Hamamelistes blackmani Dederich and von Dohlen, 2022

Dederich, Ashley E., Halbert, Susan E. & Von Dohlen, Carol D., 2022, Description of a new species of Hamamelistes forming galls on Fothergilla spp (Hamamelidaceae) and the generic limits of Hormaphidini (Sternorrhyncha Aphididae: Hormaphidinae), Zootaxa 5183 (1), pp. 203-219 : 205-210

Hamamelistes blackmani Dederich and von Dohlen , sp. nov.

The following descriptions are based on galls from F. milleri , and the aphids therein, collected at the Perdido River Wildlife Management Area , Baldwin County, Alabama, USA. Samples for slide mounts were collected on 7 August 2018 ; samples for gall measurements and life stages were collected on 23 July and 21 August 2019.

Gall. Galls are oblong and are formed on fruiting structures. At maturity, when alates emerge, galls are approximately 30-47 mm long and 7–13 mm wide. The color is medium brown with a roughened outer surface; the interior tissue is green ( Fig. 1 ).

Fundatrix (gall foundress) adult ( Fig. 3 ), described from 10 specimens. All measurements are presented in Table 2 . Color in life dark purple-brown, with light dusting of wax. Body shape nearly round (slightly oval). Head, thorax, and abdominal segment 1 are fused, with segments difficult to distinguish; eye a triommatidion. Antenna three-segmented (sometimes appearing four-segmented), with segments I and II nearly equal in length. Rostrum reaching approximately halfway between first and second coxae; ultimate rostral segment (URS) short and blunt; stylets approximately the same length as rostrum. Legs short; hindleg with two tarsal segments with distinct claws. Fore-tarsus slightly smaller than hind tarsus, with tarsal segments sometimes fused. Siphunculi absent. Anal plate bilobed; cauda knobbed.

First-instar nymph to be alate (emigrant) ( Fig. 4 ), described from 16 specimens.All measurements are presented in Table 3 . Body oblong, tergites with little-to-no sclerotization; head fused with prothorax.Antenna four-segmented, with segments III and IV approximately equal in length. Rostrum reaching between mid and hind coxae; URS short and blunt; stylets approximately the same length as rostrum. Setae on segment I and II of hind tarsus acuminate; segment II bears one medial pair and one apical pair of setae. Abdomen with siphuncular pores, not sclerotized.

Second-instar nymph to be alate (emigrant), described from 2 specimens. All measurements are presented in Table 3 . Other characteristics are as in the first-instar to be alate.

Adult gallicola (alate emigrant) from the gall ( Fig. 5 ) described from 12 specimens. All measurements are presented in Table 4 . Color in life dark purple-brown, wings hyaline. Cephalic tubercle at vertex between antennae. Antenna five-segmented, with segments III-V bearing annular secondary rhinaria; processus terminalis and its apical setae short; third antennal segment shorter than fore tibia. Rostrum reaching below first coxae; URS short and blunt; stylets approximately the same length as rostrum. Tarsi two-segmented, with one pair of claws; hind tarsal segment I with one pair of basal acuminate setae; hind tarsal segment II with three pairs of setae. Forewing with medius unbranched and cubitus once branched with bases connected; common stalk approximately one-quarter the length of Cu1b. Hindwing with two oblique veins, separated. Siphunculi ring-like, slightly raised at center. Abdominal tergites membranous. Cauda knobbed; anal plate bilobed.

First-instar exalate nymph (offspring of alate emigrant) ( Fig. 6 ), described from 1 specimen. All measurements are presented in Table 3 . Body oblong, tergites with little-to-no sclerotization; head fused with prothorax. Antenna four-segmented, with segment III slightly longer than IV. Rostrum reaching between mid and hind coxae; stylets slightly longer than rostrum; other characteristics as in first-instar to be alate.

