peru, Venezuela), Central America (Cuba, Guatemala, Mexico), Africa (Democratic Republic of Congo, Lesotho, Madagascar, Malawi, South Africa, Sudan, Zambia, Zimbabwe), and Asia (Sri Lanka). In the United States, particularly associated with the Southwestern region.

Larvae and nymphs are obligate blood-feeders. Adults do not feed; they absorb atmospheric water for survival.

• horses - primary hostFrequently infested; muscle spasms and colic reported in heavy infestations
• cattle - hostBos primigenius taurus confirmed
• sheep - host
• goats - host
• dogs - host
• humans - occasional hostSeveral cases of infestation reported
• South American camelids - hostArgentina records

Single-host lifecycle. Eggs hatch on or near ground in 18+ days. Unfed larvae climb vegetation or structures to quest for hosts and can survive >2 months without feeding. Upon host contact, larvae migrate to ears and feed for 5–10 days, then molt to nymphs within the ear canal. Nymphs feed for approximately one month and can remain in the ear for 1–7 months total. Engorged nymphs exit the host, molt to adults on the ground. Adults are free-living, non-feeding, and can produce eggs for up to 6 months. Multiple nymphal instars may be present simultaneously in host ears.

Larvae exhibit host-seeking behavior by climbing vertical surfaces. Nymphs remain sedentary within ear canals for extended periods. Adults actively burrow into substrate when seeking shelter. Heavy infestations cause hosts to shake heads, rub ears, and exhibit signs of intense irritation.

Veterinary parasite causing direct harm through blood loss, tissue damage, and secondary infections. Documented vector of Q fever (Coxiella burnetii). Serves as prey for ants (Tapinoma melanocephalum, Monomorium spp., Pheidole sp., Crematogaster sp.), which may act as bio-suppressors of non-parasitic stages.

Significant veterinary pest causing economic losses through reduced animal productivity, hide damage, and treatment costs. Rarely infests humans. Control relies on acaricides, ear tags, and environmental management of free-living stages.

• Ixodidae (hard ticks)O. megnini lacks the scutum characteristic of hard ticks and has ventrally positioned mouthparts
• Other Otobius speciesO. megnini distinguished by spinose nymphal integument and specific host association with ear canals
• Otobius lagophilusRabbit ear tick with similar ecology but different host specificity and geographic range

• tick
• soft tick
• ectoparasite
• ear parasite
• veterinary pest
• Argasidae

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Managing External Parasites of Texas Cattle - AgriLife Extension Entomology
• Muscle spasms associated with ear tick (Otobius megnini) infestations in five horses
• Ants as predators of the Spinose Ear Tick, Otobius megnini (Dugès) in Sri Lanka
• First Record of Otobius Megnini (Dugés, 1883) (Ixodida: Argasidae) Found on Bos Primigenius Taurus in San Juan Province, Argentina
• Seasonal dynamics of spinose ear tick Otobius megnini associated with horse otoacariasis in Sri Lanka
• Life cycle of Spinose ear tick, Otobius megnini (Acari: Argasidae) infesting the race horses in Nuwara Eliya, Sri Lanka
• Myotonia and Colic Associated with the Spinose Ear Tick, Otobius megnini, in a Horse in Northern Mexico
• Spatial and temporal distributions of the Spinose Ear Tick,Otobius megnini, within animal shelters at Fossil Rim Wildlife Center