Adelges (Dreyfusia) densae Havill & Brunet, 2025

Havill, Nathan P., Brunet, Bryan, Zembrzuski, Zephyr & Tshering, Kaka, 2025, Four new adelgid (Hemiptera: Adelgidae) species from Bhutan, including the first legless species of Aphidomorpha, Zootaxa 5583 (3), pp. 437-461 : 453-455

Adelges (Dreyfusia) densae Havill & Brunet , sp. nov.

( Fig. 6A–C )

Etymology. Genitive derived from its host plant, Abies densa .

Type material. HOLOTYPE: 1 adult exulis, BHUTAN, Bumthang, Tangsibi, lat. 27.4972, long. 90.8699, 6- IV-2022, on Abies densa, Kaka Tshering ( USNM) . PARATYPES: 1 first instar exulis ( CNC#5338332-12 ) , same data. 2 late instar nymph exules, same data ( NBC) . 1 first instar exulis, 2 late instar nymph exules, same data ( USNM) . 1 first instar exulis, same data ( YPM # ENT594781 ) . 2 late instar nymph exules, same data ( YPM # ENT594788 ) .

Additional material examined. BHUTAN: Bumthang: Tangsibi: 2 first instar exules, 11 late instar nymph exules ( CNC), 1 first instar exulis, 2 first instar exulis exuviae, 10 late instar nymph exules ( NBC), 4 first instar exules, 6 first instar exulis exuviae, 2 late instar nymph exules ( USNM), 8 first instar exules, 17 first instar exulis exuviae, 14 late instar nymph exules, 2 late instar nymph exulis exuviae ( YPM), lat. 27.4972, long. 90.8699, 6-IV-2022, on Abies densa, Kaka Tshering .

Diagnosis. The first instar exulis of A. (D.) densae ( Fig. 6A ) is similar to Adelges (Aphrastasia) pectinatae ( Cholodkovsky, 1888) , A. (Ap.) pindrowi Yaseen & Ghani, 1971, A. (D.) nordmannianae , and Adelges (D.) piceae (Ratzeburg, 1844) in having compound wax glands with emarginated clusters of many small facets. It differs from these species in the structure of the wax glands, and that the first instar exulis has wax glands in pleural and lateral positions. Late instar exulis nymphs ( Fig. 6B ) are similar to the adult ( Fig. 6C ) but lack an ovipositor.

Description. First instar exulis. ( Fig. 6A ). Body length: n = 10, 0.431 –0.588 (0.494) mm. Body width: n =11, 0.271 –0.457 (0.335) mm. Dorsal wax glands generally on strongly sclerotized plates. Glands consist of 2–6 round, oval, or polygonal delineated areas arranged around a central seta, each area containing approximately 6–50 very small round, oval, or polygonal facets, sometimes glands merged, arranged around two or more setae.

Head and pronotum with moderately to strongly sclerotized and reticulated spinal and lateral plates, separated from each other and along mid-line by wide fissures. Ocelli borne on separate lateral plates. Each spinal cephalic plate with six large wax glands, two spinal, two lateral, two apical, together filling most of the area of the plate. Ventral wax glands at base of antennae lacking. A pair of spinal flagellate setae on head slightly less than half the distance from apex. Antennae 3-segmented, segment III imbricated, length [n = 13, 0.076 –0.089 (0.083) mm], approximately 5.2x its width at midpoint [n = 13, 0.013 –0.020 (0.016) mm], and approximately 2.1x longer than segments I [n = 12, 0.016 –0.028 (0.021) mm] and II [n = 12, 0.017 –0.022 (0.019) mm] combined. Two primary rhinaria on segment III, one subapical and one approximately ½ the segment length from the apex, each with a small thumb-like projection. Several accessory rhinaria adjacent to subapical primary rhinarium. Processus terminalis with five setae, the apical seta length [n = 5, 0.033 –0.037 (0.034) mm] approximately 3.0x longer than the rest. Rostrum reaching hind coxae, with ultimate segment 0.7x as long [n = 11, 0.033 –0.038 (0.036) mm] as width of segment III at midpoint [n = 11, 0.045 –0.052 (0.050) mm]. Stylet length [n = 4, 1.811 –1.959 (1.888) mm] approximately 3.8x body length.

Coxae and femorotrochanters smooth, with tibiae and second tarsal segments weakly imbricated. Pair of dorso-subapical capitate setae, subequal in length, on tarsal segment II of fore-, mid- and hindlegs. Wax glands antero-lateral to mid-coxae with approximately 7–12 round to oval facets. Hind femorotrochanter length: n = 13, 0.056 – 0.068 (0.063) mm.

Pronotum with wax glands on the four corners of each spinal plate, each gland with 4–6 facet areas. Lateral prothoracic plates longitudinal oval-shaped, each with 2 wax glands, each gland with 5–6 facet areas. Meso- and metathorax with separate lateral, pleural, and spinal plates, lateral plates with wax gland with 5–6 facet clusters arranged around 1–2 setae, pleural and spinal plates each with a single wax gland with 4–5 facet clusters arranged around one seta.

Each abdominal plate generally with a single wax gland with 2–4 faceted areas surrounding a seta. Abdominal segments I–V with separate lateral, pleural, and spinal wax plates, segment VI–VII with lateral and spinal plates, spinal plates touching or fused at the midline, segment VIII with very small lateral plates lacking wax glands, segment IX with apical plate lacking wax glands. Abdominal segments VII–IX tend to collapse telescopically when slide mounted, making these segments easier to see in exuviae. Lateral abdominal plates ovoid to square, pleural and spinal plates transverse oval. Abdominal segment IX with a pair of flagellate setae at the tip.

