Phymastichus holoholo, sp. nov.
Creators: name: Honsberger, David N
name: Wright, Mark G
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Eulophidae
Phymastichus
Phymastichus holoholo

description: Description <i>of Phymastichus holoholo</i> sp. nov. <b>Diagnosis:</b> Among described genera of Tetrastichinae, <i>Phymastichus holoholo</i> falls within the genus <i>Phymastichus</i> as redescribed by LaSalle (1995) given the characters of a swollen parastigma on the forewing; male scape lacking a sensory plaque; scutellum without submedian or sublateral sulci, and anterior pair of setae closer to anterior margin of scutellum than posterior setae (though only slightly in this species); mesoscutum without median sulcus. Overall, females of this species can be distinguished within Tetrastichinae by the combination of the enlarged parastigma and hyaline forewing membrane (Figs 1d; 3a,d); a step-like carina on the syntergum, giving the apex of its gaster a crimped appearance dorsally, with sparse setae on either side of the carina and lacking a distinct tuft of setae posterior to the carina (Figs 1a,b; 2a,b; 3h); the subcubital and cubital setal lines of the forewing distinctly separated until near the apex of the trailing edge of the wing (Figs 1d; 3a,d); coloration and general habitus (Figs 1a; 2). They parasitize the adult stage of some <i>Xyleborus</i> beetles and potentially other Scolytinae as well. <b>Differential diagnosis:</b> Among the other described species of <i>Phymastichus</i>, <i>P. holoholo</i> females can be distinguished from <i>P. coffea</i> by a strong step-like carina on the syntergum (Figs 1b; 3h) (this step-like carina absent in <i>P. coffea</i>); meso- and metacoxae lighter in color than the dark-brown to black body, metacoxae yellow to translucent white (Figs 1a; 2a) (all coxae of similar color to the dark-brown to black body in <i>P. coffea</i>). <i>Phymastichus holoholo</i> females can be distinguished from <i>P. xylebori</i> by the smooth cuticle anterior and posterior to the carina on the syntergum, and few setae medially posterior to the carina (Figs 1a,b; 2a,b; 3h) (scale like sculpture anterior to the carina on the syntergum, and posterior to the carina, a dense tuft of light colored setae extending past the end of the gaster in <i>P. xylebori</i> (Fig. 1e,f)); ovipositor thin and needle-like, usually retracted in dry or alcohol preserved specimens and not visible (Figs 1a–c; 2a) (ovipositor distinctly laterally flattened in <i>P. xylebori</i>, and usually visible in dry or alcohol preserved specimens (Fig. 1e,f)). Both sexes of <i>P. holoholo</i> can be distinguished from <i>P. xylebori</i> by the trailing edge of the forewing, where the cubital and subcubital setal lines of the forewing remain distinctly separate and with no setae between them until approximately the apex of the trailing edge of the wing (Figs 1d; 3a,d) (the cubital and subcubital lines become difficult to distinguish at approximately half the length of the forewing, near the distal apex of the retinaculum in <i>P. xylebori</i> (Fig. 1g)). <i>Female</i> (Figs 1a–d; 2a–c; 3a–c,g,h): <b>Length</b>: 1.2–1.5 mm (Holotype 1.3 mm). Size in general correlates with the size of the beetle host. The length range recorded here is for wasps emerging from the beetles <i>Xyleborus ferrugineus</i> (Fabricius), <i>Xyleborus affinis</i> Eichhoff, and <i>Xyleborus perforans</i> (Wollaston), the currently confirmed hosts. If this wasp uses hosts other than these beetles, its size is expected to vary according to the size of the beetle, and may fall outside this range. <b>Head</b>: Cuticle dark brown and shiny, with lightly reticulate sculpture visible under high magnification. Toruli located just above level of lower edge of eyes, scape reaching approximately to the level of the anterior ocellus. Scrobal depression shallow, its lateral edges smoothly rounded. Scrobal depression an inverted heart shape, widest at the toruli and tapering to a point below the anterior ocellus, a small triangular shaped interscrobal crest protruding between