Walterianella bucki, BECHYNE, Bechyne

Description of Immatures

Egg ( Fig. 1C View Fig ). Pale orange. Micropyle apically, deep; chorion reticulate (see Fig. 1C View Fig ). Eggs are laid in star­shaped clusters with long axes perpendicular to the substrate.

Larva. White, (in alcohol, blackened).

First Instar Larva. Length 2.0–2.2 mm.

Habitus. Body eruciform ( Fig. 1A View Fig ), slightly dorso­ventrally flattened, weakly arched in preserved specimens, with prominent tubercles bearing club­like setae ( Fig. 1B View Fig ) (all setae except as noted below club­like); head hypognathous, well sclerotized, brown, antenna, maxillae and labium partially membranous; legs moderately pigmented and sclerotized.

Head rounded, moderately pigmented and well sclerotized; frontal arms V­shaped, slightly arched, epicranial stem short; endocarina distinct, extending from base of clypeus to epicranial stem. Frons bearing 3 pairs of simple setae and one pair of placoid sensilla; each epicranial half bearing 4 setae, 1 placoid sensillum at antennal base, and 5 microsetae dorsally. Stemma absent. Antennifer membranous, longer than 1st segment. Antenna 2 segmented ( Fig. 1E View Fig ), slightly sclerotized, 1st segment telescoped as in Figure 1A View Fig , bearing 1 coniform membranous sensillum, 6 pedunculate stout setae near apex, and 2 placoid sensilla at border of sclerotized band; distal segment membranous, conical, slightly sclerotized in a basal band. Clypeus transverse, narrow, bearing 2 pairs placoid sensilla and 2 microsetae. Labrum transverse, slightly sclerotized, sclerotized and melanized portion apically emarginate, bearing 2 pairs stout setae and 1 pair placoid sensilla.

Prothorax slightly narrower than other segments, integument coarsely reticulate; pronotum flattened, shield­like, bearing 8 pairs club­like setae each borne on a minute tubercle; small epipleural tubercle bearing 1 club­like seta, just anterior to thoracic spiracle, and small prehypopleural tubercle anterior to coxa also bearing 1 club­like seta; sternum bearing small triangular sclerite at midline bordered by 1 pair thickened setae, egg bursters lacking. Thoracic spiracle annuliform, relatively large. Meso and metanotum each bearing 2 pairs setae, 1 pair median prescutal borne on small tubercle and posterior parascutal pair each borne on small tubercle at base of epipleural tubercle; pleuron bearing large lateral epipleural tubercle bearing 2 pairs setae, 1 small pre­hypopleural tubercle anterior to coxae each bearing 1 seta; ventrum bearing 2 pairs setae, segments devided by transverse groove forming two plicae, each plica bearing 1 pair setae. Legs ( Fig. 1D View Fig ): 5­segmented, all pairs approximately equal in size; coxae bearing 8 setae, 4 small simple setae and 4 long club­like; trochanters triangular bearing 2 minute setae dorsally, 3 longer setae ventrally, and 5 placoid sensilla; femora subquadrate bearing 3 minute setae dorsally and 3 longer setae on inner margin, 2 stout; tibiae sub­conical, bearing 4 stout setae; tarsungulus bearing 1 simple seta on inner margin, paronychial appendix absent.

Abdominal segments I–VII bearing 2 pairs dorsal setae, 1 pair median­prescutal and 1 pair parascutal, each borne on small tubercle; pleuron bearing large foliform peltate epipleural tubercles each bearing 1 seta, 1 small post­hypopleural tubercle each bearing 1 seta, just posterior and ventral to spiracle; ventrum bearing 4 pairs setae, 1 median anterior pair simple setae, borne on minute tubercles, 2 pairs lateral posterior borne on small tubercle, exterior usually simple, interior always club­like, ( Fig. 1B View Fig ) 1 pair posterior intermediate simple setae borne on minute tubercle. Seventh segment with epipleural tubercle larger. Eighth abdominal segment bearing extremely large bi­apical tubercles, bearing long stout setae, hypopleural tubercle slightly larger than other segments, spiracle on anterior side of tubercle, ventrum as in segments I–VII. Ninth segment smaller than eighth, bearing 4 pairs setae dorsal to tenth segment, 2 pairs oriented posteriorly, and 2 pairs simple oriented ventrally, ventrum bearing 2 pairs lateral simple setae. Segment X asetose, forming anal pseudopod.

