Research Article |
Corresponding author: Hirotaka Tanaka ( coccoidea@gmail.com ) Academic editor: Roger Blackman
© 2016 Hirotaka Tanaka.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Tanaka H (2016) A new genus and species of Rhizoecidae (Hemiptera, Sternorryncha, Coccomorpha) associated with Acropyga yaeyamensis (Hymenoptera, Formicidae, Formicinae). ZooKeys 616: 115-124. https://doi.org/10.3897/zookeys.616.9442
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Ishigakicoccus gen. n. shimadai sp. n. is described based on the adult female morphology. This new species was found in the nest of a rare Japanese ant, Acropyga yaeyamensis Terayama & Hashimoto, 1996, in Ishigaki Is., Japan. It resembles Capitisetella migrans (Green, 1933) and Pseudorhizoecus proximus Green, 1933. However, the new species differs from those two species in having small multilocular pores, large 3-5 locular pores on the medial area of ventral abdomen, and two different-sized body setae. This new species is also the first record of a potential trophobiont of A. yaeyamensis. A key to Japanese species of Rhizoecidae is also provided.
Ant trophobiont, ground mealybug, new genus, root mealybug, taxonomy
Rhizoecidae is a family of Coccomorpha (Hemiptera: Sternorryncha) which members mostly live underground, feeding on plant rootlets (
Some genera and species placed in Rhizoecidae, especially those classified in the tribe Xenococcini, show very close trophobiotic relationships with ants that belong to the genus Acropyga (Hymenoptera: Formicidae: Formicinae) (
Recently, the author had an opportunity to examine several interesting mealybug specimens that were collected from the nest of A. yaeyamensis which showed a close association with the ant (Figure
This paper describes and illustrates this mealybug as a new genus and species on the basis of adult female morphology. A key to Japanese species of Rhizoecidae is also given.
Specimens of the root mealybug species used in this study were originally collected by a collaborator of this study, Mr. Taku Shimada, on 16 February 2015, from a nest of A. yaeyamensis Terayama & Hashimoto, 1996, in Mt. Omoto, Ishigaki Is., Japan. The mounting method used for these specimens followed that described by
Rhizoecus Künckel d’Herculais, 1878
Same as for the family, except the characters related to Xenococcini (adopted and modified from
Ripersiella Tinsley, 1899 in
Same as the family, except the characters related to Xenococcini, Geococcina and Rhizoecina. Most of the species have bitubular pores, and 5–6 segmented antennae. In some monotypic genera, included tentatively, the anal ring and/or the antennae are reduced (adopted and modified from
Ishigakicoccus shimadai sp. n., here designated.
Body elongate oval, slightly pyriform. Eye spot absent. Antennae 5 segmented. Legs well-developed. Two types of body setae present on both dorsal and ventral body surface. Small sized multilocular pores present, each with 5–6 loculi. Tritubular and bitubular pores absent. Oral collar tubular ducts absent. Ostioles absent. Anal ring irregular oval; anal pores and anal ring setae absent. Large 3–5 locular pore without central hub, present on medial area of ventral abdomen. A circulus present.
Named after the island (Ishigaki) where the type species was collected first. The suffix coccus is commonly used in naming Coccomorpha genera. Gender: masculine.
Holotype, adult female. Japan, Okinawa-pref., Ishigaki Is., Mt. Omoto, 16.II.2015. coll. T. Shimada 1♀ (
Body elongate oval, slightly pyriform, 721–895 µm long, 379–632 µm wide. Eye spot absent. Antennae 5 segmented, 1st : 18.4–29.5 µm long, 2nd : 13.7–18.4 µm long, 3rd : 15.8–26.3 µm long, 4th : 17.1–22.1 µm long and 5th : 36.8–41.3 µm long. The fifth segment with three fleshy setae. Anterior spiracles each 20.8–28.7 µm wide across atrium; posterior spiracles each 16.8–29.7 µm wide across atrium. Legs well developed, length of posterior pair: coxa 45.8–55.2 µm long, trochanter + femur 123–133 µm long, tibia + tarsus 112–122 µm long, claw 33.4–39.4 µm long. Ratio of lengths of tibia + tarsus to trochanter + femur 1.05–1.11. Claw digitules setose, each 3.2–6.1 µm long.