the toruli and reaching to approximately the level of the top of the toruli. The floor of the scrobal depression evenly rises to a shallow medial elevation that runs from the apex of the depression to the interscrobal crest. Frontofacial sutures consisting of two thin white lines, beginning at the outer margin of the two posterior ocelli and converging at the apex of the scrobal depression. Note that in air dried specimens much of the face from above the clypeus to the ocelli, including the entire scrobal area, is almost always collapsed and many of these characters are obscured. Antennae with scape, pedicel, a single anellus, 3 funicular segments, and a 3-segmented clava. Pedicel and flagellomeres apical of the anelli dark brown, similar in color to body, the scape lighter in color. The anellus typically appears more yellow than the rest of the antennae, and the pedicel can also be lighter in color than the flagellum in some individuals. Flagellum setose, and with sensilla including four apically converging terminal sensillar projections on the last segment of the clava that can be seen under high magnification. Setae on the pedicel and flagellum angled about 30–45 degrees from the apical direction of the antenna, and approximately 1/2 to 2/3 as long as the funicular segments are wide. Scape also setose, though the setae are shorter and thinner than on the pedicel and flagellum, and with a flattened area ventrally to receive the rest of the antenna when folded. Funicular segments longer than wide. Ratio of the length of the antennal segments, not including the anellus, approximately Scape: Pedicel: F1: F2: F3: F4: F5: F6 = 2.2: 1.2: 1.0: 0.9: 1.0: 0.8: 0.7: 0.5. Eyes red to black with sparse, very small, short setae. Ocelli positioned in the form of an obtuse triangle, posterior ocelli closer to compound eyes than to each other, cuticle of the ocellar triangle raised relative to the rest of the vertex. Setae short on vertex, longer and of similar density on the face, shorter and of higher density on occiput. Margins of clypeus not delimited by a suture, but its upper corners with an anterior tentorial pit on each side. Malar sulcus complete. Mandibles tridentate and symmetrical, the ventral tooth pointed but not sharply, the middle tooth broadly rounded, the dorsal tooth differentiated from the overall curvature of the inner edge of the mandible by a small notch. <b>Mesosoma:</b> Cuticle, with the exception of the legs (see below) and tegula which are typically translucent yellow, dark brown to black and shiny with light reticulate sculpture visible under high magnification. Pronotum with a transverse row of posterior pointing setae near the border with the mesoscutum, except near the midline which is free of setae, the first one or two setae lateral of the midline longer than the others. Additional setae often present anterior to this row. Mesoscutum lacking a medial sulcus on cuticle surface, and with three adnotaular setae, the anterior one approximately even with most anterior reach of the axillae, the two posterior setae near the scutellum, close together, and longer than the anterior seta. Mesoscutum mesal of notauli otherwise free of setae. Mesoscutal lateral lobe with setae pointing in various directions, of similar density to those on the posterior region of the pronotum. Scutellum with two pairs of setae near the lateral margins of the disk, one pair slightly anterior of the middle and the other pair near the posterior margin, a pit also present between the anterior and posterior setae. Lateral to the scutellar disk, the scutellum transitions smoothly to the impressed axillula where the cuticle is slightly wrinkled but lacks the set of distinct carinae present in <i>P. xylebori</i>. Propodeum strongly indented posteriorly to receive the small petiole, its margin also slightly concave where it comes up against the dorsellum. Median propodeal carina present but wide and somewhat inconspicuous. Plicae absent, callus with setae posterior and lateral to the spiracle, including on the convex region where the