Mature Larva. Length 4.0–5.5 mm.

Habitus. Body eruciform ( Figs. 2A View Fig and 3A View Fig ), slightly dorso­ventrally flattened, arched in preserved specimens, with prominent tubercles bearing club­like setae (all setae except as noted below club­like); head hypognathous, well sclerotized, dark brown, antennae, maxillae and labium slightly sclerotized; legs moderately pigmented and sclerotized.

Head rounded ( Fig. 2B View Fig ), moderately pigmented and well sclerotized; frontal arms Vshaped, slightly arched, epicranial stem short; endocarina distinct, extending from base of clypeus to epicranial stem. Frons ( Figs. 2B View Fig , 5B View Fig ) bearing 3 pairs of stout setae, one pair of microsetae and one pair of placoid sensilla; each epicranial half bearing 4 setae and 1 placoid sensillum at antennal base and 5 microsetae dorsally. Stemma absent. Antennae, clypeus and labrum as in 1st instar, but see Figures 2B View Fig and 4B View Fig . Epipharynx with dense area of microtrichia in median anterior area ( Fig. 4C View Fig ), anterior margin bearing 6 pairs stout pedunculate setae, 2 lateral­most pairs foliate, and 2 groups of campaniform sensilla near anterior margin; lateral areas of epipharyx bearing 2 bands of minute, irregular, microtrichia. Mandibles symmetrical ( Fig. 4D, F View Fig ), palmate, 5 toothed; external face bearing 2 setae and 2 sensory pores; penicillus formed by thickened setae. Maxillae ( Fig. 5A View Fig ): cardo transverse, bearing 1 seta laterally, with one sclerotized melanized area; stipes elongate, bearing one long seta on melanized area and one lateral on membranous area; one sensilla at border of melanized area; mala palpiform, 3­segmented, basal segment transverse, bearing 6 pedunculate setae; 2nd segment elongate; distal segment short; one pedunculate seta near intenal margin; maxillary palpi 3­segmented, 2 basal segments membranous at apex; basal segment bearing basally one minute seta and interio­apically one campaniform sensillum, 2nd segment bearing one campaniform sensillum medially and one small seta laterally, apical segment bearing one digitiform sensillum laterally and one short seta laterointerioraly. Dorsal area of maxillae ( Fig. 5C View Fig ) bearing 14 stout pedunculate setae of varied size distributed near margin; microtrichiae on apex. Labium ( Figs. 4A View Fig , 5A View Fig ): prementum membranous with a transverse sclerotized area bearing 2 pairs setae, one long and one minute and basal; postmentum membranous bearing 2 pairs well devolped setae and 2 campaniform sensillae; labial palpi 2­segmented; basal segment with ventro­medial sensory pore; distal segment with 1 placoid sensillum ventrally and 3 small membranous cone­like sensilla apically; ligula narrow, each half bearing 2 campaniform sensilla and 3 short stout setae, 1 minute. Hypopharyx ( Fig. 4E View Fig ) bearing apically, on each side, 2 placoid sensilla and 3 stout setae, one longer; above clothed with microtrichia (not shown).

Prothorax slightly narrower than other segments, integument coarsely reticulate; pronotum ( Fig. 2D View Fig ) flattened, shield­like, bearing 8 pairs club­like setae, each borne on a minute tubercle, in two rows; small epipleural tubercle bearing 1 seta, just anterior to thoracic spiracles, and small prehypopleural tubercle anterior to coxae also bearing 1 seta; sternum bearing small triangular sclerite at midline with 1 pair simple setae almost at midline. Thoracic spiracle annuliform, relatively large. Meso and metanotum each bearing 3 pairs setae, 1 pair median prescutal borne on small tubercle, 1 median scutal borne on small tubercle and posterior parascutal pair each borne on small tubercle at base of epipleural tubercle; pleuron bearing large lateral epipleural tubercle bearing 2 pairs setae, 1 small pre­hypopleural tubercle anterior to coxae each bearing 1 seta, ventrum bearing 1 pair simple setae each midway between leg and midline. Legs ( Fig. 2C View Fig ) as in first instar.

