RHIZOECINAE WILLIAMS

Hodgson, Chris, 2012, Comparison of the morphology of the adult males of the rhizoecine, phenacoccine and pseudococcine mealybugs (Hemiptera: Sternorrhyncha: Coccoidea), with the recognition of the family Rhizoecidae Williams 3291, Zootaxa 3291 (1), pp. 1-79 : 9-11

SUBFAMILY: RHIZOECINAE WILLIAMS

Rhizoecini Williams, 1969: 333

Rhizoecinae Williams : Koteja, 1974b: 45; Williams, 1985: 27; Tang, 1992: 42.

Introduction. Kozár and Konczné Benedicty (2005, 2007) recognised the following genera in the tribe Rhizoecini (here Rhizoecinae ): Benedictycoccina , Brevicoccus , Capitisetella , Coccidella , Geococcus , Hambletonrhizoecus (replacement name for Hambletonia Kozár & Foldi (2004)) , Kissrhizoecus , Leptorhizoecus , Marottarhizoecus , Pygmaeococcus , Pseudorhizoecus , Rhizoecus , Ripersiella and Williamsrhizoecus . However, earlier, Ferris (1953) and Williams (1998) had considered that Coccidella and Ripersiella were synonyms of Rhizoecus . Kozár and Konczné Benedicty (2007) present a key to all known genera based on adult female characters. According to Williams (1969), Danzig (1980) and Kozár and Konczné Benedicty (2005, 2007), adult females of Rhizoecinae are diagnosed by: antennae 5- or 6-segmented, their bases close together; eyes absent or hardly noticeable; claws without a denticle; anal ring with 2 rows of large elongated pores; anal lobules poorly developed, with a group of setae; presence of ostioles, multilocular and/or trilocular pores, tubular ducts and bi- and tritubular cerores, latter specific for subfamily; cerarii absent or C 18 only present; spines and spinules absent; hair-like setae present on both sides of body; living on plant roots. The character states that diagnose the adult males of this subfamily are given in the key above. The placement of Brevicoccus and Leptorhizoecus is here considered uncertain (discussed further below).

Subfamily diagnosis based on adult male morphology. Mounted material: macropterous, brachypterous or apterous. All morphs: small, total body length about 600–1025 µm; antennae fairly close together on anterior margin of head; body setae generally few but occasionally abundant, all hs (i.e. fleshy setae absent on body; all setae capitate on Capitisetella migrans ); loculate pores (lp) generally present and large, with 3–9 loculi; small simple pores (ssp) and minute sclerotised pores (msp) present or absent. Legs well developed. Head: rounded or approximately triangular in shape, apparently extending further posteriorly on dorsal surface than ventrally; without a neck. Dorsal epicranium at most lightly sclerotised throughout; median crest, midcranial ridge and postoccipital ridge absent; dorsal head setae (dhs) present between dorsal simple eyes (dse); lp present or absent dorsally. Ventral epicranium at most lightly sclerotised; a short ventral midcranial (vmcr) and lateral midcranial ridges (lmcr) present or absent; ventral head setae (vhs) present between antennae and anteriorly to preocular ridge (procr); lp present or absent ventrally; setae absent laterad to ventral simple eyes, but occasionally present posterior to ventral simple eyes (e.g. Ri. hibisci ) when here referred to as genal setae (gs). Genae (g) not differentiated from rest of head. Simple eyes (se) present or absent: generally with 2 pairs, ventral eyes (vse) fairly close together mid-ventrally, dorsal simple eyes (dse) approximately level with vse but generally much more lateral near margin; only 1 pair of simple eyes present in a few species, but simple eyes absent on others. Ocelli (o) absent. Ocular sclerite (ocs) not generally differentiated from rest of epicranium (possibly differentiated on Rh. dianthi and Rh. kazachstanus )); without reticulations around simple eyes. Preocular ridge (procr) present or absent; when present, restricted dorsally to a small sclerotisation laterad to each scape; ventrally, procr present as narrow ridges anterior to vse — occasionally appearing to fuse medially. Postocular, interocular and preoral ridges all absent. Cranial apophysis absent. Antennae: highly variable, usually 10-segmented (range 3–10) but reduced on some species (e.g., Ri. kondonis , C. migrans and Ps. proximus ); length very variable. Scape (scp) generally with 4 hair-like setae (hs). Pedicel (pdc) occasionally with a few concentric ridges on distal end and a variable number of fleshy setae (fs) and hs, possibly mainly on ventral surface, + 1 campaniform sensillum on dorsal surface (scape and pedicel barely differentiated on C. migrans and Ps. proximus ). Flagellar segments all highly variable in shape between species, some long and thin, others as wide as or wider than long; each generally with fs and hs; two subapical flagellar segments generally with an antennal bristle (ab). Apical segment often longest segment; not constricted apically; with fs (when recognisable), hs + ab; also with 1 or 2 sensilla basiconica (sb) on apex; with or without long flagellate setae which could be capitate setae but lacking capitate apices. Thorax. Prothorax: as wide as or wider than mesothorax and unusually long, sometimes showing slight signs of a constriction between pro- and mesothorax; pronotal ridge, pronotal sclerite and post-tergite absent; pronotum (prn) occasionally visible as a small, narrow transverse sclerotisation medially (e.g., on Rh. falcifer ); propleural setae (pl 1 s), median pronotal setae (mpns) and post-tergital setae (pts) generally present, often with lp and sometimes with ssp or msp; setal distribution much more random on apterous species. Antemesospiracular setae (am 2 s) and anteprosternal setae (astn 1 s) present or absent. Propleural ridge (plr 1) strongly sclerotised but short, not nearly reaching head. Sternum (stn 1) unsclerotised and without ridges or sternal apophyses on apterous species but transverse ridge of stn 1 and sternal apophyses generally present on brachypterous and macropterous species; median ridge absent; prosternal setae (stn 1 s) and lp present or absent.