inclination of the sclerite becomes almost vertical. <b>Legs:</b> Yellow to translucent yellow below coxae, though in some individuals the femora also have a black tint. Procoxae dark brown to black, similar in color to the body. Meso- and metacoxae translucent yellow, often lighter in color than the rest of the leg. Mildly curved tibial spurs on all legs. Tarsi and tibiae setose, femora with some setae but largely bare. Pro- and mesofemora of similar shape and thickness, metafemur substantially thicker. First through third tarsal segments subequal in length in all legs, fourth not including the pretarsus slightly longer. Tarsal claws brown in color, more robust in the mid and hind legs than in the foreleg. <b>Wings:</b> Forewing: Parastigma slightly to distinctly swollen, as is characteristic for this genus. Cubital and subcubital setal lines join near the apex of the trailing edge of the wing, though the non-setose region between them becomes narrower distal to the retinaculum. Postmarginal vein protrudes only slightly if at all from the junction of the marginal and stigmal veins, and is much shorter than the stigmal vein. Marginal and submarginal veins subequal in length. Submarginal vein usually with three strong dorsal setae, and other smaller setae on the membrane anterior to the vein. Marginal vein with many strong setae. Veins somewhat uniformly yellow-brown in color, except for the stigmal vein which is transparent basal of the stigma. Stigma yellow-brown, and uncus present with four sensilla. Membrane subhyaline, apical of the small speculum and anterior to the cubital setal line covered approximately evenly over its surface with short setae. These setae are uniformly produced on the dorsal surface of the wing. On the ventral side, in the apical region of the wing they are similar in length to those on the dorsal side, but become strongly reduced in the medial and basal regions, especially closer to the trailing edge. Hindwing: Membrane hyaline, the density and size of setae on the dorsal surface similar to that of the forewing; setae on the ventral surface reduced to dark spots. Trailing edge with long marginal setae consistently about 2/5 the maximum width of the hindwing. Veins yellow-brown in color. Three hamuli spaced closely together extend forward from the venation near its apex. <b>Gaster:</b> Cuticle shiny dark brown to black, with somewhat reticulate sculpture visible under high magnification. Each gastral segment except the last with a transverse line of setae, setae longer and more upright on posterior segments. Gaster with hypopygium often distinct in dried specimens, extending near to the end of the gaster, cavernous posteriorly. The hypopygium is, however, not clearly distinguished in some individuals, and the shape of the gaster as a whole can vary. Relative to the rest of the gaster, setae increase in density on the hypopygium around the margins of the cavity and on the ventral part of the gaster posterior to the hypopygium. Syntergum with distinct step-like carina, similar to that of <i>P. xylebori</i>, giving the very end of the gaster a crimped appearance. Cerci located directly posterior to the carina. Anterior to the carina, the cuticle is smooth, without scale-like sculpture as in <i>P. xylebori</i>, and medially free of setae. Posterior to the carina, the cuticle is also smooth and shiny, the same color as the rest of the gaster and with at most a few short setae medially, free of long setae other than those emerging from the cerci. Ovipositor almost always retracted and only rarely projecting in dry or alcohol preserved specimens, but if visible, straight and needle-like, not especially flattened laterally in cross section as it is in <i>P. xylebori</i>. <i>Male</i> (Figs 2d–f; 3d–f): Similar in overall shape and coloration to female, but with the following differences: <b>Size:</b> 0.7–0.8 mm long (Allotype 0.75 mm). Typically much smaller than the females, and always smaller than a female emerging from the same host beetle. <b>Head</b> as in female except: Antennae substantially