Eupnoi

Eupnoi can be distinguished from other harvestman suborders by the combination of long legs (particularly in Phalangioidea), the presence of a dorsal ozopore associated with a unique secretory gland, and the absence of the heavily armored, short-legged morphology characteristic of Laniatores. From Dyspnoi, they differ in leg proportions and genetic relationships. Caddoidea are distinguished from Phalangioidea by their prominent eyes and spiny pedipalps. Species-level identification relies on characters including ocularium structure, penis morphology, pedipalp armature, and cuticular microanatomy; traditional characters such as body length and leg segment ratios are often unreliable.

Eupnoi harvestmen display the classic harvestman body plan with a fused prosoma and opisthosoma forming an oval to elongated body, and characteristically long, slender legs. Phalangioidea species typically have extremely elongated legs, particularly the second pair, which are often waved in the air as sensory appendages. Caddoidea species possess prominent eyes and conspicuously spiny pedipalps. All Eupnoi have an ocularium (eye tubercle) bearing the eyes, and a dorsal ozopore opening from a unique secretory gland. Cuticular surface texture and setal distribution vary considerably among species and may include tubercles, spines, or smooth areas.

Eupnoi occupy diverse habitats across their broad distribution. Phalangioidea species are common in wooded habitats, forest edges, and grasslands, with many species favoring moist microhabitats under logs, stones, and leaf litter. Caddoidea are found in temperate zones of both hemispheres, including forests in Japan, southern South America, Venezuela, New Zealand, and Australia. Sclerosomatidae subfamilies show distinct habitat preferences: Leiobuninae range across the Holarctic into montane regions; Gagrellinae inhabit Indo-Malayan and neotropical forests; Gyinae occur at high elevations in the Caucasus, Alps, and Nepal. Many species form traditional roosting aggregations in sheltered locations.

Eupnoi have a global distribution spanning all continents except Antarctica. Phalangioidea are particularly diverse and abundant in northern temperate regions. Caddoidea occur in temperate zones of both hemispheres, with records from Japan, North America, southern South America, Venezuela, New Zealand, and Australia; Baltic amber contains 40-million-year-old Caddoidea fossils. Neopilionidae exhibit a Gondwanan distribution (South America, South Africa, Australia). Sclerosomatidae display complex biogeographic patterns: Leiobuninae across the Holarctic to Costa Rica; Gagrellinae in Indo-Malayan and neotropical regions; Sclerosomatinae restricted to the Palearctic. Phalangiidae show Mediterranean-centered diversity with some introduced Nearctic populations.

Activity patterns vary by species and climate. Temperate species are typically active during warmer months, with some species forming aggregations during cooler periods. Specific seasonality data not documented at suborder level.

• Leptus (Erythraeidae) - ectoparasiteLarval mites parasitize harvestmen, attaching primarily to leg femora; prevalence and intensity vary with host species and habitat quality

Eupnoi harvestmen exhibit sophisticated chemical communication mediated by their unique dorsal secretory gland. They rely on short-range olfaction and contact chemoreception using specialized setae. Documented behaviors include: defensive secretion release; alarm signaling potentially involving pheromones; spatial marking of traditional roosting sites; recruitment to aggregations; and chemical communication during courtship. The second pair of legs is frequently waved in the air as pseudo-antennae to detect stimuli. When disturbed, individuals may exhibit thanatosis (playing dead) or voluntarily autotomize legs as additional defense mechanisms.

Eupnoi serve as prey for various predators and as hosts for ectoparasitic mites. Their aggregations may influence local arthropod community structure. As generalist predators and scavengers, they contribute to nutrient cycling and prey on small invertebrates, though specific ecosystem functions are poorly documented. Mite parasitism intensity on Eupnoi has been proposed as an indicator of habitat quality in forest ecosystems.

Eupnoi harvestmen are familiar to the public as "daddy long-legs" and are generally considered harmless. They are common subjects in macrophotography due to their accessibility and distinctive appearance. Some introduced species (e.g., certain Phalangiinae in the Nearctic) have expanded their ranges with human activity. The group has received significant research attention for their unique chemical communication systems and as models for studying arthropod social behavior and aggregation.

• DyspnoiTraditionally grouped with Eupnoi as Palpatores; differs in leg proportions and recently proposed as sister to Laniatores rather than to Eupnoi; includes genera with enlarged chelicerae for crushing snail shells (e.g., Ischyropsalis, Nipponopsalis) not found in Eupnoi
• LaniatoresShort-legged, heavily armored harvestmen with enlarged pedipalps for predation; lacks the long-legged, ozopore-bearing morphology of Eupnoi; generally more robust and less cursorial
• CyphophthalmiMite-like, eyeless harvestmen lacking ocularium; extremely small and cryptic; no chemical defense glands comparable to Eupnoi ozopore system

• harvestmen
• daddy long-legs
• chemical communication
• aggregation behavior
• defensive secretion
• ozopore
• Gondwanan distribution
• temperate fauna

• BugGuide
• Wikipedia
• iNaturalist taxon
• Catalogue of Life
• Answer to Super Crop Challenge #1 | Beetles In The Bush
• Chemical communication and ecology in Eupnoi harvestmen
• Comparative Study of the Microanatomy of Four Species of Harvestmen (Opiliones, Eupnoi)
• Distribution of 18S rDNA clusters in Central European harvestmen of the suborder Eupnoi (Arachnida: Opiliones)
• Contrasting patterns of divergence and gene flow in subspecies of a forest-dwelling harvestman Leiobunum japanense (Eupnoi: Opiliones: Arachnida)
• Host–parasite interactions between mites (Acari: Erythraeidae) and harvestmen (Opiliones, Eupnoi) as indicators of habitat quality in the Atlantic Forest
• Taxonomic notes on Holcobunus Roewer, 1910, with descriptions of three new species, and new records for Holcobunus nigripalpis Roewer, 1910<br />(Opiliones: Eupnoi: Sclerosomatidae)