Mesothorax: macropterous and brachypterous species: sclerites present but tending to be less well sclerotised on brachypterous species. Prescutum (prsc) oval to rather rectangular; sclerotised but not reticulated or nodulated; prescutal ridge (pscr) moderately well developed; prescutal suture (pscs) poorly defined or absent; with hs prescutal setae (prscs). Scutum (sct): median area sclerotised, without any membranous areas; scutal setae (scts) present; lateral margins not reticulated; sclerotised apodeme on anterior margin of scutum near prealare (pra) generally distinct (particularly obvious on Rh. falcifer ); prealar ridge (prar) well developed; triangular plate (tp) present although sometimes obscure. Scutellum (scl) rectangular, with a distinct scutellar ridge (sclr) on macropterous species, but ridge absent on brachypterous species; foramen absent; scutellar setae (scls) present; postnotal wing process (pnp) thin and extending laterally. Mesopostnotum (pn 2) and postnotal apophysis (pna) well developed; area bounded anteriorly by scutellum and laterally and posteriorly by mesopostnotum unsclerotised. Mesepisternum (eps 2) not reticulated; subepisternal ridge (ser) generally poorly defined. Postalare (pa) without reticulations; without postalare setae. Basisternum (stn 2) without a median ridge; bounded anteriorly by a narrow marginal ridge (mr) (particularly weak on Rh. dianthi ), and posteriorly by fairly strong precoxal ridges (pcr 2); with hs basisternal setae (stn 2 s); lateropleurite (lpl) quite broad and usually distinct, with or without an extension from marginal ridge along anterior margin; furca (f) well developed. Mesothoracic spiracles (sp 2) with poorly developed muscle plate; often with associated loculate pores (lp). Postmesospiracular setae (pm 2 s) generally present. Tegula (teg) large, with or without tegular setae (tegs).

Mesothorax: apterous species: all sclerites absent. Generally with 2 rows of hs (and often lp) across dorsal surface; ventrally with postmesospiracular setae (pm 2 s) and loculate pores. Furca (f) moderately well developed, with divergent arms. Mesopleural ridge (pl 2 r) well developed but short. Spiracles as on winged morphs.

