Adelges (Cassiadelges) coccipus Havill & Brunet, 2025

Adelges (Cassiadelges) coccipus Havill & Brunet , sp. nov.

( Fig. 2A–J View FIGURE 2 )

Etymology. A noun in apposition stemming from the Greek ΚΌΚΚΟς meaning “berry” and ΠΟΎς, meaning “foot,” in reference to the round vestigial legs. Also, in reference to the developmental similarity to many scale insects (Coccomorpha).

Type material. HOLOTYPE: 1 adult exulis, BHUTAN, Bumthang, Shingnyer , lat. 27.4595, long. 90.8690, 5-IV-2022, on Larix griffithii, Kaka Tshering ( USNM) . PARATYPES: 1 first instar progrediens, same data ( CNC#5338333-15 View Materials ) . 1 adult exulis, same data ( CNC#5338333-8 View Materials ) . 1 first instar progrediens, same data ( USNM) . 1 adult exulis, same data ( YPM # ENT594747 About YPM ) . 1 adult exulis, BHUTAN, Mongar, Sengor , lat. 27.3642, long. 91.0328, 27-III-2022, on Larix griffithii, Namgay Sacha , Kaka Tshering ( CNC#5338328-4 View Materials ) . 1 nymph exulis, same data ( NBC) . 1 second instar exulis, same data ( USNM) . 1 first instar sistens, BHUTAN, Mongar, Sengor , lat. 27.3652, long. 91.0346, 27-III-2022, on Larix griffithii, Namgay Sacha , Kaka Tshering ( CNC#5338325-12 View Materials ) . 1 second instar exulis, same data ( YPM # ENT594677 About YPM ) . 1 adult exulis, 1 first instar sistens, same data ( NBC) . 1 first instar progrediens, BHUTAN, Mongar, Sengor , lat. 27.3683, long. 91.0127, 7-IV-2022, on Larix griffithii, Kaka Tshering ( CNC#5338330-10 View Materials ) . 1 first instar progrediens, same data ( NBC) . 1 first instar sistens, same data ( USNM) . 1 first instar sistens, same data ( YPM # ENT594732 About YPM ) . 1 first instar progrediens, same data ( YPM # ENT594731 About YPM ) . 1 adult exulis, BHUTAN, Bumthang, Tangsibi , lat. 27.4891, long. 90.8625, 6-IV-2022, on Larix griffithii, Kaka Tshering ( CNC#5338331-5 View Materials ) .

Additional specimens examined. BHUTAN: Bumthang: Shingyner: 1 egg, 4 first instar progredientes, 12 adult exules ( CNC), 1 first instar progrediens, 2 adult exules ( NBC), 1 first instar progrediens, 2 adult exules ( USNM), 2 first instar progredientes, 2 adult exules ( YPM), lat. 27.4595, long. 90.8690, 5- IV- 2022, on Larix griffithii, Kaka Tshering. Mongar: Sengor: 1 late instar nymph exulis, 19 adult exules ( CNC), 3 adult exules ( NBC), 1 late instar nymph exulis, 5 adult exules ( USNM), 3 first instar sistentes, 6 late instar nymph exules, 26 adult exules ( YPM), lat. 27.3642, long. 91.0328, 27-III-2022, on Larix griffithii, Namgay Sacha, Kaka Tshering. 1 first instar sistens, 2 late instar nymph exules, 24 adult exules ( CNC), 1 first instar sistens, 1 late instar nymph exulis ( NBC), 4 first instar sistentes, 6 late instar nymph exules, 37 adult exules ( USNM), 14 first instar sistentes, 2 first instar sistens exuviae, 11 late instar nymph exules, 6 adult exules ( YPM), lat. 27.3652, long. 91.0346, 27-III-2022, on Larix griffithii, Namgay Sacha, Kaka Tshering. 3 eggs, 5 first instar progredientes, 1 late instar nymph exulis, 6 adult exules ( CNC), 3 first instar progredientes ( USNM), 19 first instar progredientes, 9 adult exules ( YPM), lat. 27.3683, long. 91.0127, 7- IV- 2022, on Larix griffithii, Kaka Tshering. Bumthang: Tangsibi: 1 egg, 3 first instar progredientes, 1 late instar nymph exulis, 4 adult exules ( CNC), 1 adult exulis ( NBC), 3 first instar progredientes, 1 late instar nymph exulis, 3 adult exules ( USNM), 1 first instar progrediens, 9 adult exules ( YPM), lat. 27.4891, long. 90.8625, 6- IV- 2022, on Larix griffithii, Kaka Tshering.

