Tetranychus gigas Pritchard & Baker

Návia, Denise & Flechtmann, Carlos H. W., 2004, Rediscovery and redescription of Tetranychus gigas (Acari, Prostigmata, Tetranychidae), Zootaxa 547, pp. 1-8 : 2-7

Tetranychus gigas Pritchard & Baker

Tetranychus gigas Pritchard & Baker, 1955:405 .

Redescription

FEMALE (n = 18) — Idiosoma 368–563 long, 555–675 including rostrum, 280–431 wide. Colour in life carmine red.

Prodorsal striation longitudinal; opisthosomal striae longitudinal between setae e1 and e1 and again between setae f1 and f1, forming a diamond shaped pattern. Peritremes distally hooked. ( Fig. 1 ).

Palp tarsus: terminal eupathidium (spinneret) 6 long and 4.5 in diameter; two lateral eupathidia 6 and 7 long; solenidion 6 long. ( Fig. 7 ).

Prodorsal setae slender, barbed; length v2 64 –79, sc1 124–158, sc2 94–113. Distances between setal insertions: v2–v2 60 –75, sc1–sc1 83–94. Hysterosomal setae long, pubescent. Setal length: c1 116–150, c2 113–143, c3 101–124, d1 113–139, d2 113–139, e1 113–131, e2 113–143, f1 98–128, f2 79–101, h1 38–49. Distances between setal insertions: c1–c1 56–79, d1–d1 98–109, e1–e1 113–131, f1–f1 34–75.

Legs: tarsus I with proximal duplex setae located at level ( Fig. 4 ) or about level ( Fig. 5 ) with the four proximal tactile setae. Empodia of tarsi I–IV with a small mediodorsal spur, visible in a perfect lateral view, less than one third the length of the proximoventral hairs. ( Figs. 8–11 ).

Leg chaetotaxy, from coxae to tarsi (solenidia in parentheses; numbers in brackets represent an alternative setal count observed in a few specimens)

I — 2­1 ­9[10]­5­9(1)­13(1) + 2 duplexes

II — 2­1 ­7[6]­5­7[8]­13(1) + 1 duplex

III — 1­1 ­4­4[3]­7­9(1)

IV — 1­1 ­4[3]­ 4­7­10 (1)

Ventral idiosoma transversely striated; area immediately anterior to genitalia with longitudinal broken striae. ( Fig. 6 ).

µm MALE (n = 10) — smaller than female, 366–484 long, including rostrum. Palptarsus terminal eupathidium (spinneret) 5 long and 2.6 in diameter; two lateral eupathidia 5 and 6 long; solenidion 4.5 long. ( Fig. 18 ).

Leg chaetotaxy, from coxae to tarsi (solenidia in parentheses)

I — 2­1­10­5­9 (4)­13(2) + 2 duplexes

II — 2­1 ­6­5­7­13(1) + 1 duplex

III — 1­1 ­4­4­6­9(1)

IV — 1­1 ­4­4­7­10(1)

Empodium I with a strong proximoventral, tapering tooth and, on each side, with a finer tooth on each side; mediodorsal spur strong and nearly as long as the trifid appendage. Empodium II with a strongly developed mediodorsal spur; empodia III and IV each with the mediodorsal spur small but obvious. ( Figs. 14–17 ).

Aedeagus shaft short, gradually narrowing and turning dorsad at a wide (obtuse) angle, ending in a larger knob. A neck is virtually absent. Aedeagal knob about as long as dorsal margin of shaft with the anterior angulation acute and caudal angulation acutely curved ventrad. Dorsum of knob rounded ( Fig. 19 ). Pritchard & Baker (1955) describe and figure a longer dorsal margin of the aedeagal shaft, however in the paratype specimen as well as in the Brazilian specimens we examined is much shorter.

We also examined one female and one male of a Tetranychus collected from beans, Phaseolus vulgaris L., in Piracicaba, São Paulo, Brazil, 5 Nov. 1971, coll. O. Nakano, which is considered to be very close to T. gigas . The male aedeagus is undistinguishable from that of T. gigas , but its tibia II has only 6 setae and tarsus IV 9 setae and one solenidion. The female is similar to that of T. gigas in the general aspect, differing in having 6 setae on tibia III and mainly in the much longer dorsal opisthosomal setae: c1 225, c2 210, c3 195, d1 225, d2 210, e1 206, e2 210, f1 180, f2 105 and in the wider distances between their bases: c1–c1 113, d1–d1 165, e1–e1 101 and f1–f1 105. Tarsal appendages have also the same aspect as those of T. gigas .

Figures

FIGURE 1: Tetranychus gigas Pritchard & Baker, female. Dorsal view.

FIGURES 6 – 11: Tetranychus gigas Pritchard & Baker, female. 6. Genitoanal region; 7. Palp tibia and tarsus; 8 – 11. Tarsal appendages of legs I – IV, in this sequence.

FIGURES 2 – 5: Tetranychus gigas Pritchard & Baker, female. 2. Tibia and tarsus I; 3. Tibia and tarsus II; 4. Basal part of tarsus I showing proximal duplex seta perfectly in line with four proximal tactile setae; 5. Basal part of tarsus I with duplex seta lying in a tangent with an immaginary circumsegmental ring through bases of proximal tactile setae.

FIGURES 12 – 19: Tetranychus gigas Pritchard & Baker, male. 12. Tibia and tarsus I; 13. Tibia and tarsus II; 14 – 17. Tarsal appendages of legs I – IV, in this sequence; 18. Palp tibia and tarsus; 19. Aedeagus.