Acerocephala hanuuanamu Honsberger & Lorenzo-Elarco, 2024

Honsberger, David N., Honsberger, Maya, Lorenzo-Elarco, J. Hau‘oli & Wright, Mark G., 2024, The genus Acerocephala and observations of the life history of Acerocephala hanuuanamu sp. nov. (Hymenoptera, Cerocephalidae) and its bark beetle host on the island of O‘ahu, Hawai‘i, Journal of Hymenoptera Research 97, pp. 545-589 : 545-589

Acerocephala hanuuanamu Honsberger & Lorenzo-Elarco sp. nov.

Figs 1 , 2 , 3 , 10 a

Diagnosis.

Females of this species can be distinguished from other known Acerocephala by the antenna with the first four funicular segments transverse and of similar size and shape, followed by a larger and subcircular fifth segment and the clava; interantennal ridge flush with face, not elevated in lateral view, and only slightly widened anteriorly; scrobes reaching more than half the length of the head; submarginal and marginal veins of forewing join smoothly with no callus; clypeus, to its apex, fills the space between the mandibles when mandibles are closed. Males are similar to females in characters of the head with the exception of the antennae, so can be distinguished from other known species by these characters as well.

Differential diagnosis.

Females are easily distinguished from A. atroviolacea , A. aenigma , and A. pacifica by the first four funicular segments much smaller and shorter than the fifth; overall gracility of the head and body; interantennal ridge not elevated from the face in lateral view ( A. atroviolacea , A. aenigma , and A. pacifica with fifth funicular segment of similar size to preceding segments; body and head thicker and more robust; interantennal ridge elevated from the face in lateral view); and from A. atroviolacea and A. aenigma by lack of callus on the forewing ( A. atroviolacea and A. aenigma with callus present).

A. hanuuanamu is closest to A. ihulena sp. nov. and A. indica . Females can be distinguished from A. ihulena and A. indica by interantennal ridge not elevated from the face in lateral view; first four funicular segments of similar size and distinctly smaller than the fifth; ovipositor sheaths only slightly exerted, extending less than 1 / 3 the length of the gaster; scutoscutellar grooves foveolate and meeting the transscutal articulation lateral of medial line ( A. ihulena and A. indica with interantennal ridge elevated from the face in lateral view; fourth funicular segment slightly but distinctly larger than the first three; ovipositor sheaths distinctly exerted from the gaster, near half its length, dark brown at the apex and lighter near the base; scutoscutellar grooves a subcircular sulcus that reach the transscutal articulation mesally).

Description.

Female (Figs 1 , 2 a – d , 3 a – c, e – j , 10 a ; morphometric measurements in Suppl. material 1). Length: Variable, depending on size of host. On C. brasiliensis individuals range from 1.18–2.31 mm (Holotype 1.96 mm), the largest individual collected was 2.50 mm from C. mangiferae , a slightly larger beetle.

Coloration: Head brown; slightly lighter anteriorly in lower face, basal part of mandibles, and scape and pedicel. Mesosoma brown, prothorax and apex of propodeum often somewhat lighter. Petiole yellow. Gaster dark brown except basoventrally where it is light brown, and the ovipositor sheaths which are light brown. Legs yellow-brown, pro- and metacoxae somewhat lighter in color than their respective tibiae.

Head: Head subrectangular in full face view; more or less parallel sided, subtly widest across eyes, of nearly equal width at about half its length, and tapers very slightly to the anterolateral corner. Anterior of head, excluding the mandibles and projected clypeus, a strongly concave arc. Clypeus projected medially, subrectangular with slightly rounded base and longer than wide, to its apex occupies all the lateral space between the mandibles when mandibles are closed. Interantennal ridge flush with the face lateral of scrobes, not elevated dorsally from the face in lateral view; its anterior half, to about even with where the scrobes narrow, laterally carinate, dorsally smooth and slightly convex between the carinae; posterior to this non-carinate, more narrowly and evenly rounded, along the median line joining smoothly with the upper face. Lateral margins of scrobal depression just above the toruli extend approximately half the width of the face, lateral margins distinctly taper and at about half the length of the interantennal ridge where its carina ends; anterior of this the lateral margins are lightly carinate and the depressions deeper; posterior to this with rounded margins and the depressions become progressively narrower and shallow before they join with the upper face. Mandibles long and curved with three apical teeth; dorsal and middle tooth of a similar conical shape but with a deep groove between them, middle tooth projecting slightly more than dorsal tooth, ventral tooth projecting about twice this much relative to the middle tooth. Bottom of toruli adjacent to the dorsoventrally inclined arc that comprises the anterior of the face. Occipital carina just posterior to posterior ocelli, subcircular. Dorsal side of the face with smooth and shiny texture and with sparse setae, the setae increase slightly in length and density anteriorly, more densely placed short setae around the occipital carina. Ventral side of head generally flat with some longer setae posteriorly, median suture extends longitudinally from the mouthparts to the occipital carina, basal area near the suture indented slightly for about 2 / 5 the length of the head, the cuticle in this indent with reticulate texture, cuticle on ventral side of face otherwise smooth and shiny.