Diagnosis. Adelges (Ca.) coccipus lacks developed legs in all exulis stages after the first instar. The general wax gland structure in the neosistens is similar to Sacchiphantes and Cholodkovskya in that the facets are arranged in a rosette pattern around a central seta, but they are more tightly packed than in the other subgenera. The abdominal spiracles in adult exules are very small and without sclerotization making them difficult to see except at high magnification. The strongly sclerotized cephaloprothoracic shield resembles many Pineus species, but having five pairs of abdominal spiracles and molecular phylogeny places this species definitively within Adelges ( Fig. 1 View FIGURE 1 ).

Description. Neosistens ( Fig. 2A View FIGURE 2 ). Body length: n = 7, 0.359 –0.451 (0.406) mm. Body width: n = 6, 0.202 –0.293 (0.260) mm. Dorsal wax glands generally on lightly sclerotized plates with 3–6 facets, often triangular, sometimes rhomboidal to circular, with a granular appearance, arranged in tightly packed rosettes around a central seta.

Head and pronotum with lightly sclerotized dorsal plates, separated from each other and along mid-line by narrow sutures. Each cephalic dorsal plate with five or six wax glands, one apical often folded ventrally in slide-mounted specimens, two anterior arranged transversely, two mesad to ocelli arranged longitudinally, sometimes one postero-spinal. Generally, 2–7 facets per cephalic gland. Postero-spinal gland, when present, with fewer facets than the others. The largest wax gland facets on head approximately half the diameter of ocellus. Antennae 3-segmented, segment III imbricated, with length [n = 8, 0.041 –0.052 (0.045) mm] 3.1x its width at midpoint [n = 8, 0.013 –0.016 (0.015) mm], and approximately 1.4x longer than segments I [n = 8, 0.015 –0.026 (0.020) mm] and II [n = 8, 0.016 – 0.024 (0.020) mm] combined. Two primary rhinaria on antennal segment III, one subapical and one approximately ½ the segment length from the apex, each with a small thumb-like projection. A few accessory rhinaria adjacent to the subapical primary rhinarium. Processus terminalis with five setae, the apical seta length [n = 6, 0.046 –0.056 (0.051) mm] approximately 3–4x longer than the rest. Rostrum reaching past hind coxae, with ultimate segment length [n = 7, 0.033 –0.040 (0.037) mm] subequal to width of segment III at midpoint [n = 7, 0.036 –0.045 (0.042) mm]. Stylet length: n = 6, 1.314 –1.728 (1.579) mm, approximately 3.9x body length.

Coxae, femorotrochanters, and tibiae smooth, second tarsal segments weakly imbricated. Pair of long dorso-subapical setae on foreleg. Pairs of subequal dorso-subapical setae on mid- and hindlegs. Wax glands anterior to coxae lacking. Hind femorotrochanter length: n = 7, 0.045 –0.057 (0.049) mm.

Pronotum with one antero-lateral and sometimes one postero-lateral wax gland on each plate. Mesonotum with one lateral wax gland. Metanotum with one lateral wax gland, usually with fewer facets than on pro- and mesonotum, sometimes lacking. Raised ventral spiracles on meso- and metanotum bearing facets on basal surface. Abdominal wax glands lacking. Abdominal spiracles minute, hardly visible. Acuminate ventral setae in lateral, pleural, and spinal positions on abdominal segments I–VI, in lateral and spinal positions on abdominal segment VII, in a lateral position on abdominal segment VIII, and a pair of long setae on the apex of abdominal segment IX. Abdominal setae not always apparent.

