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Fig. 1. Oligonychus araneum adult female - dorsal habitus.

Fig. 2. Oligonychus araneum adult female - detail of empodia.

Fig. 3. Oligonychus araneum adult female - detail of pattern of pregenital striae.

Fig. 4. Oligonychus araneum adult female - detail of peritreme (arrows indicate bulb at tip).

Fig. 5. Oligonychus araneum adult female - detail of pattern of dorsal striae between setae e1 and f1.

Fig. 6. Oligonychus araneum adult female - detail of pattern of dorsal striae between setae e1 and f1.

Fig. 7. Oligonychus araneum adult female - detail of tarsus I (indicating number of setae proximal to the duplex setae).

Fig. 8. Oligonychus araneum adult male - detail of empodium I (left) and IV (right).

Fig. 9. Oligonychus araneum adult male - detail of empodia.

Fig. 10. Oligonychus araneum adult male - detail of peritreme (arrow indicates simple bulb).

Fig. 11.   Oligonychus araneum adult male - detail of aedeagus (arrow indicates curved tip).

Material examined

types

Taxonomy

Subfamily Tetranychinae

Tribe Tetranychini

Distribution

*Australia: south eastern Queensland, New South Wales

Taxonomy Changes

None

Diagnosis

Female (Fig. 1)

• empodia I-IV long slender claw (Fig. 2)
• pregenital striae oblique, irregular (Fig. 3)
• peritreme ending in simple bulb with little or no expansion (Fig. 4)
• most dorsal striae transverse, except irregular longitudinal and oblique between opisthosomal setae f1 and f2 (Figs 5, 6)
• lobes on dorsal striae small, semicircular, some almost oblong, closely spaced (Fig. 6) 
• lobes on ventral striae small, rounded, widely spaced
• tarsus I with the sockets of four tactile setae proximal to the socket of the proximal duplex seta (Fig. 7) 
• chaetotaxy of legs I-IV (bold numbers are considered the normal value):
  • femora 10, 6, 3/4, 3/4
  • genua 5, 5, 4, 4
  • tibiae 9-10(1+0), 6-7, 6, 7
• pale green or yellowish with dark spots along sides of body
• copious webbing produced

Male

• empodium I = bifid claw, ventral spur longer than dorsal spur (Fig. 8)
• empodia II-IV with dorsal claw shorter than proximoventral hairs (Figs 8, 9)
• peritreme ending in simple bulb with little or no expansion (Fig. 10)
• tarsus I with sockets of four tactile and two-three sensory setae proximal to the socket of the proximal duplex seta
• chaetotaxy of legs I-IV: 
  • femora 10, 5, 4, 4
  • genua 5, 5, 4, 4
  • tibiae 12-13(3-4+0), 7 -8, 6, 7
• aedeagus dorsally directed, abruptly bent dorsally, tapering, very tip curved posteriorly (Fig. 11)

Hosts

*Cynodon dactylon, *Digitaria didactyla, *Pennisetum clandestinum, *Stenotaphrum secundatum (Poaceae)

Similar Taxa

Oligonychus digitatus Davis 1966

Oligonychus plegas Baker & Pritchard 1960

Oligonychus velascoi Rimando 1962

Biology

Recorded as a pest of grasses in eastern Australia.  Oligonychus araneum can occur in very large populations that cause yellowing of grass in a ring-shaped area as the colony grows and spreads outwards from the initial infestation which turns brown (Davis 1968).  The species spins copious amounts of webbing.

Oligonychus araneum often occurs with O. digitatus.

References

*Davis, J.J. (1968d)  Oligonychus araneum sp. n. and Oligonychus digitatus Davis (Acarina: Tetranychidae) as pests of grasses in eastern Australia.  Journal of the Australian Entomological Society 7: 123-126