Dorsum: Two types of body setae present. Type I: relatively well developed setae, 19.7–58.9 µm long, some setae with a bent or rarely with a knobbed apex. Type II: relatively slender setose setae, 11.0–32.8 µm long, each with a pointed apex. Both types of setae distributed in transverse segmental rows. Multilocular pores each about 2.9–3.7 µm in diameter, each with 5–6 loculi, present on head and thorax, but rarely present on abdomen (Figure
Venter: Labium appearing 2 segmented, 100–107 µm long, 48.4–62.0 µm wide. Two types of body setae present: type I, relatively well developed setae, 18.4–65.3 µm long, some setae with a bent and a rarely knobbed apex.; type II, relatively slender setose setae, 10.5–37.4 µm long, each with a pointed apex. Both setae distributed in transverse segmental bands. Multilocular pores each about 2.9–3.7 µm in diameter, each with 5–6 loculi, frequently present and evenly distributed on all areas of venter. 3–5 locular pores, each 5.8–7.9 µm in diameter, without central hub, present on medial area of abdominal segments III–VI in transverse rows. A circulus, 10.5–18.4 µm long and 21.0–33.2µm wide present on medial anterior border of abdominal segment II. Tritubular and bitubular pores absent. Oral collar tubular ducts absent.
Named after the collector of the type specimens.
Unknown.
1 | Ostioles present | 2 |
– | Ostioles absent | 9 |
2 | Anal lobes well-developed, with stout spine-like setae | 3 (Genus Geococcus) |
– | Anal lobes not well-developed, without stout spine-like setae | 4 |
3 | Stout, spine-like setae on dorsum present. Multilocular pores with 7–10 loculi, present on ventral surface (around vulva) | Geococcus oryzae (Kuwana, 1907) |
– | Stout, spine-like setae on dorsum absent. Multilocur pores with 6 loculi present on all segments of venter and most segments of dorsum | G. citrinus Kuwana, 1923 |
4 | Tritubular pores present. Bitubular pores absent | 5 (Genus Rhizoecus) |
– | Tritubular duct absent. Bitubular pores present | 6 (Genus Ripersiella) |
5 | Multilocular pores absent on venter | Rhizoecus cacticans (Hambleton, 1946) |
– | Multilocular pore present on ventral surface of posterior abdominal segments | Rh. advenoides Takagi & Kawai, 1971 |
6 | Multilocular pores absent on venter | Ripersiella sasae (Takagi & Kawai, 1971) |
– | Multilocular pores present at least on ventral surface of posterior abdominal segments | 7 |
7 | Multilocular pores present on venter and dorsum (at least on medial part of two segments of dorsum) | Ri. hibisci (Kawai & Takagi, 1971) |
– | Multilocular pores pores only on venter (often some on dorsum, but only on medial part of segment VII) | 8 |
8 | With two circuli | Ri. kondonis (Kuwana, 1923) |
– | With one circulus | Ri. theae (Kawai & Takagi, 1971) |
9 | Disc pores present on venter and dorsum. Antennae 5 segmented | Ishigakicoccus gen. n. shimadai sp. n. |
– | Disc pores absent. Antennae with 2 to 4 segments | 10 |
10 | Antennae 4 segmented | Xenococcus kinomurai (Williams & Terayama, 2000) |
– | Antennae 2 segmented | 11 (Genus Eumyrmococcus) |
11 | Circulus absent. Body with flagellate setae only, sensory setae absent on body surface | Eumyrmococcus smithii Silvestri, 1926 |
– | A small circulus present on abdominal segment III. Sensory setae present on body surface | E. nipponensis Terayama, 1986 |
The genus and species described in this paper slightly resembles two other species of the monotypic genera of Rhizoecidae, Capitisetella migrans (Green, 1933) and Pseudorhizoecus proximus Green, 1933, in lacking ostioles and tritubular and/or bitubular pores, and having a pyriform to round body shape. However, the former is clearly distinguishable from those two species by having small multilocular pores on both surfaces of the body, 3–5 large locular pores on the medial area of the ventral abdomen, and two different-sized body setae. These morphological differences are here considered as good for the establishment of a new genus. Based on some morphological similarity, the genus and species is tentatively placed in the subtribe Ripersiellina Kozár 2007 of the tribe Rhizoecini Williams, 1969, in which C. migrans and P. proximus are also placed (
In east and southeast Asia, many species in tribe Xenococcini have been frequently found in Acropyga ants’ nests (
The collector of the species, Mr. Taku Shimada, observed some A. yaeyamensis workers grabbing and carrying the root mealybug individuals by their mandibles when he collected the species (Figure
The author thanks Mr. Taku Shimada, the delegate of AntRoom, Tokyo, Japan, for collecting this new species and providing me with his beautiful photographs of the species and Acropyga yaeyamensis. The author is also grateful to Dr. Éva Szita, Hungarian Academy of Sciences, Hungary, for giving me important literature and Dr. Takumasa Kondo, Corporación Colombiana de Investigación Agropecuaria (CORPOICA), Colombia, for reviewing an earlier version of the manuscript.