Theridium eximius, LINEAGE

Agnarsson, Ingi, 2006, A revision of the New World eximius lineage of Anelosimus (Araneae, Theridiidae) and a phylogenetic analysis using worldwide exemplars, Zoological Journal of the Linnean Society 146 (4), pp. 453-593 : 478-479

THE EXIMIUS LINEAGE

Diagnosis: Males of the eximius lineage differ from other Anelosimus in having deeply notched cymbial margins ( Figs 23A, B , 29A , 33A ), a subterminally ridged theridiid tegular apophysis ( Figs 2B , 42C ), embolus-distal hematodocha grooves ( Figs 35B, H, L , 36C , 39B, C ) and from most species by a translucent cymbial hood. Females may be difficult to diagnose from other Anelosimus , most species (excluding the domingo group and A. eximius ) differ in having strongly sclerotized copulatory ducts. They differ from the closely related Madagascar group by lacking an epigynal septum, and the epigynal scape clade (including three other American species) by lacking a scape. Females differ from the rupununi group (including the remaining American species) by entire anterior epigynal bursa.

Description: Prosoma light orange or yellow, eye region pale orange with rest of cephalic area greyish. Narrow rim around the edge of prosoma slightly darker bearing a regular row of small thickened setae. Sternum extending between coxae IV ( Fig. 24D ). Sternum base colour (in alcohol) brownish-yellow, mostly covered by dusky gray dots, with a darker rim around edge and an indistinct brownish-yellow central streak. Labium separated by a seam ( Fig. 24D ). Abdomen light grey to bright red (dark in alcohol), with a dark grey dorsal longitudinal notched folium ( Fig. 7G ). Abdomen-prosoma stridulatory apparatus present. Colulus absent, but two colular setae present ( Fig. 31E ). Leg base colour pale yellow, femur, patella and distal tip of tibia and metatarsus covered with dusky grey dots. Two parallel pale yellow streaks distally on ventral side of femur I, may be only one streak or no streak on other femora. Pedipalp with a small outgrowth of tegulum – the subconductor – at base of a lamelliform conductor; theridiid tegular apophysis large, pointed, supporting embolus, attached to the tegulum via the distal hematodocha; median apophysis medially attached to the tegulum via the distal hematodocha, interacting with hood on cymbial margin, embolus large, usually bipartite (embolus plus the embolic division b) ( Fig. 19A, B, F, G, J–L ). Cymbium with a large tarsal organ, tip of cymbium weakly sclerotized, whitish in preserved specimens. Pedipalpal tibia cup shaped ( Fig. 2F ) with ventral side forming a lip with the characteristic theridiid row of very long setae ( Fig. 27B, C ).

Phylogenetics: The eximius lineage is the largest clade containing only New World species. The monophyly of the eximius lineage is supported by at least the following putative synapomorphies: deeply notched cymbial margin (15 -2, Figs 23A, B , 29A , 33A ), translucent cymbial hood (25 -0), an abrupt post-SBII turn of the sperm duct (30 -1, Fig. 57D–F ), subterminally ridged theridiid tegular apophysis (56 -1, Figs 2B , 42C ), and embolus-dh grooves (69 -1, Figs 35B, H, L , 36C , 39B, C ). The Madagascar group is sister to the eximius lineage .

Composition: The eximius lineage contains 20 species: A. analyticus , A. arizona , A. baeza , A. chickeringi , A. domingo , A. dubiosus , A. elegans , A. eximius , A. fraternus , A. guacamayos , A. jabaquara , A. jucundus , A. octavius , A. oritoyacu , A. pacificus , A. pantanal , A. puravida , A. studiosus , A. tosum and A. tungurahua .

Distribution: New World, from north-eastern USA to Argentina ( Fig. 63A ). Most speciose in Ecuador and Mexico, particularly at altitudes of 1000 m or above.

Natural history: All studied eximius lineage species are social; for an overview of the natural history of social species see under Anelosimus above.

Figures

Figure 2. Anelosimus analyticus, male palp. A, dorsal; B, submesal; C, ventral, note the small embolic division b (Eb), and the cymbial hood (upper arrow). In this species the embolic lobe fits snugly under the subconductor (SC); D, ectal; E, apical view of tip, mesal side; F, part of palpal tibia, unusually with four trichobothria (arrows). Scale bars: A–D, 100 µm; E,F, 50 µm.

Figure 7. The ‘domingo group’. A–D, Anelosimus domingo. A, male palp mesal; B, same ventral; C, epigynum; D, internal epigynum dorsal. E–J, Anelosimus jabaquara. E, male palp submesal; F, same ventral; G, female abdomen; H, male habitus; I, epigynum; J, internal epigynum dorsal. K–P, Anelosimus dubiosus. K, male palp mesal; L, same ventral; M, epigynum; N, internal epigynum dorsal; O, digital photograph of internal epigynum dorsal; P, male first leg.