Neoprogrediens ( Fig. 2B–C View FIGURE 2 ). Body length: n = 12, 0.415 –0.482 (0.451) mm. Body width 0.244 –0.295 (0.265) mm. Body lacking wax glands.

Head and pronotum with very lightly sclerotized plates, separated from each other and along mid-line by narrow sutures. Each dorsal cephalic plate with six setae, one postero-spinal, one postero-lateral, one antero-spinal, two antero-lateral, one apical. A pair of ventro-spinal setae between antennae. Antennae 3-segmented, segment III imbricated, length [n = 13, range 0.044 –0.062 (0.052) mm] approximately 3.1x its width at midpoint [n = 13, 0.014 –0.020 (0.017) mm], and subequal to segments I [n = 13, range 0.019 –0.030 (0.024) mm] and II [n = 13, range 0.022 –0.031 (0.026) 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. A few accessory rhinaria adjacent to the subapical primary rhinarium. Processus terminalis with five setae, the apical seta length [n = 12, 0.038 –0.051 (0.044) mm] approximately 3x longer than the rest. Rostrum reaching just anterior to hind coxae. Stylets short [n = 13, 0.411 –0.680 (0.477) mm], approximately 1.0x body length.

Coxae, femorotrochanters, and tibiae smooth, second tarsal segments imbricated. Pair of dorso-subapical setae on foreleg, one capitate seta approximately 2x longer than the other acuminate one. Pairs of subequal dorso-subapical setae of mid- and hindlegs. Wax glands anterior to coxae lacking. Hind femorotrochanter length: n = 13, 0.053 –0.065 (0.058) mm.

Prominent, raised ventral spiracles on the meso- and metanotum bearing facets on basal surface ( Fig. 2C View FIGURE 2 ). Abdominal spiracles not apparent. Acuminate ventral setae in lateral, pleural, and spinal positions on all thoracic segments and abdominal segments I–VI, in lateral and spinal positions on abdominal segment VII, in a lateral position on abdominal segment VIII, and a pair of long setae on the apex of abdominal segment IX.

Adult exulis ( Fig. 2F–J View FIGURE 2 ). Body length: n = 21, 0.631 –1.044 (0.802) mm. Body width: n = 21, 0.579 –0.877 (0.752) mm. Pronotum width: n = 21, 0.484 –0.698 (0.600) mm. Body shape transverse oval to nearly round. Dorsal wax glands generally with one to approximately 20 contiguous or nearly contiguous small round pores.

Head and prothorax strongly sclerotized on dorsal and ventral surfaces. Dorsal plates of head and pronotum completely fused into cephaloprothoracic shield with distinctly wrinkled surface.Anterior half of cephaloprothoracic shield bearing numerous small wax glands with usually less than 10 thick-walled, round to ovoid, tightly packed facets ( Fig. 2J View FIGURE 2 ). Wax glands on both dorsal and ventral surfaces of cephaloprothoracic shield. Wax glands less numerous (often absent), smaller, and with fewer facets on posterior half of cephaloprothoracic shield. The largest wax facets on the head approximately half the diameter of ocellus. Antennae greatly reduced, appearing as a narrow ridge with no apparent segmentation ( Fig. 2H View FIGURE 2 ). Rostrum with ultimate segment length [n = 13, 0.031 –0.042 (0.038) mm] approximately 0.7x width of segment III at midpoint [n = 13, 0.047 –0.059 (0.052) mm].

Vestigial legs present as slightly raised cuticular protrusions on pro-, meso-, and metanotum with clusters of approximately 8–15 setae ( Fig. 2G View FIGURE 2 ). Vestigial legs on meso-, and metanotum unsclerotized. Anterior base of vestigial legs with 0–5, usually 1–2, small wax glands with one to approximately 12 round facets.