Hostplants and biology

The only known hosts are Fothergilla milleri and F. gardenii . Ha. blackmani sp. nov. induces galls on fruiting structures of these Fothergilla species, preventing seed development. The galls have been observed or collected on diploid F. milleri in Florida and Alabama, USA, and on tetraploid Fothergilla gardenii in North Carolina, USA (R. Miller, M. Jenkins, C. Hale, pers. comm.) (the taxonomy of Fothergilla has been updated recently ( Haynes et al. 2020)). Samples collected in late July contained fundatrices and primarily first- and second-instar nymphs; samples in late August contained nymphs of first-to-fourth instars and adult alates. Alate emigrants emerge through exit holes at either end of the gall; the galls are empty by early September. The typical life cycle of Hamamelistes spp. is host-alternating: alates maturing in Hamamelis pouch galls (virginoparae) migrate in late summer to Betula and produce “coccidiform” nymphs (oval, flattened, with a characteristic marginal ring of bead-like wax glands); these overwinter on twigs and induce pseudogalls on Betula the following spring. Alates (sexuparae) emerging from pseudogalls fly back to Hamamelis in late spring and produce sexual females and males. These mate and lay overwintering eggs, which hatch in spring into foundresses (fundatrices) that induce pouch galls on Hamamelis (see Aoki et al. 2001; von Dohlen 1991 for more details of the life cycle).

The complete life cycle of Ha. blackmani is not confirmed, but unlike other Hamamelistes species, is predicted to be monoecious. The morphology of the exalate nymph most closely resembles nymphs of the Hamamelistes sexual generation: it has sparsely patterned marginal wax plates and short stylets. In host-alternating species, coccidiform nymphs that feed on twigs of the birch secondary host are densely surrounded by a marginal ring of wax plates and have much longer stylets than sexual forms (S. Aoki, personal communication).

1 Morphometric data are shown as ranges and means; meristic data are given as ranges only. Measurements are in mm.

Discrimination from related species

Ha. blackmani sp. nov. is distinguished from North American Hormaphis and Hamamelistes spp. by the elongate gall formed on fruiting terminals of Fothergilla spp. It is further distinguished from Hormaphis in North America by the number of antennal segments in alates (five), which is three in Ho. cornu (Shimer) and Ho. hamamelidis . Alate forms are discriminated from Ha. spinosus by the presence of siphunculi (absent in Ha. spinosus ) and the number of secondary rhinaria on the third antennal segment ( Table 5 ). For comparison to alates of Japanese species, see Table 5 .

Etymology

The specific epithet of the new species is named as a tribute to the late aphidologist, Roger Blackman.

Type material

Holotype. One alate adult (emigrant) singly mounted on a slide, labeled “ USA: Alabama, Baldwin Co.; 7-viii-2018; Ron Miller, coll.; ex Fothergilla milleri ; FSCA # E2018-4222 .” ( FSCA)

Paratypes. 10 slides each containing one adult fundatrix, 16 slides each with one first-instar nymph to be alate, two slides each with one second-instar nymph to be alate, 11 slides each with one adult emigrant alate, one slide with one first-instar exalate nymph. All have the same label data as the holotype. ( FSCA) .

Figures

FIGURE 1. Galls of Hamamelistes blackmani sp. n. on Fothergilla. A. Fothergilla gardenii plant with multiple galls (fawnbrown, oblong, displacing seed pods) (Carteret Co., North Carolina USA). B - C, galls on F. milleri, Baldwin Co., Alabama USA. B. Cut gall showing aphids in the interior. C. Close-up of gall interior, with fundatrix (large oval), adult alate, and nymphs of several instars. Photo credits: Ron Miller (A, B); Lyle Buss (C).

FIGURE 3. Hamamelistes blackmani sp. n., adult fundatrix. A. Whole body. B. Antenna. C. Genital plate. D. Anal plate. E. Cauda.

FIGURE 4. Hamamelistes blackmani sp. n., first-instar nymph to be alate. A. Whole body. B. Antenna with sensory pegs.

FIGURE 5. Hamamelistes blackmani sp. n., adult alate. A. Right body. B. Antenna. C. Genital plate. D. Anal plate. E. Cauda.

FIGURE 6. Hamamelistes blackmani sp. n., first-instar exalate nymph (offspring of alate from gall). A. Whole body. B. Anterior region showing bead-like marginal wax plates.