Opilionida (Opiliones, Phalangida, including Cyphophthalmi)

Common names:  harvestmen, opilionids, daddy-long-legs

Probability of encounter: high

Quarantine importance: no known importance. 

Similarity to mites: some groups very mite-like, especially in dorsal view where the body may appear unsegmented.  However, at least the venter of the opisthosoma should be clearly segmented, even in immatures.

Morphology
 
Normal adult length: <15 mm
Body tagmata: prosoma, opisthosoma (but superficially appears as one body mass)
Eyes: 1 + 1 ocelli on median turret (or blind)
Antennae: absent
Mouthparts: 3-segmented chelicerae; leg-like or raptorial palps
Legs: 4 pairs; legs I or legs II antenniform
Distinguishing features: eye turret; repugnatorial glands; particulate feeding

Diversity: ca. 5,000 species.

References

Edgar, AL. 1990. Opiliones (Phalangida). pp. 529-581, in DL Dindal (ed) Soil Biology Guide. John Wiley & Sons: Brisbane.