Neochavesia

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 : 58-60

Neochavesia nr. trinidadensis Beardsley

( Fig. 21 ).

Material examined. Trinidad [as British West Indies], San Rafael, 31.v.1935, in clay under cocoa tree ( Theobroma sp. , Sterculiaceae ), N.A. Weber ( USNM): 1/ 1♂ in good condition (labelled Neochavesia ? trinidadensis Beardsley ).

Mounted material: apterous. Very small, total body length about 0.84 mm, greatest width 425 µm; antennae 2 segmented, short, with a few minute setose setae except on apex which has longer setae and antennal bristles; setae on head, thorax and 1st abdominal segment all minute (about 1 µm long); fleshy setae (fs) absent; loculate (lp) and simple pores absent. Without either ocelli or simple eyes; legs with mainly minute setae; tarsi 1 segmented, with minute tarsal digitules; trochanter with 2 pairs of campaniform pores; claw short and stout.

Head: rounded anteriorly; posterior margin not determined. Dorsal epicranium apparently unsclerotised and without a median crest (mc), midcranial ridge (dmcr), preocular ridges or postoccipital ridge (por); with a few minute dorsal head setae (dhs), each perhaps 1–2 µm long. Genae (g), simple eyes and ocelli absent. Ocular sclerite (ocs) not differentiated. Ventral epicranium unsclerotised, without any sign of ventral midcranial ridge (vmcr) or lateral arms of midcranial ridge (lmcr); with a few minute ventral head setae (vhs). Postocular (pocr), interocular (ior) and preoral ridges (pror) all absent. Cranial apophysis (ca) absent. Mouthparts absent.

Antennae: 2 segmented; length about 190 µm long (ratio of total body length to antennal length 1:0.23). Scape (scp): 43 µm long, 60 µm wide, with 3 or 4 minute hs; quite wide apart near anterior margin of head. Segment II: length 153 µm, width 50 µm, tapering slightly towards apex; with perhaps 16 minute setae mainly towards distal end; no campaniform pore found. Antennal apex with 3 antennal bristles (each perhaps 34–46 µm long), about 5 stiff setae (each about 25–33 µm long) and 2 very short (fleshy?) setae on apex (each 5 µm long).

Thorax. Division into pro-, meso- and metathorax unclear, apart from position of legs. Dorsal derm with a few minute setae, exact distribution uncertain; ventrally with a very few similar setae. Mesothoracic (sp 2) and metathoracic (sp 3) spiracles: width of peritremes about 21–26 µm. No basisternal furca detected. Pleural ridges all developed but short. Metasternum (stn 3) unsclerotised; presence of metasternal setae unknown.

Wings and hamulohalteres (h) absent.

Legs: metathoracic legs possibly longest. Coxae (cx): I 88; II 85–87; III 79–85 µm long; coxa III with 5 or 6 hs, all minute; long setae on each coxa not differentiated. Trochanter (tr) + femur (fm): I 115–120; II 122–125; III 123–130 µm long; trochanter III with about 4 hs, all minute; each trochanter with 2 roundly oval sensoria in a line parallel to trochanterofemur articulation; without strong, Y-shaped sclerotised ridges; long trochanter seta not differentiated; femur III with 7 or 8 minute hs. Tibia (ti): I 64–66; II 68–70; III 78–80 µm long; tibia III with a total of 10 minute setae; all tibiae with 2 setose apical spurs (tibs); length of longest 8–10 µm. Tarsi (ta) 1 segmented; length (µm): I 43–45; II 43–45; III 45–48 (ratio of length of tibia III to length of tarsus III 1:0.68); tarsus III with 2 minute setae + 3 larger setae, those ventrally more spur-like; tarsal spurs not differentiated; tarsal campaniform pore present; tarsal digitules (tdgt) very short and setose. Claws (c) short and rather broad, without a denticle; length: III 21 µm; claw digitules (cdt) very short and setose, arising from centre of claw.

Abdomen: segment I not apparently differentiated dorsally; segment II wide, but narrowing so that segments III–VIII are all much narrower, perhaps 1/2–1/4 width of thorax: tergites (at), sternites (as) and pleurites (apl) unsclerotised. Caudal extensions (ce) of segment VII absent; ce on VIII large and appearing similar to anal lobes. Loculate pores (lp) absent; setae in a single band around each segment, not apparently separated into dorsal, pleural and ventral abdominal setae; fewest and shortest on segment III, becoming longer and more abundant posteriorly; approximate number of setae per segment: III 26, IV 31; V 33, VI 42 and VII 36 (length about 33–37 µm) and VIII abundant, each up to 75 µm long. Ostioles absent. Segment VIII without a pair of glandular pouches, but lobe with numerous long setose setae.

Genital segment: anus not detected. Penial sheath (ps) represented by a large oval sclerotised structure about 130 µm long, 40–45 µm wide, extending under segment VIII and protruding slightly between posterior lobes; posteriorly drawn out into a sclerotised finger-like structure which appears to have a ring of spines near apex. Penial sheath apparently without setae and no sensilla detected on posterior apex. Ventrally, aedeagus long and spine-like, about 140 µm long; on only available specimen, this extends antero-ventrally but this may be due to mounting; basally aedeagus with a strongly sclerotised area (probably internal genital aperture (iga) or basal rod (bra).

Comment. This specimen, although labelled N.? trinidadensis , is unlikely to belong to this species. Williams (2004a) found that both the males and females of N. caldasiae and N. lapollai had 5-segmented antennae. He also pointed out that the adult female of N. trinidadensis had 5-segmented antennae — but the male described above has only 2-segmented antennae. Although the large lobes on abdominal segment VIII are very similar to those on N. caldasiae and N. lapollai , the reduction in the number of antennal segments is more suggestive of Eumyrmococcus and the very long aedeagus (apparently longer than the penial sheath) is also seen in E. smithii Silvestri. Although it is considered here that this male probably does belong to an undescribed species of Neochavesia , it is clear that it falls somewhere between the known males of these two genera. The adult males of Eumyrmococcus and Neochavesia are rather similar. All are neotenic, apterous and have a swollen head and thorax, which then narrows more or less abruptly to form a long narrow abdomen. Williams (1998) speculated that the narrow abdomen is to assist transport by the host ants. For separation of the adult males of these 3 species, see key.

Figures

FIGURE 21. Neochavsia nr. trinidadensis (Beardsley). Adult male. Where H = apex of antenna; K = distal end of posterior leg, and N = oblique ventral view of penial sheath. For other labels, see under Materials and methods: conventions.