Trissolcus utahensis (Ashmead), 1893

Ganjisaffar, Fatemeh, Talamas, Elijah J., Bon, Marie Claude & Perring, Thomas M., 2020, First report and integrated analysis of two native Trissolcus species utilizing Bagrada hilaris eggs in California, Journal of Hymenoptera Research 80, pp. 49-70 : 49

Trissolcus utahensis (Ashmead)

Remarks.

The concept of Trissolcus utahensis was most recently treated in a revisionary context by Johnson (1985). This treatment separated T. utahensis from T. cosmopeplae based on the length of the anteroventral extension of the metapleuron, the absence of a genal carina, the shape of the gena in lateral view, and if notauli could be distinguished from the surface sculpture of the posterior mesoscutum. These characters were used again in the key to Nearctic Trissolcus by Talamas et al. (2015), with the addition of the form of the mesoscutal humeral sulcus, which was treated as variable within T. cosmopeplae . Talamas et al. (2015) also treated the anteroventral extension of the metapleuron as variable within T. cosmopeplae and emphasized the shape of the gena in lateral view to separate these species. This modification to the key sought to reconcile variability in the shape of the gena with other, seemingly variable characters. The shape of the gena has proven to be one of the more difficult characters to interpret because there is not a discrete boundary between “narrow” and “bulging”. Because the variation in these characters does not correspond to clades in our phylogeny, we treat them as intraspecifically variable and the T. utahensis clade as a single species (Fig. 2 ). Based on the morphological analysis provided below we propose the following replacement for couplet 14 in Talamas et al. (2015):

14	Anteroventral extension of the metapleuron long, extending to base of mesocoxa (Fig. 6 ); mesoscutal humeral sulcus comprised of cells (Figs 6-7 )	T. cosmopeplae (Gahan)
-	Anteroventral extension of the metapleuron short, not approaching base of mesocoxa (Figs 12 - 19 ); mesoscutal humeral sulcus indicated by a smooth furrow (Figs 20-22 )	T. utahensis (Ashmead)

Sculpture of the dorsal frons.

Figs 8-11 illustrate variation in the size of the smooth area directly below the preocellar pit, and the striation that radiates from the antennal scrobe. Fig. 8 illustrates a specimen that emerged from a B. hilaris egg. As was found in T. basalis , specimens that developed in B. hilaris eggs have reduced sculpture relative to those that developed in other hosts ( Ganjisaffar et al. 2018). The specimens in Figs 9 , 11 were both reared from the eggs of P. maculiventris in British Columbia, and have identical COI barcode sequences, yet the size of smooth area on the dorsal frons differs between them. The specimen in Fig. 11 is the largest (1.35 mm) among these, and the specimen in Fig. 8 is the smallest (0.93 mm). The specimens in Figs 9 , 10 have the smooth area on the frons about equal in size and these specimens are also approximately equal in length (1.11 and 1.07 mm, respectively). These two specimens were retrieved in different haplogroups (clades 1 and 4), and we thus postulate that sculptural differences on the frons are size dependent.

Variation on the gena.

The shape of the gena varies between and within the four clades of T. utahensis . In clades 1 and 3, the specimens have a rather narrow gena, and in clades 2 and 4 the gena is moderately to distinctly bulging in lateral view. Figs 12-15 , 24 and 27 illustrate this variation. The degree to which the gena is bulging in lateral view does not appear to be host or size related. Specimens reared from B. hilaris eggs are the smallest and have the gena moderately (Fig. 12 ) to distinctly (Fig. 24 ) bulging. The specimens with the most distinctly bulging gena (clade 4, Figs 15 , 19 ) and the narrowest gena (clade 3, Figs 27 , 28 ) were both reared from eggs of P. maculiventris and the specimens are larger than those reared from B. hilaris eggs.

