Dentifibula viburni Felt

Gagné, Raymond J. & Bertone, Matthew A., 2022, Redescription of Dentifibula viburni (Felt) (Diptera: Cecidomyiidae) and review of the genus, Zootaxa 5175 (5), pp. 583-592 : 584-589

Dentifibula viburni Felt

Figs 1–9 , 12–15 .

Contarinia viburni Felt 1907: 36 ; Felt 1908: 389 ( Dentifibula ); Felt 1918: 130 (redescription).

Contarinia caryae Felt 1907: 36 ; Felt 1908: 389 ( Dentifibula ); Felt 1918: 130 (redescription); Gagné 1973b: 869 (junior synonym of D. viburni ).

Dentifibula cocci Felt 1908 b: 389 ; Felt 1918: 130 (redescription); Gagné 1973b: 869 (junior synonym of D. viburni ).

Description. Adult. Color in life ( Fig. 2 ): Yellow with black antennae, black wing marks at tip of wing, center of wing immediately posterior to R5, at junction of M 4 and CuA and posterior to base of Cu, and black bands on legs.

Head ( Fig. 5 ): Eyes large, restricting postocciput, all facets closely contiguous, circular to hexagonoid. Occipital protuberance at least twice as long as wide, not reaching eye height because of large extent of eyes. Antenna: scape with 2-3 ventral and 1 lateral setae; pedicel with several lateral and medial setae; with 12 flagellomeres, first and second connate; male flagellomeres ( Fig. 3 ) binodal, both nodes spheroid, each with one circumfilum, internode and neck nearly as long as node, circumfilar loops comparable in length, loops reaching next distal node; female flagellomeres ( Fig. 4 ) cylindrical, circumfila closely appressed except for bowed loops at nodal apex, node and neck of third flagellomere subequal in length. Frons with 4–6 setae per side, without scales. Labella hemispheroid with several uniform, slightly thickened setae. Palpus 4-segmented, first segment short-spheroid, nearly hidden, remaining segments ovoid, each segment with several scattered, pointed setae of uniform length, without scales.

Thorax: Wing ( Fig. 2 ): length: male, 1.1–1.3 mm (n = 10); female, 1.3–1.5 mm (n = 10); R 5 slightly curved, joining C at wing apex; Rs evanescent; M 4 and CuA forming a fork. Scutum with 4 longitudinal groups of sparse setae mixed with scales. Scutellum with 3–4 setae on each side. Anepimeron with 3-4 setae, remaining pleura bare. Legs: claws untoothed, strongly curved beyond midlength; empodia nearly as long as claws; pulvilli diminutive.

Male abdomen. Tergites first through seventh with single row of posterior setae, a few lateral setae, anterior pair of trichoid sensilla and elsewhere with widely scattered scales; eighth tergite membranous, with no posterior setae and pair of anterior trichoid sensilla. Sternites second through sixth with single row of sparse posterior setae, several lateral and medial setae and scales near midlength, and anterior pair of closely approximated trichoid sensilla; seventh sternite similar except vestiture at midlength closely approaching posterior row of setae; eighth sternite with 2 well-separated trichoid sensilla, with sparse posterior row of long setae and a few shorter setae and scales. Terminalia ( Figs 6–8 ): cerci broadly rounded apically, each with three setae along distal edge; hypoproct broader than each cercus, low-convex apically, with 6 distal setae of approximately equal length, both surfaces uniformly microtrichose; aedeagus cylindrical, slightly elbowed dorsally near basal third, nearly as long as gonocoxite, with oval, dorsoapical opening near rounded apex and 4 apicolateral, hairless sensoria; gonocoxite broadly cylindrical, tapering abruptly beyond insertion of gonostylus into conical, posteromesally-directed lobe, apex with 2-3 setae no longer than breadth of lobe tip and without the single, long sensory peg found in some congeners (Figs 10–11); gonostylus sleek, cylindrical, narrowest near ¾ length, with 2 setae along length and 2 adjacent to solid tooth, any microtrichia not apparent.