Metathorax: macropterous and brachypterous species: with distinct groups of hs metatergal setae (mts); metapostnotum (pn 3) present or absent. Dorsal part of metapleural ridge absent; ventral part of metapleural ridge well developed (less so on apterous species); metepisternum (eps 3) not sclerotised and without postmetaspiracular setae; precoxal ridge absent; metapleural ridge (plr 3) with or without an additional narrow sclerotised ridge or fold extending ventrally from near coxal articulation. Metepimeron (epm 3) present or absent, without setae. Antemetaspiracular setae absent. Metathoracic spiracle (sp 3) as for mesothoracic spiracle; often with associated loculate pores. Dorsospiracular setae (dss) generally present. Metasternum (stn 3) lightly sclerotised, with hs anterior metasternal (amss) and posterior metasternal setae (pmss).

Metathorax: apterous species: basically rather similar but dorsal setae (metatergal (mts) and dorsospiracular setae (dss)) generally forming a complete row or band of setae; ventrally, postmetaspiracular setae (eps 3 s) sometimes present. Metepimeron (epm 3) absent.

Wings: when present, hyaline; macropterous species with wings about as long or longer than body; brachypterous species with much shorter wings; with distinct microtrichia; alar lobe (al) very small or absent; each wing with hs alar setae (als) + circular sensoria (sens) close to base of wing. Hamulohalteres absent.

Legs: metathoracic legs often longest. Trochanter (tr) with 2 or 3 roundly oval sensoria, and with or without a strong, Y-shaped sclerotised ridge for articulation with femur; long trochanter seta undifferentiated. Tibia (ti) with hs setae, becoming spur-like distally; number of tibial spurs (tibs) on protibia sometimes less than on other tibia. Tarsi (ta) 1 or 2 segmented; when 2 segmented, proximal segment very short and ring-like; tarsi with tarsal spurs not differentiated; tarsal campaniform pore present (possibly absent on K. hungaricus ); tarsal digitules (tdgt) long and generally setose, but sometimes with minutely capitate apices. Claws (c) very long and thin, almost straight, generally without a denticle ( Ri. puhiensis with a hint of one); claw digitules (cdt) setose and finely pointed, sometimes very short.

Abdomen: segments I–VII: tergites (at) and sternites (as) often lightly sclerotised, particularly on alate species; pleurites (apl) on VI and (particularly) VII occasionally lightly sclerotised; without obvious oval membranous areas in inter-segmental membranes (as present on some less "primitive" neococcoids). Caudal extension (ce) on segment VII generally absent but occasionally present ( Ri. hibisci ). Loculate pores (lp), simple pores (ssp) and minute sclerotised pores (msp) present or absent; dorsal setae (ads) often in lines across each segment, even apparently forming a complete ring. Ostioles absent. Segment VIII generally with tergite (at) and sternite (as) distinctly sclerotised; tergite generally with hs dorsal abdominal setae (ads) and loculate pores (lp) medially; sternite often without setae but sometimes with 1 pair of shorter setae but no lp; caudal extension (ce) on segment VIII rounded, with 1 short hs ventral pleural seta (vps) on each side plus 1–3 long robust setae in position of glandular pouches (absent on Ri. malchae , C. migrans and Ps. proximus ). Glandular pouches absent. Genital segment: penial sheath (ps) rather large and triangular; broad, almost as wide as abdominal segment VIII ventrally; rather variable in shape but narrowing posteriorly to a pointed upturned apex. Dorsal surface with a large anus (a) anteriorly. Dorsal penial sheath setae variable, often with 2 or 3 pairs of longish setae posterior to anus but Ri. malchae and Ps. proximus with many more. Ventrally, with a median slit-like opening through which aedeagus (aed) emerges; borders of slit may be well or lightly sclerotised; margins of ps with 1 or 2 pairs of setae, generally short. Aedeagus C-shaped, with a strong basal rod (bra); apex possibly variable. Apex of penial sheath with small sensilla (psp).

Descriptions of adult males of Rhizoecinae : the generic placement of these 15 species is that in Kozár and Konczné Benedicty (2007).