Disholcaspis prehensa Weld, 1957

Cooke-Mcewen, Crystal & Gates, Michael, 2020, Contributions to Disholcaspis Dalla Torre And Kieffer (Hymenoptera: Cynipidae: Cynipini), Zootaxa 4859 (3), pp. 355-382 : 368-370

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Disholcaspis prehensa Weld, 1957


Disholcaspis prehensa Weld, 1957   , sexual generation

Material examined: Specimens with USNM barcode labels USNMENT00961656 (♀), USNMENT00961763 (♂), USNMENT00961924 (♀), USNMENT00961568 (♂), USNMENT00961761 (♂), USNMENT00961702 (♀), and USNMENT00961465 (♂) from the earlier molecular analysis   .

Diagnosis: This sexual generation is diagnosed by the following combination of traits unique to this Disholcaspis   sexual generation compared to all others currently known: body dark brown, F1 shorter than scape+pedicel, F2 subequal to F1, wing veins brown, radial cell 3.9x as long as wide, extended portion of ventral hypopygial spine parallel near base then tapering to tip, and extended portion of ventral hypopygial spine 1.1–1.2x as long as broad basally.

Sexual female ( Fig. 21–30 View FIGURES 21–26 View FIGURES 27–30 ): Total body length 2.2–2.4mm. Color. Antennae and mouth palps light brown to brown, sometimes getting gradually darker towards apex; head, mesosoma, and coxae dark brown to black; legs light brown to golden; metasoma dark brown; wings hyaline with dark brown veins.

Head ( Fig. 22–24 View FIGURES 21–26 ). Anteriorly 1.1x as broad as high, finely coriaceous with malar space more delicately coriaceous; rounded in anterior view with ocelli raised; lower face with sparse setae. Gena not broadened behind compound eye in anterior view; lateral width of the gena 0.35x as wide as the compound eye height. Compound eye 0.6x as high as frontal head height, transfacial line 1.1x as long as compound eye height; length of malar space 0.6x height of compound eye; compound eyes slightly converging ventrally. LOL 0.99–1.4x the length of the lateral ocellus; OOL 1.5–1.8x length of lateral ocellus; POL 1.3–1.5x as long as OOL and 2.2–2.6x as long as length of lateral ocellus. Diameter of torulus subequal to distance between them; distance between torulus and compound eye margin 1.2x the diameter of torulus. Clypeus rectangular, 1.3x as broad as high, ventral margin convex; tentorial pits present; clypeo-pleurostomal line indistinct; epistomal sulcus broad, shallow, smooth, and bare. Occiput rounded and without carina. Labial palpus 3–segmented, maxillary palpus 4–segmented. Antennae 14–segmented; pedicel as long as broad; antennal segment length ratio 16:7:21:19:18:17:14:14:11:12:10:11:8:14; placoid sensilla present on F3–12.

Mesosoma ( Fig. 25–29 View FIGURES 21–26 View FIGURES 27–30 ). Laterally 1.2x as long as high. Pronotum with delicate longitudinal striations medially, setose dorsally, ventrally with sparse setae, margin along mesopleuron with fine striations; impressed along propleuron. Propleuron striate along margins, flat medially. Mesoscutum delicately coriaceous around notauli and along anterior and anterolateral margins, sometimes very delicately coriaceous between notauli and on anterior third of mesoscutum; 1.1x as wide as long. Notauli present in posterior 2/3 fading to coriaceous texture anteriorly, incomplete and converging posteriorly; anterior parallel lines either not visible or only visible when the anterior third of mesoscutum is delicately coriaceous; parapsidal broad and smooth, extending just over 1/3 length of mesoscutum; median mesoscutal line absent; setae along notauli and lateral margin of mesoscutum. Mesoscutellum slightly longer than broad, rugose, overhanging metanotum; scutellar foveae indistinct with rugose texture intruding. Mesopleuron mostly smooth with several indistinct transverse striations, setae near mesocoxa foramen; mesopleural triangle setose and with transverse striations; acetabular carina distinct. Dorsoaxillar area smooth but setose, slightly convex; axillar carina with longitudinal striae; axillula setose and delicately coriaceous; subaxillular bar smooth; metapleu- ral sulcus reaching mesopleuron just over half its height. Metascutellum delicately rugose; metanotal trough smooth and with setae; ventral impressed rim smooth. Lateral propodeal carinae bent outward at the middle sometimes nearly merging dorsally forming a ring, medial propodeal area with varying numbers of carinae extending from the lateral propodeal carinae towards the nucha; lateral propodeal area setose; nucha short with longitudinal carinae. Forewing extending beyond apex of metasoma; radial cell 3.9x as long as wide; M, Rs+M, and Cu1a barely visible; Rs curved slightly, nearly reaching wing margin; areolet closed and indistinct. Tarsal claws with basal lobe.

Metasoma. Tergum two with setae laterally, following four terga without setae; all terga smooth and shiny. Extended portion of ventral hypopygial spine ( Fig. 30 View FIGURES 27–30 ) parallel basally then tapering to tip, extended portion 1.1–1.2x as long as broad basally, with subapical setae reaching beyond spine apex.

Male ( Fig. 31–34 View FIGURES 31–35 ): Similar to females in coloration and size; however, antennae generally a brown to dark brown, antennae 15-segmented, basal half of femora are brown, and propodeum with lateral propodeal carinae not nearly merging dorsally.

Gall ( Fig. 35 View FIGURES 31–35 ): Length 2.2–3.5mm, buff to light brown colored, oblong grain-shaped, bluntly or sharply pointed, thin walled, and glabrous. Arising from the buds at the base of new leaves and flowers when they flush in the spring. Emergence holes are rough edged and near the apex.

Host plant remarks: Quercus dumosa   is the host plant listed in the original description of D. prehensa ( Weld 1957)   . However, the name Q. dumosa   has been applied to almost all species of scrub oak in central and southern California. Asexual generation D. prehensa   have also been photo-documented (Gross J. 2007 and 2012) and reared from Q. berberidifolia   (listed as host for specimen D_prehensa_Dispre3). The host plant voucher for the sexual generation specimens USNMENT00961761, USNMENT00961924, and USNMENT00961763 is deposited at MARY and identified as Q. berberidifolia   . This shows that the sexual generation of D. prehensa   is found on the same host species as the asexual generation. There is no host plant identification or voucher specimen corresponding to USN- MENT00961702, USNMENT00961656, USNMENT00961568 and USNMENT00961465.


Smithsonian Institution, National Museum of Natural History