Antennal flagellum composed of 5 funicular segments and a subconical clava. First four funicular segments transverse cylindrical and of similar size and shape, 5 th funicular segment subspherical and larger than the first four, clava is approximately 1.4 times as long as the first four flagellar segments, rounded subconical. All antennal segments with thin setae projecting at approximately 45 degrees, the first four funicular segments with a single whorl of setae of length slightly less than the width of the segments, setae becoming progressively shorter towards the apex of the antenna. The 5 th funicular segment with MPS and the clava with three whorls of MPS; the first four flagellar segments lack MPS. Mean length / mean width (Ratio) of antennal segments, length and width measured relative to length of F 1 (n = 12): Scape 6.0 / 2.3 (2.7); Pedicel 3.4 / 1.7 (2.0); F 1 1.0 / 1.5 (0.7); F 2 0.9 / 1.5 (0.6); F 3 1.0 / 1.6 (0.6); F 4 1.1 / 1.8 (0.6); F 5 2.5 / 3.0 (0.8); Clava 6.5 / 4.1 (1.6).

Mesosoma: Long prothorax articulates with mesothorax, rotating from in line with the rest of the mesosoma to approximately 110 degrees. A light longitudinal carina present laterally on pronotal neck, pronotum otherwise smooth, lacking a transverse pronotal carina. Pronotal neck and collar smooth, collar with scattered mesal pointing setae except on its dorsal surface near the medial line where there are no setae. In dorsal view, pronotum very slightly widest near its middle, but at its widest distinctly narrower than the mesonotum. Transscutal articulation deep and well defined, straight until the lateral section where the sclerites incline vertically. Notauli and scutoscutellar suture both foveolate and visible relative to the otherwise smooth and shiny mesonotum, marked by punctures and a mild sulcus, setae on either side of the sutures, the notauli deepening anteriorly and giving the mesonotum a shouldered appearance. Lateral of the median line, notaulus and scutoscutellar suture meet the transscutal articulation at approximately a 45 degree angle and at approximately the same point, so the medial lobe of the mesoscutum and the scutellum run up against each other for a distance (see morphometric measurements). In dorsal view, scutoscutellar sutures are fairly straight until they meet the transscutal articulation, notauli are mildly curved. Posterior margin of scutellum evenly convex. Mesonotum smooth and glassy, free of setae except on either side of the notauli and on either side of the scutoscutellar suture, a few scattered setae on the axillae, and near posterior margin of the scutellum. Metanotum visible behind scutellum. Propodeum slightly wrinkled at its anterior margin and on the callus anterior of the spiracle, otherwise smooth and glassy, flat longitudinally and lightly rounded transversely. Propodeal spiracle slightly recessed in a small depression, paraspiracular sulcus a very slight and smoothly rounded depression continuing from the spiracular depression posteromedially and gradually fading. Sides of the propodeum slightly tapering posteriorly until above attachment of the rear coxae, where they abruptly taper to about 60 degrees from the anteroventral line, then curve to be slightly more longitudinally oriented toward their apex at the nucha, top of petiolar insertion flush with dorsal surface of propodeum. Setae near the lateral margins of propodeum: on callus anterior of the spiracle, on lateral margin where callus meets the metapleuron, and just above where the propodeum accommodates the hind coxal foramen. Mesopleuron with light reticulate texture, mesepisternum with setae.