Adult exulis. ( Fig. 6C ). Body length: n = 1, 1.305 mm. Body width: n = 1, 0.770 mm. Moderately to strongly sclerotized dorsal plates generally bearing large, strongly sclerotized hemispheroid protuberant spinal and pleural plates with 1–3 stout setae on the surface and bearing no apparent wax glands.

Head and pronotum with lightly sclerotized large spinal and small lateral plates, separated from each other and along mid-line by fissures. Ocelli borne on lateral plates. Each spinal cephalic plate with three protuberances: two posterior and one apical. Antennae 3-segmented, segment III (n = 1, 0.060 mm), approximately 1.3x longer than segments I (n = 1, 0.028 mm) and II (n = 1, 0.019 mm) combined. Segment III with a subapical primary rhinarium with a few adjacent accessory rhinaria. Processus terminalis with 3 stout setae. Rostrum reaching past mid coxae, with ultimate segment as long (n = 1, 0.062 mm) as 0.7x the width of segment III at its midpoint (n = 1, 0.080 mm).

Coxae and femorotrochanters, and tibiae smooth, distitarsi weakly imbricated. Wax glands with approximately 20–40 loosely packed facets antero-lateral to all coxae. Hind femorotrochanter length: n = 1, 0.096 mm.

Pronotum with protuberant plates on the four corners of each spinal plate. Meso- and metanotum and abdominal segments I–IV with separate lateral, pleural, and spinal wax plates, each borne on a large protuberance. Abdominal segments V–VIII with only lateral plates with the protuberance becoming less pronounced and less sclerotized posteriorly. Abdominal segment IX with a lightly sclerotized transversely extended post-anal plate with a pair of long acuminate setae. Very lightly sclerotized sternites with wax glands with 4–12 loosely packed facets and 3–4 setae mesad to the spiracles on abdominal segments IV–VI. Acuminate setae abundant ventrally on segment VIII and dorsally on segment IX, and in a single spinal pair on each of the other abdominal segments. Ovipositor with length of gonapophyses (n = 1, 0.125 mm) 1.2x width across apodemes (n = 1, 0.108 mm).

Hosts and Distribution. Abies densa in Bhutan (Bumthang) ( Fig. 7 ).

Remarks. This species was collected from Abies densa in densely congregated colonies on the bark of the main stem and on the underside of lateral branches on twigs. On the twigs, the stylets were inserted mostly into the bark, and occasionally into the base of needles.

We tentatively place A. (D.) densae in Dreyfusia because it is sister to A. (D.) knucheli in the molecular phylogeny ( Fig. 1 ). It has some morphological similarities to A. (D.) pindrowi, and both A. (D.). pindrowi and A. (D.) densae have morphological similarities to A. (Ap.) pectinatae , which with its two subspecies, is the only member of Aphrastasia Börner, 1909. Adelges (D.). pindrowi was placed in Dreyfusia by Havill & Foottit (2007) and Favret et al. (2015b). However, Yaseen & Ghani (1971) remarked that A. (D.) pindrowi closely resembles Adelges (Aphrastasia) pectinatae ishiharai ( Inouye, 1936) , and Blackman & Eastop (2024) also remarked that A. (D.) pindrowi is “in the pectinatae group.” It might be appropriate to place A. (D.). pindrowi and A. (D.) densae in Aphrastasia; however A. (D.) densae is not sister to A. (Ap.) pectinatae in our molecular phylogeny. A more detailed morphological analysis of the adelgid species feeding on Abies , and a more robust phylogeny of the family could help to resolve a more informative delimitation of Aphrastasia.

It is possible that either A. (D.) densae or A. (G.) glandulae is the same as what Schmutzenhofer (1985) recorded as “ Chermes abietis-piceae ” on Abies densa at Thumsingla (= Phrumsengla). In our survey, both A. (D.) densae and A. (G.) glandulae were collected from Abies densa within 16 km of this locality. Chermes abietispiceae was originally described from northern India, alternating between Picea smithiana and Abies spectabilis ( Stebbing 1903a, b). It was later renamed Chermes himalayensis by Stebbing (1910) and given a more detailed description, but this name is an unavailable synonym of the earlier name. Chermes abietispiceae is currently considered a nomen dubium ( Favret 2024) because neither of Stebbing’s descriptions provide enough information about the appearance and arrangement of the wax glands to confirm its identity ( Schneider-Orelli & Schneider 1954). Our sample of A. (D.) densae was collected from the stem, not from the needles as described by Schmutzenhofer (1985), who observed their feeding causing a downward twisting of the needles. However, it is possible that, similarly to A. (D.) nordmannianae ( Pschorn-Walcher & Zwölfer 1958) , A. (D.) densae includes progredientes that feed on the needles that we did not sample. Ghani & Rao (1966) also speculated that A. (D.) knucheli could be the same as Chermes abietispiceae . Additional sampling in the region could resolve this.

Figures

FIGURE 1. Phylogeny of Adelgidae reconstructed using mitochondrial COI and cytb, and nuclear EF1α DNA sequence data. The topology shown is from maximum likelihood analysis with IQ-TREE. Specimen data is shown in Table 1. The new species are highlighted in red. For species with multiple specimens, the country of origin and sometimes the host plant are shown in square brackets to indicate different sources. SH-aLRT and ultrafast bootstrap support from the maximum likelihood analysis, followed by posterior probability from the Bayesian analysis are shown for each clade.

FIGURE 6. Adelges densae.A—C.Exules: first instar (paratype, USNM) (A), late instar (paratype, USNM) (B), adult (holotype, USNM) (C).

FIGURE 7. Map of Bhutan showing collection locations for Adelges (Dreyfusia) densae.