Female abdomen. Tergites first through seventh as for male but lateral setae and covering scales more numerous; eighth tergite membranous with anterior pair of trichoid sensilla and a few short setae on posterior margin. Sternites second through seventh as for male but setae and scales at midlength more numerous and not prominently divided into separate groups; eighth sternite membranous, without vestiture except for widely separated anterior pair of trichoid sensilla. Ovipositor ( Fig. 9 ) short, protrusible part not much longer than seventh tergite, bare dorsally and laterally, with mixed long and short setae ventrally; cerci ovoid, bilaterally flattened, lateral surface with widely spaced setae, medial surface with scattered short setae and dense apicoventral group of more than 50 short setae, these setae slightly longer than width of their sockets; hypoproct broadly rounded apically, with 2 distal setae.

Pupa ( Fig. 15 ). Exuviae hyaline. Vertex bearing two papillae on each side, one with long seta, the other without. Antennal bases low-conic anteriorly. Face smooth, frons with papilla on each side, with seta, face with a triplet of papillae anteriad of each palpal base, one without seta, its base larger than those of other two, which each bear minute seta. Prothoracic spiracles elongate, cylindrical, tracheae reaching to apex. Abdominal spiracles on first segment not raised above surface, on segments second through sixth several times longer than basal width, tapered and stiff, on segments seventh and eighth barely longer than basal width. Abdominal first segment with short spicules only on pleura, remainder smooth; segments second through eighth covered with short spicules of uniform length except anterior third of tergum mostly covered with larger, spinose spicules; terminal segment covered with short spicules.

Larval third instar. ( Figs 12–14 ). Length, 1.5-1.8 mm (n = 10). Head broad, rounded apically, apodemes longer than head capsule, antennae as long as head capsule, slightly tapered from base, rounded apically. Spatula present, with two rounded anterior lobes and long shaft with wavy edges. Dorsal integument smooth, without spicules; ventral integument mainly smooth except for pseudopods, 2 each on meso- and metathorax and 3 each on first through seventh abdominal segments, those segments also with horizontal anteroventral rows of spicules, 3 rows on mesothorax, the number gradually increasing through the seventh abdominal, the eighth with several rows but situated posteriorly, and terminal segment with 3 low, smooth convexities surrounded by spicules. Anus dorsal. Papillae: collar segment with 2 dorsals and 2 ventrals, all without setae; 6 setose dorsals on each thoracic and first through seventh abdominal segments, first and sixth setae of each row longest, third and fourth shorter, about as long as pleural papillae, and second and fifth setae quite short, about one-fourth as long as middle pair, and eighth abdominal segment with 2 dorsals, as long as longest pair of other segments; 6 terminals bearing long setae of equal length with rounded apices, as long as longest pair of other segments; two setose pleurals on each side of all thoracic and abdominal segments except terminal; 2 sternals without setae on prothorax and four on eighth abdominal segment, all without setae, all sternals elsewhere undetectable, apparently lost; laterals in two usually closely contiguous triplets on each side of midline of thoracic segments, one of each triplet with long seta, remainder without, the setose member of triplet may be separate from remaining two ( Fig. 12 ); and single setose ventral on each side on thoracic and first through seventh abdominal segments.

Material examined. Types of names under this taxon: holotype male of D. viburni, Albany , New York, swept from Viburnum acerifolium L. ( Adoxaceae ), VI-11-1906, deposited in NYSM; holotype male of D. caryae, Albany , New York, swept from Carya sp. (Juglandaceae) , VI-19-1906, deposited in NYSM; holotype male of D. cocci , Illinois, reared V-1-1897 from Diaspidiotus uvae (Comstock) (Diaspididae) , (as Aspidiotus uvae ), deposited in USNM.