Specimens with a bulging gena tend not to have the genal carina indicated, whereas specimens with a narrow gena often have it clearly expressed, but this is not an exact correlation. The specimen in Figs 12 , 16 has a moderately bulging gena and the genal carina is distinctly present.

Microsculpture on the poster gena is less developed in specimens reared from B. hilaris eggs (Fig. 12 ), and this area is noticeably smoother than in specimens reared from P. maculiventris eggs (Figs 13-15 ). This phenomenon is consistent with a general pattern of reduced sculpture in smaller specimens.

Occipital carina.

Tortorici et al. (2019) presented a new character to distinguish T. semistriatus (Nees von Esenbeck) from closely related species: the form of the occipital carina in dorsal view. In most species of Trissolcus the occipital carina is evenly convex, but in a few species, including T. semistriatus and T. utahensis , the occipital carina forms a distinct angle and the vertex of this angle may have a short carina directed toward the median ocellus (Figs 5 , 22 ). In some specimens that emerged from B. hilaris eggs, the vertex of the angle formed by the occipital carina is less sharp, perhaps due to its diminutive size (Fig. 25 ). The occipital carina is not visible in the available images of T. cosmopeplae , and it is obscured by glue in the holotype specimen of T. utahensis . This character deserves further attention in Nearctic Trissolcus although we are not presently able to determine if it can separate T. cosmopeplae and T. utahensis .

Notaulus.

Specimens of T. utahensis reared from both B. hilaris and P. maculiventris have the notaulus indicated by short, shallow grooves present at the posterior margin of the mesoscutum (Figs 5 , 20-22 ). These are visible in the holotype of T. utahensis (see fig. 100 in Talamas et al. (2015)), and they have the same form in the holotype of T. cosmopeplae (Fig. 7 ). Based on re-examination of images of the types and the specimens at hand, we conclude that this character does not separate these species.

Mesoscutal humeral sulcus.

The form of the mesoscutal humeral sulcus was used by Tortorici et al. (2019) to separate very similar Palearctic Trissolcus species. This sulcus is clearly indicated by cells in the holotype of T. cosmopeplae (Figs 6 , 7 ) and it is present as a smooth furrow in all specimens of T. utahensis that we have examined (Figs 5 , 20-21 ), including the holotype.

Anteroventral extension of the metapleuron.

The length of this structure, reaching to the mesocoxa in T. cosmopeplae (Fig. 6 ) and very short in T. utahensis (Figs 12 - 19 ), was the first character listed in the couplet that separates these species in Johnson (1985). Our analysis of specimens in this study lends weight to the reliability of this character.

Color.

Most species in Trissolcus have a black metasoma. The most notable exception is a Palearctic species, T. rufiventris Mayr, in which T2-T7 vary from bright yellow to dark brown. The specimens reared from B. hilaris eggs have T2-T7 notably lighter in color than the head and mesosoma (Figs 20 , 25 ), and the body overall is lighter in color than in specimens reared from P. maculiventris eggs (compare Fig. 8 to Figs 9-11 , Fig. 12 to Figs 13-15 ).

The most obvious color variation in T. utahensis is in the legs. Specimens that parasitized B. hilaris eggs have legs that are pale brown to orange distal to the coxae (clades 1, 2; Figs 12 , 24 ). Brightly colored legs were found in T. utahensis that emerged from P. maculiventris eggs (clade 3, Fig. 29 ), although the clear majority of specimens reared from P. maculiventris eggs in British Columbia had dark brown legs. Interestingly, FSCA 00033239, with pale brown legs, in clade 1 is sister to FSCA 00000320, with dark brown legs. The antennae vary in color in accordance with the legs, although the variation is less pronounced and ranges from medium to dark brown. These data do not indicate that T. utahensis exhibits a direct correlation of appendage color with host, size, or lineage.

Material Examined.