Figure 19. The ‘jucundus group’. A–E, Anelosimus arizona. A, male palp mesal, arrow points to the eb-ridge, larger in this species than in any other Anelosimus; B, same ventral; C, epigynum; D, internal epigynum dorsal; E, female habitus. F–I, Anelosimus jucundus. F, male palp mesal; G, same ventral; H, epigynum; I, internal epigynum dorsal. J–N, Anelosimus octavius. J, male palp expanded, mesal; K, male palp ventral; L, male palp expanded, ectal; M, epigynum; N, internal epigynum dorsal.

Figure 23. Anelosimus jucundus, male palp. A, dorsal view; B, mesal; C, submesal, the conspicuous embolus division b ridge (arrow) is a synapomorphy uniting A. jucundus, A. octavius and A. arizona; D, ventral; E, ectal, subcaudal view; F, details of E tip, the small conductor can be detected in the background (arrow). Scale bars: 100 µm.

Figure 24. Anelosimus jucundus. A, epiandrous gland spigots; B, epigynum; C, male stridulatory pick row; D, female prosoma ventral; E, female prosoma dorsal; F, male prosoma dorsocaudal. Scale bars: A, 50 µm; B–F, 100 µm.

Figure 27. The ‘jucundus group’. A–M, Anelosimus baeza. A, male palp mesal, from Baeza, Ecuador; B, same, ventral view; C, male palp ventral, from Colombia; D, epigynum, from Baeza, Ecuador; E–G, epigynum, from Las Caucheras, Ecuador. E, ventral view; F, internal epigynum, ventral; G, internal epigynum dorsal; H, male habitus, from Baeza; I, male habitus, from Las Cuacheras; J, female habitus, from Las Caucheras; K, same, profile; L, ectal view of male abdomen, from Baeza; M, ectal view of male abdomen, from Las Caucheras. N–Q, Anelosimus puravida. N, male palp mesal; O, same, ventral; P, epigynum; Q, internal epigynum dorsal.

Figure 29. Anelosimus baeza from Las Caucheras, male palp. A, dorsoapical view; B, mesal; C, submesal, apical view; D, ventral, note a conspicuous ectal tegular process (arrow); E, details of conductor, subconductor and embolus tip, ventral; F, palpal tibia, with three trichobothria (arrows). Scale bars: 100 µm.

Figure 31. Anelosimus baeza from Las Caucheras. A, epigynum; B, epiandrous gland spigots; C–F, female. C, abdomen ventral; D, abdomen surface; E, colular setae; F, posterior median and posterior lateral spinnerets. Scale bars: A,C,D, 100 µm; B,E, 50 µm; F, 10 µm.

Figure 33. Anelosimus puravida, male palp. A, dorsomesal view; B, apical, submesal; C, ventral; D, ectal, tip of palpus; E, apical, tip of palpus; F, details of embolus tip and conductor. Scale bars: 100 µm.

Figure 35. The ‘studiosus group’. A–F, Anelosimus tosum. A, male palp mesal; B, same ventral; C, epigynum; D, internal epigynum dorsal; E, female abdomen dorsal; F, same ectal. G–J, Anelosimus oritoyacu. G, male palp mesal; H, same ventral; I, epigynum; J, internal epigynum dorsal. K–Q, Anelosimus tungurahua. K, male palp mesal; L, same ventral; M, male habitus ectal; N, same, dorsal; O, female abdomen ectal; P, epigynum; Q, internal epigynum dorsal.

Figure 36. Anelosimus tosum, male palp. A, mesal view; B, submesal; C, ventral; D, ectal; E, apicoventral; F, details of embolus tip and conductor. Scale bars: 100 µm.

Figure 39. Anelosimus oritoyacu Ecuador, male palp. A, mesal view; B, submesal; C, ventral; D, ectal; E, details of distal sclerites, ventral; F, mesal view of distal sclerites. Scale bars: 100 µm.

Figure 42. Anelosimus tungurahua male palp. A, dorsal view; B, mesal; C, apical; D, ventral; E, ectal; F, details of embolus tip. Scale bars: A–E, 100 µm; F, 10 µm.

Figure 57. Characters III. A, Anelosimus nelsoni, note a finger-shaped lower branch of the theridiid tegular apophysis hook (arrow); B, Anelosimus nigrescens, note a blade-like lower branch of the theridiid tegular apophysis hook (arrow); C, Anelosimus ethicus, with a small, barely separate embolic division b (arrow); D, Anelosimus baeza male palp, ventral view, showing the sperm duct trajectory in the tegulum relative to position of sclerites; E, Anelosimus eximius, a schematic view of the sperm duct trajectory from ectal view (view as in G), F, Anelosimus eximius from above; G, Anelosimus baeza ectal view, showing switchbacks I and II.

Figure 63. A, Distribution of the Anelosimus lineage; B, distribution of A. domingo, A. dubiosus and A. jabaquara; C, distribution of A. oritoyacu, A. guacamayos, A. fraternus, A. pantanal and A. puravida.