Other specimens (all in USNM): USA: 3 larvae, 2 males, female, Gainesville, Florida, reared from Pseudaulacaspis pentagona (Targioni-Tozzetti) (Diaspididae) on Morus rubra L. ( Moraceae ), XI-15-1973, F. Collins; male, Hancock Co., Maine, VIII-21-1981, R. J. Gagné; male, Beltsville , Maryland, V-17 to 21-1970, R. W. Carlson; male, Silver Spring , Maryland, VII-19-1981, R. J. Gagné; Maryland: 3 males, female, Rockville , Maryland, from Pseudaulacaspis prunicola (Maskell) (Diaspididae) , IX-2-1981, T. Rivnay ; 3 males 2 females, Oxon Hill , Maryland, reared IX-2-1981 from P. pentagona ; 8 males, four females, 2 pupae and 7 larvae, Asheville , North Carolina, reared/taken IV-22-2022 from P. prunicola , infesting Prunus laurocerasus L. collected III-24-2022, M.A. Bertone; 2 males, 3 females, Pisa , Italy, reared from Targiona vitis (Signoret) (Diaspididae) , A. Lucchi; and 1 male, Sweden, Smǻland , Nybro , Bäckebo , Grytsjön Nature Reserve , old-growth aspen forest on boulder terrain, VII-2 to VII-12-2005, Malaise trap, Swedish Malaise Trap Project .

Remarks. Felt (1907, 1908, 1918) described D. viburni under three names, separating them on the basis of superficial characters that included relative proportions of antennae and legs. He also used purported color differences due to bodily sclerotization but not the definite marks due to vestiture that occur on the specimens prior to mounting. This species is distinct among its congeners for the lack of a sensory peg at the apex of the gonocoxite, the tooth of the gonostylus is not significantly wider than the shaft, and the aedeagus is only slightly shorter than the gonocoxite. As the only Dentifibula in the Western Hemisphere and a geographic range that includes Italy and Sweden, it is possible the species was transported to North America on plants infested with a diaspidid host at some point following European colonization.

Distribution. This species is widespread in eastern USA and was found once each in Italy and Sweden. It has been reared from four species of Diaspididae : Diaspidiotus uvae , Pseudaulacaspis pentagona , Pseudaulacaspis prunicola , and Targiona vitis .

Behavior. Larvae from the Asheville, North Carolina, series were found beneath the coverings (tests) of its diaspidid host. Although scale populations in this instance were high, there remained very few live scale insects, and those were mostly being fed upon by D. viburni ( Fig. 1 ). Larvae were found to be covered entirely by the scale tests, and full-grown larvae formed their cocoons under the tests. A few scales were parasitized also by chalcidoid wasps.

Collins & Whitcomb (1975) gave a further account of this species on white peach scale, P. pentagona , collected from several plants in northern Florida: “The female would walk about on a stem, dragging the tip of her abdomen, until a crevice was found where she would lay 1- 4 eggs in 1 to 2 min. The hollow beneath an uplifted scale armor or a notch in the bark were typical oviposition sites though eggs were also observed on smooth bark away from scales. Larvae were seen attached to the female scale body, on the dorsal or ventral side or adjacent to it, with mouthparts hooked into the scale. On some branches as many as 3 or 4 larvae were attached to the body of a female scale. The larva would construct a thin, white, papery [cocoon] and expel a single, brown, spherical fecal pellet prior to pupation. The [pupae] were found beneath scale shields which were either cleaned out or still contained a dead, shriveled scale body.”

Figures

FIGURES 1–2. 1, Third instar and cocoon (pupa departed) of Dentifibula viburni among scales Pseudaulacaspis prunicola (Maskell). 2, Male of Dentifibula viburni. Photos by M. Bertone.

FIGURES 3–9. Dentifibula viburni. 3, Male fourth flagellomere (ventral). 4, Female fourth flagellomere (ventral). 5, Head with detail of palpus (frontal). 6, Male terminalia (dorsal). 7, Same (ventral). 8, Same (sagittal). 9, Terminus of ovipositor (lateroventral). Figures 10–11, Visible details of terminalia of uncleared types. 10, Dentifibula ceylanica. 11, Dentifibula obusilobae.

FIGURES 12–15. Dentifibula viburni. 12, Third instar, anterior segments (ventrolateral). 13, Same, first thoracic segment (dorsolateral). 14, Same, terminal segment (ventral). 15, Pupa, anterior segments (ventral).