Meso- and metanotum, and abdominal segments I–II usually with1–9 small lateral wax glands with approximately 1–20 facets each. Mesonotum with pleural wax glands, or an irregular transverse row of 0–4 small wax glands consisting of 2–8 facets. Prominent, strongly sclerotized and raised ventral spiracles on meso- and metanotum. Rarely, a single small lateral wax gland with a 1–14 minute facets on some of abdominal segments III–VII. Minute unsclerotized spiracles on abdominal segments II–VI ( Fig. 2I View FIGURE 2 ), often not apparent but sometimes recognizable if internal trachea leading to them are preserved in the specimen. Acuminate setae abundant on abdominal segment IX. Ovipositor short, with length of gonapophyses [n = 10, 0.029 –0.059 (0.043) mm] approximately 0.9x the width across apodemes [n = 10, 0.034 –0.061 (0.044) mm].

Host and Distribution. Larix griffithii in Bhutan (Mongar and Bumthang) ( Fig. 3 View FIGURE 3 ).

Remarks. Adelges (Ca.) coccipus feeds at the base of the buds and needle whorls, and on the bark on twigs of Larix griffithii . Similar to many other adelgid species, A. (Ca.) coccipus has morphologically dissimilar sistens and progrediens forms in the first instar, with sistentes having stronger sclerotization and longer rostral stylets (Havill & Foottit 2007). All but one of the first instars collected on March 27 were sistens forms, while all the first instars collected on April 5–7 were progrediens forms. The neosistentes on the earlier date were likely the remnants of the overwintering generation that had not developed because all of the specimens in our possession were damaged to some degree. The progredientes collected later were alive and abundant. This could indicate the presence of a longer generation of overwintering sistens individuals with an intervening series of short generations of progredientes individuals. We did not observe a dichotomy among the adults that would indicate morphologically distinct sistens and progrediens, nor did we collect sexupara adults into which a proportion of progrediens nymphs often develop in other species. In addition, their DNA sequences did not match any specimens on Picea , so there is no indication at this point that A. (Ca.) coccipus can complete a holocycle.

This is the first known legless species in the Aphidomorpha. The nymph illustrated in Fig. 2D–E View FIGURE 2 was confirmed as a second instar because it was found emerging from its first instar exuvium. This confirms that all but the first instar lacks legs and have reduced antennae ( Fig. 2E View FIGURE 2 ). We are not aware of any other completely legless species within Aphidomorpha, but some species, scattered throughout Aphididae have reduced leg structures. For example, Colopha hispanica Nieto Nafría & Mier Durante, 1987 ( Aphididae : Eriosomatinae ), some Quadrartus species ( Aphididae : Hormaphidinae ) ( Takahashi 1958; Sorin 2001), Mastopoda pteridis Oestlund, 1886 ( Aphidinae : Macrosiphini ), and Atarsos grindeliae Gillette, 1911 ( Aphidinae : Macrosiphini ) all have shortened legs with some segments missing or fused.

Being nested well into the Adelgidae , A. (Ca.) coccipus represents an independent evolution of the apodous trait commonly found in scale insects ( Hemiptera : Sternorrhyncha: Coccomorpha). In scale insects, legs can be entirely missing, or represented by a variety of reduced morphologies ( Gullan & Kosztarab 1997). The morphology of A. (Ca.) coccipus leg vestiges as clusters of setae is similar to some species of flat grass scales ( Hemiptera : Acleridae; McConnell 1953) and legless mealybugs ( Hemiptera : Pseudococcidae : Pseudococcinae: Serrolecanini; Hendricks & Kosztarab 1999).

The phylogeny ( Fig. 1 View FIGURE 1 ) places A. (Ca.) coccipus sister to an undescribed species from China that will be dealt with in a subsequent publication when more specimens are available for a full description. This other species has all of the features of Cassiadelges , but unlike A. (Ca.) coccipus , it has fully developed legs. Comparison between Adelges (Ca.) coccipus and A. (Ca.) nr. coccipus presents an exciting opportunity to examine the evolutionary development of insect limb formation from a new perspective.