Wings: Forewing: Length of marginal vein approximately 1.15 × length of submarginal vein. Short postmarginal vein extends to approximately even with the stigma or somewhat less. Stigmal vein projects from marginal vein at slightly less than 45 degrees and has a slight curve apically. Three dorsal setae on marginal vein, basal one small and inconspicuous. Marginal setae begin at the base of marginal vein and continue around apex of wing with approximately consistent length to trailing edge approximately even with stigmal vein, just apical of retinaculum. Parastigma not swollen, submarginal and marginal veins joining smoothly and unperturbed with no swollen area or change in pigmentation; lacking any sign of a tuft of setae on the parastigma. Membrane subhyaline with slightly rippled texture and without setae; basally to end of venation lightly infuscated, the area near and posterior to stigma most shaded.

Hindwing: Venation with a concavity at approximately half the distance from the base to the hamuli, venation hyaline at the culmination of this concavity; anterior margin of wing membrane extends more or less straight in this region so at the apex of the concavity the venation reaches nearly ½ the distance to the posterior of the wing membrane. Venation ends at the hamuli but the very anterior of the membrane in line with venation remains somewhat pigmented beyond the hamuli, to approximately 2 / 3 the length of the wing. Marginal setae present from the end of this pigmented region around to base of trailing edge of wing, longest around trailing edge where they are approximately ¾ the maximum width of the wing.

Legs: Fore and rear coxae globose, subequal in size and shape though the fore coxa hides somewhat under the pronotum. Femora also globose, slightly larger than their respective coxae in the front and mid, legs, subequal in the back leg. Tibiae of similar length to their respective femora, also globose apically, but narrower basally. In all legs, first tarsal segment longest, 2 nd through 4 th segments sequentially decrease in length; 5 th segment not including the claw intermediate between 1 st and 2 nd in front and middle legs, subequal to 2 nd in back legs. Protibial spur deviates from straight with a jog of shape similar to a logistic function, its base set back on the tibia and extending just past base of first tarsal segment, tibia beneath the spur with protibial comb. Midleg and back leg with narrower, straight protibial spur extending from near the apex of the segment. Fore and midleg with the two basal tarsi of each leg spinose, spines fading on the apical segments; hindleg with spines smaller except for those at the apex of the tarsal segments. Tibiae with narrow setae and no additional spines, except for the very apex of the back leg.

Metasoma: Petiole somewhat globose-vase shaped, the widest point marked by one or two lateral setae on a small knob; somewhat flat dorsally, overall of subequal length and width. First and second gastral segments emarginate medially, subsequent segments with straight posterior margin. Gaster in living individuals expands and contracts during feeding, use of the ovipositor, and movement; therefore the following applies to dried individuals. 1 st and 4 th gastral tergites longest, 3 rd slightly shorter, 2 nd substantially shorter than 3 rd; 5 th very short; 6 th subequal in length to 2 nd. Gaster not heavily sclerotized, shrivels slightly on drying. Gaster with few, small setae on first five segments, 6 th with many setae, some short, some longer than the exserted ovipositor sheath, but rarely reaching past it due to their angle. Ovipositor sheaths also setose, and are slightly exserted; ovipositor thin and needle-like.

Male (Figs 2 e – h , 3 d ; morphometric measurements in Suppl. material 1). Length: Typically, but not always, smaller than females developing in the same colony of hosts. As with the female, size depends on the size of the host, but the smallest individuals are nearly always male. Very variable, from 0.83–1.65 mm (allotype 1.60 mm).

Similar to female except: Wingless. Antennae with 6 funicular segments, similar to that of female except that the four similarly shaped basal flagellar segments in the female are five in the male, the sixth larger and subcircular; clava with two whorls of MPS. Mean length / mean width (Ratio) of antennal segments, length and width measured relative to length of F 1 (n = 7): Scape 6.5 / 2.4 (2.7); Pedicel 3.7 / 1.8 (2.1); F 1 1.0 / 1.4 (0.7); F 2 1.1 / 1.5 (0.8); F 3 1.1 / 1.6 (0.7); F 4 1.2 / 1.8 (0.7); F 5 1.4 / 2.1 (0.7); F 6 2.1 / 2.9 (0.7); Clava 5.3 / 3.7 (1.5). Ocelli absent and compound eye smaller than in female, morphometrics of face otherwise similar, mandibles similar. Posterior region of pronotum tapers slightly to fit around the narrower medial lobe of the mesoscutum. Notauli nearly meet on the medial line at the transscutal articulation, scutoscutellar suture meets transscutal articulation lateral to this, similar to the female. Pro- and mesoscutum smaller than in female, scutellum much shorter than in female, metanotum behind it appears in dorsal view nearly straight with nearly parallel anterior and posterior margins. Femora, tibiae, and tarsal segments somewhat stouter than in female, but their relative lengths remain similar. Posterior margin of propodeal disk with scattered setae. Gaster shorter, apically truncated-looking in dry specimens.