thinner than in the female and with one more flagellar segment, consisting of scape, pedicel, a single anellus, and 7 flagellomeres, the last 3 of which form a clava. Ratio of the length of the antennal segments, not including the anellus, is approximately Scape: Pedicel: F1: F2: F3: F4: F5: F6: F7 = 2.9: 1.8: 1.0: 1.0: 1.1: 1.3: 1.2: 1.1: 0.8. Antennae setose and with sensilla, setae longer than the width of the funicular segments. Last antennal segment ends in a single terminal sensillum. As in the two other known species of <i>Phymastichus</i>, and unlike all other known members of Tetrastichinae, males lack a ventral sensory plaque on the scape. <b>Mesosoma</b> as in female except: <b>Legs</b> with all coxae dark brown at least basally and medially, of similar color to the body, often lighter apically; femora and tarsi also typically somewhat darker than in the female, though this varies among individuals. <b>Wings</b> similar in overall structure to female except forewing with parastigma somewhat swollen but variable and typically not as swollen as in the female; submarginal vein often with only two long setae in addition to shorter setae. <b>Gaster:</b> Overall somewhat oval in shape in dorsal view; setae in a similar pattern though overall less setose than in females; last tergite free of setae except for those emerging from the cerci. Repositories UHIM—University of Hawaiʻi Insect Museum, Honolulu, Hawaiʻi, USA BPBM—Bernice Pauahi Bishop Museum, Honolulu, Hawaiʻi, USA NHMUK—The Natural History Museum, London, UK <b>Holotype:</b> Oʻahu, Kahana Bay (21.5573 N, - 157.8783 E, 15 m), 22.vii.2020, &amp;female;, ex <i>Xyleborus</i> beetles from <i>Schefflera actinophylla</i> (deposited in UHIM). <b>Allotype:</b> Oʻahu, Kahana Bay (21.5573 N, - 157.8783 E, 15 m), 22.vii.2020, &amp;male;, ex <i>Xyleborus</i> beetles from <i>Schefflera actinophylla</i> (UHIM). <b>Paratypes:</b> Oʻahu, Kahana Bay (21.5573 N, - 157.8783 E, 15 m); 10.ix.2020; 11 &amp;female;, 2 &amp;male;; ex <i>Xyleborus</i> beetles from <i>Schefflera actinophylla</i>; (6 &amp;female;, 2 &amp;male; UHIM; 5 &amp;female; BPBM) • Oʻahu, Kahana Bay (21.5573 N, - 157.8783 E, 15 m); 22.vii.2020; 18 &amp;female;, 5 &amp;male;; ex <i>Xyleborus</i> beetles from <i>Schefflera actinophylla</i>; (8 &amp;female;, 1 &amp;male; UHIM; 5 &amp;female;, 2 &amp;male; BPBM; 5 &amp;female;, 2 &amp;male; NHMUK) • Oʻahu, Kahana Bay (21.5604 N, - 157.8765 E, 15 m); 31.i.2020; 3 &amp;female;, 2 &amp;male;; ex <i>Xyleborus ferrugineus</i> from <i>Mangifera indica</i>; (UHIM) • Hawaiʻi island, ʻ&amp;Amacr;hualoa; 30.x.2019; 1 &amp;female;, 1 &amp;male;; ex <i>Xyleborus perforans</i> from <i>Macadamia integrifolia</i>; (UHIM) • Hawaiʻi island, Keaʻau; 1.xi.2019; 4 &amp;female;, 4 &amp;male;; ex <i>Xyleborus ferrugineus</i> from <i>Macadamia integrifolia</i>; (2 &amp;female;, 2 &amp;male; UHIM; 1 &amp;female;, 1 &amp;male; BPBM; 1 &amp;female;, 1 &amp;male; NHMUK) • 2 &amp;female;, 1 &amp;male;; same data as previous except ex <i>Xyleborus affinis</i> from <i>Macadamia integrifolia</i>; (BPBM) • 1 &amp;female;, 1 &amp;male;; same data as previous except ex <i>Xyleborus perforans</i> from <i>Macadamia integrifolia</i>; (NHMUK) • Oʻahu, M&amp;amacr;noa valley (21.3293 N, - 157.7972 E); 15.ix.2020; 3 &amp;female;, 4 &amp;male;; ex <i>Xyleborus affinis</i> from <i>Cecropia obtusifolia</i>; (1 &amp;female;, 1 &amp;male; UHIM; 1 &amp;female;, 2 &amp;male; BPBM; 1 &amp;female;, 1 &amp;male; NHMUK). <b>Etymology.</b> This wasp strolls along the surface of wood to search for its hosts. The species name is Hawaiian, meaning “to go out for a walk or to see the sights” and is to be treated as an indeclinable noun in apposition. Biology Known host range <i>Phymastichus holoholo</i> <b>sp. nov.