Abdominal segments I–VII bearing 3 pairs dorsal setae, 1 pair median­prescutal, 1 median scutal pair borne on small tubercle and 1 pair parascutal borne on prominent tubercle; pleuron bearing large foliform epipleural tubercles each bearing 1 pair setae, 1 small post­hypopleural tubercle each bearing 2 setae, just posterior and ventral to spiracle; ventrum divided by transverse groove forming two plicae, bearing 5 pairs thickened but not club­like setae, 1 median anterior pair setae borne on minute tubercles on first plica, posterior plica with 4 pairs lateral setae each pair borne on small tubercle ( Fig. 3A View Fig ). Seventh segment with epipleural tubercle larger, Eighth abdominal segment bearing only 1 pair pre­scutal setae, bearing extremely large bi­apical epipleural tubercles, bearing long simple setae, hypopleural tubercle slightly larger than other segments, spiracle on anterior side of tubercle, ventrum as in segments I–VII. Ninth segment smaller than eighth ( Fig. 3B View Fig ), bearing 4 pairs setae dorsal to tenth segment, 2 pairs oriented posteriorly, and 2 pairs simple oriented ventrally, ventrum bearing 1 pair medial and 2 pairs lateral, thickened setae. Segment X small asetose, forming anal pseudopod ( Fig. 3B–C View Fig ).

Material Examined. All material from Maquine´, FEPAGRO Experiment Sta ., Rio Grande do Sul State, 1998, C. N. Duckett leg. 6 eggs laid 15 Feb.; 6 eggs, 5 March. Larvae: 5, 1st instar, 25 Feb.; 4, 2nd instar, 13 March; 2, probably 3rd instar, 18 March; 1 3rd instar, 24 March. Deposited in Museu de Zoologia da Universidade de São Paulo ( MZSP) and Adults, 12 ex. Feb. and March 1998, 10 deposited in Fundação Zoobotânica do Rio Grande do Sul ( MCNZ), 2 deposited at MZSP .

Life History

Walterianella bucki is found on Buddleja sp. , which is a highly pelose species of weedy plant that inhabits moist disturbed habitats. Adults are found under leaves or bracts during the day and actively feed and copulate on both leaf surfaces at night. Walterianella bucki is often found in conjunction with Capriaita clarissa Bechyne´, a much smaller species whose elytral patterning is almost identical to W. bucki . Both species are nocturnal and found easily only at night. After death pinned or alcohol­preserved W. bucki may be stramineous or grey in color or black in low concentrations of alcohol. In life, the elytra are a pale straw color that appears silvery with a flashlight; the terga and ventrum are a pale orange color.

Walterianella bucki larvae and pupae were never observed in nature. In culture, eggs were laid in tissue paper near plant roots or on plant roots and larvae only fed on leaves which were obviously moribund and sandwiched together—feeding between the leaf surfaces, or on root surfaces. Larvae were very active and highly motile. Because of these facts and the lack of observed larvae on plants, where many adult W. bucki were continuously present, larvae are assumed to inhabit the leaf litter and probably eat decomposing leaves (at least for part of their diet) and possibly root hairs or small surface roots.

Eggs hatched after 10 days at room temperature under late Summer conditions in Maquine´. Larvae developed slowly, which is consistent with the known life histories of other Oedionychine flea beetles. Alagoasa bicolor in Puerto Rico averages 50 days from egg to adult (Virkki and Zambrana 1980, 1983), Alagoasa januaria in Southern Brazil takes a similar length of time (Virkki 1972). Approximately 22 days after hatching a 3rd instar larva was obtained; larvae were sacrificed after 30 days because of high mortality and no visible evidence of prepupal behavior which should have been apparent at this time; postmortem examination indicated an incipient fungal infection in mature larvae. It must be noted that the best food and conditions for development were almost certainly not available for these larvae.