Pelionella osakaensis, Tanaka, Hirotaka, 2018

Tanaka, Hirotaka, 2018, First records of the genus Pelionella Kaydan, 2015 in East Asia, with description of a new species (Hemiptera, Coccomorpha, Pseudococcidae), ZooKeys 738, pp. 47-58 : 50-53

Pelionella osakaensis sp. n. Figure 2

Holotype.

Adult ♀. Japan, Osaka-pref., Sennan City, Kansai International Airport, 12.X.2014, host plant: Artemisia indica var. maximowiczii , coll. K. Fujimoto. (NSMT-I-Ho 00081).

Diagnosis.

Eighteen pairs of cerarii present on body margin. Several slightly elevated dorsal cerarii also present on dorsal surface. Clusters of multilocular pores with double rings present on dorsum; each cluster contains 1-2 multilocular pores with double rings, 0-1 small oral-collar tubular ducts, 0-2 large oral-collar tubular ducts, and 0-3 minute discoidal pores. Multilocular pores with double rings and clusters of multilocular disc pores with single ring and oral-collar tubular ducts absent on venter. Circulus oval, present on posterior part of third abdominal segment of venter. Translucent pores absent on hind legs.

Description.

Slide-mounted specimen.Adult female. Body elongate oval, 1.7 mm long, 0.9 mm wide. Eyes submarginal, each 30-32 μm in diameter. Antenna 9-segmented, 363-387 μm long; apical segment 53-57 μm long, 20-25 μm wide; with two apical setae each 30-38 μm long, and three fleshy setae each 20-30 μm long. Labium 103 μm long, 68 μm wide. Circulus oval, approx. 74 μm wide, situated on posterior part of third abdominal segment. Legs well developed; posterior legs: coxa 82-85 μm long; trochanter + femur 248-250 μm long; tibia + tarsus 275-278 μm long; claw 30-34 μm long. Translucent pores absent. Ratio of lengths of hind tibia + tarsus to trochanter + femur 1.1:1; ratio of lengths of tibia to tarsus 1.4-1.5:1; ratio of length of trochanter + femur to greatest width of femur 3.0:1. Tarsal digitules hair-like, each 20-31μm long. Claw digitules knobbed, each 28 μm long. Claw with well-developed denticle on plantar surface. Anterior ostioles with a total for both lips of 26 to 30 trilocular pores and 2-3 setae; posterior ostioles with a total for both lips of 33-36 trilocular pores and 5-6 setae. Anal ring 85 μm wide, bearing 6 setae, each seta 103-125 μm long.

Dorsum. Cerarii on margins slightly prominent but with no sclerotization, numbering 18 pairs; anal lobe cerarii each with 2-3 slender enlarged setae, each 11-21 μm long, and 2-3 spine-like auxiliary setae; other cerarii on margins each with 2-3 slender enlarged setae and several trilocular pores. Several dorsal cerarii present on dorsal surfaces as shown in Figure 2, each cerarii with 1-2 relatively small enlarged setae, no auxiliary setae and several triolocular pores; each slightly prominent but with no sclerotization. Setae spine-like, each 5-15 μm long; larger setae each with 1-3 trilocular pores near base, sometimes forming dorsal cerarii. Multilocular pores with double rings, each 5.5-6.2 μm in diameter, in each cluster present singly or in pairs together with 0-1 small oral-collar tubular ducts, 1.8-2.0 μm wide, plus 0-2 large oral-collar tubular ducts, each 2.5-2.8 μm wide, and 0-3 minute discoidal pores, each 1.2-1.8 μm in diameter. Clusters few on head and thorax, and present on abdominal segments as follows: I 4, II 4, III 11, IV 11, V 13, VI 2, VII 3, VIII+IX 0. Trilocular pores, each 3.2-3.8 μm in diameter, scattered throughout. Several small oral-collar ducts, each 1.8-2.0 μm wide, and minute discoidal pores, each 1.2-1.8 μm in diameter, sometimes present outside the clusters.

Venter. Setae of two types: (i) hair-like setae, each 14-81 μm long, longest present on medial area of posterior abdominal segments; and (ii) spine-like setae, each 5-10 μm long, present in submarginal areas. Apical setae of anal lobes each 162-169 μm long. Multilocular disc pores, each 5.5-6.5 μm in diameter, present in bands on abdominal segments as follows: IV 4, V 0, VI 28, VII 34, VIII + IX 29. Quinquelocular pores, each 3.5-4.5 μm in diameter, scattered medially on head, thorax, and first four abdominal segments. Trilocular pores, each 2.8-3.2 μm in diameter, scattered throughout. Minute discoidal pores, each 1.0-1.2 μm in diameter, few in number. Oral-collar tubular ducts of 1size, each 1.9-2.1 μm wide, mostly present in bands across posterior abdominal segments and on medial areas of thoracic segments; a few ducts present in submarginal areas.

Etymology.

The species is named after the prefecture in Japan where it was collected.

Discussion.

Pelionella osakaensis sp. n. is quite similar to P. grassiana (Goux, 1989) and P. proeminens (Goux, 1990) in having clusters containing one or two multilocular pores with double rings on dorsum and more than 16 pairs of cerarii. However, P. osakaensis differs from the latter species in having a circulus on the posterior part of the third abdominal segment, several slight elevated dorsal cerarii, and in lacking translucent pores on hind legs. Although the presence or absence of a circulus can be variable within a mealybug spe cies, it may be a useful, readily observable diagnostic character for P. osakaensis given the current status of classification of Pelionella species. Pelionella osakaensis is also similar to P. stellarocheae (Goux, 1990) in lacking translucent pores on hind legs and in having smaller number of multilocular pores with double rings in each cluster on dorsum; however, it clearly differs from P. stellarocheae in having 18 pairs of cerarii plus dorsal cerarii. The presence of dorsal cerarii is one of the important features of P. osakaensis , although it may appear to conflict with the generic definition of Pelionella proposed by Kaydan (2015). Here the importance of the presence of multilocular pores with double rings in the clusters is emphasized, so the new species is considered to belong to the genus Pelionella . Further research into the generic definition of the genus Pelionella is still much needed.

Pelionella osakaensis has only been collected from the site of Kansai International Airport, one of the largest airports in Japan, so it is possible that it is not endemic. A more detailed distributional study of the species and the current population level and distribution of the species at the airport may be important in relation to plant-quarantine measures.

Key to species of the genus Pelionella based on adult female morphology (adopted and partially modified from Kaydan 2015)