11 females, FSCA 00091859, 00091872, 00094741-00094749, USA: CA: 33.99105N, 117.33360W, roadside mustard weeds, ex. Bagrada hilaris sentinel eggs deployed 6-9.IV.2018, parasitoids emerged 22-23.IV.2018, Coll. F. Ganjisaffar ; 1 female, FSCA 00033239, USA: CA: UC Riverside Agricultural Operations , 33.96611N, 117.34230W, squash field with mustard weeds, ex: Bagrada hilaris sentinel eggs deployed 12-16-X-2018; parasitoid emerged 27-28-X-2018, Coll. F. Ganjisaffar ; 9 females, 2 males, CANADA, BC, Penticton , reared from Podisus maculiventris , JUN-AUG-2017, Coll. W. Wong & P. Abram. Egg mass #181: FSCA 00094713-00094715, 00033042-00033043; Egg mass #144: FSCA 00000302; Egg mass #160: FSCA 00094712; Egg mass #92: 00033044-00033045; Egg mass #102; FSCA 00033040-00033041 . 1 female, FSCA 00094711, CANADA, BC, Kelowna , reared from Podisus maculiventris , 23.V.2017, Coll. W. Wong & P. Abram. Egg mass #171.

Figures

Figure 2. The Bayesian 50 % majority rule consensus tree inferred from the 56 CO 1 sequences of the six Trissolcus species including T. hullensis and T. utahensis. Only posterior probabilities> 90 % are indicated on the nodes. The tree is rooted with the outgroup Trissolcus thyantae (GenBank MN 615574). The scale bar corresponds to 0.1 estimated substitutions per site.

Figures 6 - 7. Trissolcus cosmopeplae, holotype female (USNMENT 00989096) 6 head and mesosoma, lateral view 7 head and mesosoma, dorsal view. Scale bars in millimeters.

Figures 12 - 15. Trissolcus utahensis, head and mesosoma, lateral view 12 DPI _ FSCA 00033239 (ex. B. hilaris) 13 FSCA 00033041 (ex. P. maculiventris) 14 FSCA 00000302 (ex. P. maculiventris) 15 FSCA 00033040 (ex. P. maculiventris). Scale bars in millimeters.

Figures 16 - 19. Trissolcus utahensis, head and mesosoma, ventrolateral view 16 DPI _ FSCA 00033239 (ex. B. hilaris) 17 FSCA 00033041 (ex. P. maculiventris) 18 FSCA 00000302 (ex. P. maculiventris) 19 FSCA 00033040 (e. P. maculiventris). Scale bars in millimeters.

Figures 20 - 22. Trissolcus utahensis 20 FSCA 00033239 (ex. B. hilaris), head, mesosoma, metasoma, dorsal view 21 FSCA 00033041 (ex. P. maculiventris), head, mesosoma, metasoma, dorsolateral view 22 FSCA 00033040 (ex. P. maculiventris), head, mesosoma, metasoma, dorsal view. Scale bars in millimeters.

Figures 8 - 11. Trissolcus utahensis, head, anterior view 8 DPI _ FSCA 00033239 (ex. B. hilaris) 9 FSCA 00033041 (ex. P. maculiventris) 10 FSCA 00000302 (ex. P. maculiventris) 11 FSCA 00033040 (Ex. P. maculiventris). Scale bars in millimeters.

Figures 23 - 25. Trissolcus utahensis (FSCA 00091872, ex. B. hilaris) 23 head, anterior view 24 lateral habitus 25 head, mesosoma, metasoma, dorsal view. Scale bars in millimeters.

Figures 26 - 29. Trissolcus utahensis (FSCA 00033042, ex. P. maculiventris) 26 head, anterior view 27 head and mesosoma, lateral view 28 head and mesosoma, ventrolateral view 29 lateral habitus. Scale bars in millimeters.

Figure 4 - 5. 4 Trissolcus hullensis (FSCA 00091886), head, mesosoma, metasoma, dorsolateral view 5 T. utahensis (FSCA 00000302), head, mesosoma, metasoma, dorsolateral view. Scale bars in millimeters.