Materials examined.

Holotype (Fig. 2 a – d ): ♀; Hawaiian Islands, O‘ahu, Mānoa ; 21.2946 ° N, 157.8136 ° W; 2. viii. 2022; below bark of Ficus microcarpa branch (deposited in UHIM).

Allotype (Fig. 2 e – h ): ♂; Hawaiian Islands, O‘ahu, Mānoa ; 21.2946 ° N, 157.8136 ° W; 2. viii. 2022; below bark of Ficus microcarpa branch ( UHIM).

Paratypes: 65 ♀, 54 ♂. Hawaiian Islands, O‘ahu, Mānoa ; 21.2946 ° N, 157.8136 ° W; 2. viii. 2022; below bark of Ficus microcarpa branches; 57 ♀, 52 ♂ (19 ♀, 18 ♂ UHIM; 19 ♀, 17 ♂ BPBM; 19 ♀, 18 ♂ NMNH) • Hawaiian Islands, O‘ahu, Mānoa ; 21.3060 ° N, 157.8092 ° W; 15. xii. 2020; below bark of Artocarpus altilis branch; 2 adult ♀ and 1 pupa glued to point ( UHIM) • Hawaiian Islands, O‘ahu, Mānoa ; 21.5604 ° N, 157.8765 ° W; 31. i. 2020; below bark of Mangifera indica branches; 3 ♀, 1 ♂ (1 ♀, 1 ♂ UHIM; 1 ♀ BPBM; 1 ♀ NMNH) • Hawaiian Islands, O‘ahu, Mānoa ; 21.2954 ° N, 157.8145 ° W; 27. vii. 2018; below bark of Ficus microcarpa branches; 3 ♀, 1 ♂ (1 ♀, 1 ♂ UHIM; 1 ♀ BPBM; 1 ♀ NMNH) .

Other materials examined.

Hawaiian Islands, O‘ahu, Mānoa ; 21.2952 ° N, 157.8141 ° W; 3. xii. 2020; below bark of Trema orientalis branch; wasp ex tunnels inhabited by the beetle; 1 ♀ and 1 C. brasiliensis adult glued to point ( UHIM) .

Etymology.

The species name is Hawaiian, hanu‘uanamū (lit., flowing between caves of the insect). This species constructs a feeding tube to host-feed through the walls of the pupation chamber constructed by its host. Hanu‘u represents the continuous action of ebb, flow, and exchange of fluid through the connection bridging the cavern (ana) and the wasp, and ana mū recognize the system of tunnels and caverns constructed by the host insect (mū), reminiscent of lava chambers.

Known distribution.

This species is known from the island of O‘ahu in Hawai‘i, where it is likely adventive.

Known hosts.

Cryphalus spp. , including C. brasiliensis and C. mangiferae .

Figures

Figure 1. Acerocephala hanuuanamu sp. nov. (paratypes) showing morphometric measurements. Acronyms explained in text. Scale bars: 1 mm (b, c); 500 μm (a).

Figure 2. Acerocephala hanuuanamu sp. nov. holotype ♀ (a – d) and allotype ♂ (e – h) a, e side view b, f head c, g anterior view of head showing mandibles d, h dorsal view. Scale bars: 1 mm (a, d, e, h); 250 μm (b, c, f, g).

Figure 3. Acerocephala hanuuanamu sp. nov. a forewing ♀ b hindwing ♀ c antenna ♀ d antenna ♂ e dorsal view ♀ (paratype) f head ♀ (paratype) g anterior view of head showing mandibles ♀ (paratype) h foreleg ♀ i midleg ♀ j hindleg ♀. Scale bars: 1 mm (e); 250 μm (f, g).

Figure 10. Acerocephala hanuuanamu, Cryphalus brasiliensis, and the phloem sandwiches a A. hanuuanamu ♀ b C. brasiliensis ♀ c parts of phloem sandwich style observation chamber d phloem sandwich with colonies of C. brasiliensis in F. microcarpa wood e, f closeups of additional phloem sandwiches.