</b> has been reared from <i>Xyleborus ferrugineus</i>, <i>X. perforans</i>, and <i>X. affinis</i> adult beetles in octopus tree (<i>Schefflera actinophylla</i>) in the Kahana Bay area of Oʻahu; the same three beetle species in macadamia (<i>Macadamia integrifolia</i>) in the areas of ʻ&amp;Amacr;hualoa, Kapaʻau, and Keaʻau on the island of Hawaiʻi; from <i>X. ferrugineus</i> in mango (<i>Mangifera indica</i> L.) branches in the Kahana Bay area of Oʻahu; and from <i>X. affinis</i> in trumpet tree (<i>Cecropia obtusifolia</i> Bertol.) branches near the upper reaches of M&amp;amacr;noa valley on Oʻahu. Emergence holes on the elytral declivity of the beetle, typical for this genus as observed in LaSalle (1995), Espinoza <i>et al.</i> (2009), and the present study, were found on two Hawaiian endemic <i>Xyleborus lanaiensis</i> Perkins beetles extracted from a fallen ‘&amp;amacr;laʻa (<i>Planchonella sandwicensis</i> (A. Gray) Pierre) tree in the Waiʻanae mountains of Oʻahu (Fig. 4i). We expect these beetles were parasitized by <i>P. xylebori</i> or <i>P. holoholo</i>, or perhaps another unknown <i>Phymastichus</i> species, but cannot know with certainty whether one or both of these species include any members of the Hawaiian endemic radiation of <i>Xyleborus</i> beetles in their host range. Hundreds of <i>X. lanaiensis</i> individuals were collected from the same tree and no emergence of parasitoids was observed, suggesting the percent parasitism of these beetles at this location in this tree was low. Another similar emergence hole was also found on an <i>X. ferrugineus</i> beetle in <i>Acacia koa</i> A.Gray on Waʻahila Ridge on Oʻahu, though again we do not know by which species it was parasitized. We also observed two species of Scolytinae that this wasp may use under some circumstances but does not seem to prefer, at least in the environments we have observed it so far. An emergence hole typical of <i>Phymastichus</i> was found on a single <i>Xylosandrus</i> <i>crassiusculus</i> Motschulsky beetle inhabiting the octopus tree branches used in the calculation of percent parasitism (described later) (Fig. 4j). Since all wasps emerging from beetles within this wood were <i>P. holoholo</i> we assume the beetle was parasitized by this species,. Though <i>X. crassiusculus</i> is a somewhat common inhabitant of the octopus tree wood in that area, and we have extracted a good number of individuals from those trees during this study (in excess of 100), this is the only individual we have seen that was clearly parasitized. Though <i>Euwallacea fornicatus</i> (<i>sensu lato</i>) beetles are also common inhabitants of the octopus tree wood from which we found this species emerging, we have not observed any individuals with a parasitoid emergence hole. <i>Phymastichus holoholo</i> individuals have also been observed to actively walk over <i>E. fornicatus</i> (<i>sensu lato</i>) beetles naturally infesting octopus tree wood without showing any sign of interest, while showing substantial interest in and parasitism of <i>Xyleborus</i> beetles in the same stage of infestation. Despite this, two instances of parasitism have been observed in dissected <i>E. fornicatus</i> (<i>sensu lato</i>) individuals: one parasitoid larva, confirmed by molecular analysis to be <i>P. holoholo</i>, and one seemingly developed adult that eclosed but had not yet emerged from the beetle, were found inside beetles extracted from naturally infested octopus tree wood and identified by DNA sequences as <i>E.</i> <i>perbrevis</i> (Schedl) and <i>E.</i> <i>fornicatus</i> (Eichhoff), respectively (using the primers of Folmer <i>et al.</i> (1994); the CO1 gene matched with specimens on GenBank referenced in Smith <i>et al.</i> (2019)). Thus at least some <i>P. holoholo</i> individuals may under some circumstances take marginal interest in members of this species complex and are able to complete their develo
description: Published as part of <i>Honsberger, David N &amp; Wright, Mark G, 2022, A new species of Phymastichus (Hymenoptera: Eulophidae: Tetrastichinae parasitic on Xyleborus beetles (Coleoptera: Curculionidae: Scolytinae) in Hawaiʻi and aspects of its biology, life history, and behavior, pp. 107-122 in Zootaxa 5116 (1)</i> on pages 109-118, DOI: 10.11646/zootaxa.5116.1.5, http://zenodo.org/record/6366455
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