Megaphragma wolfi Lahey & Polaszek, 2025

Lahey, Zachary, Polaszek, Andrew, Fusu, Lucian, Simmons, Alvin M. & Andreason, Sharon A., 2025, A new, apterous species of Megaphragma Timberlake (Hymenoptera: Chalcidoidea: Trichogrammatidae), Journal of Natural History 59 (1 - 4), pp. 99-111 : 102-106

Megaphragma wolfi Lahey & Polaszek , sp. nov.

https://zoobank.org/ 41966092-7058-44DF-8B21-6E6A4DD18E85

( Figures 2–8 )

Diagnosis

Both sexes wingless; tegulae absent. Male antenna with 6 antennomeres, three-segmented clava, and C1 approximately 3× length of C2 (male of M. giraulti with 5 antennomeres, two-segmented clava, and C1 approximately 2× length of C2; males unknown in other polychaetum -group species). Female antenna with 5 antennomeres and clava two-segmented. C1 with one UST (females of M. giraulti , M. kinuthiae and M. polychaetum with two UST on C1) and no apparent MT (female of M. giraulti with ≥10 MT on C1).

Description

Male. 200–250 µm long. Body largely pale brown, metasoma darker, especially metasomal calluses.

Antenna ( Figure 3 ) with six antennomeres, excluding the conical anellus; elongate funicle present; clava three-segmented. Funicle with one MT; C1 and C2 each with one minute MT; C3 with two very long MPS and two SB.

Head with prominent ocular seta (os: Figure 4 ); genal seta present (gs: Figure 4 ). Midlobe of mesoscutum entirely smooth, laterally with two pairs of long setae ( Figure 8 ). Propodeum without crenulae and with long seta adjacent to spiracle ( Figure 8 ). Metasoma with a pair of reticulate calluses on each tergite ( Figure 2 ). All tarsi longer than corresponding tibiae; apical tarsal segment the longest, fore leg with basitarsus much shorter than basitarsus of mid and hind legs. Wings absent, with no apparent trace of vestiges or tegulae.

Female. 230 µm long. Metasoma paler than in male. Antenna ( Figure 6 ) with five antennomeres, excluding the conical anellus; conical funicle present, slightly longer than greatest (apical) width, with one MT; clava with two antennomeres; C1 with one UST and one ASC; C2 with two MPS and two SB. Metasoma without calluses; fore basitarsus shorter than corresponding segment in the male. Ovipositor length equal to mid tibia length.

Material Examined

Holotype ♂ (deposited in NHMUK). USA: South Carolina, Charleston, U.S. Vegetable Laboratory , 32°46′36′′N, 80°3′39′′W 26.iv.2023 Z. Lahey Z378 OSUC 863878 ( NHMUK) . Paratypes 1 ♀ ( OSUC 864114 ), 1♂ ( OSUC 864115 ), same data as holotype ( NHMUK); 3♂♂ same data as holotype except 1♂ ( OSUC 863877 ) 28.iv.2023 ( UCRC) 2♂♂ ( OSUC 864116 , 864,117 ) 1.v.2023 ( USNM; NHMUK). 1♂ COSTA RICA: Puntarenas, Las Cruces, Wilson Botanical Garden , 8°46′N 82°57′W 1300 m JS Noyes ii.2015 BMNH (E) 2015–57 ( NHMUK).

Species-group placement. Megaphragma polychaetum -group ( Polaszek et al. 2022).

Distribution

Costa Rica; South Carolina ( USA).

Host. Unknown.

DNA data. COI: six sequences; 28S: six sequences (all from South Carolina, USA).

Etymology

Named for Wolf Xavier Polaszek Nieuwenhuijse, grandson of the second author (AP). The epithet is treated as a noun in the genitive case.

Comments. The only wingless trichogrammatid female known to us is that of M. wolfi . In addition to Megaphragma , aptery has been recorded in males of three other genera: Prestwichia Lubbock , Trichogramma Westwood and Monorthochaeta Blood ( Doutt and Viggiani 1968; Pinto 2006). Morphologically, the males of M. wolfi are most likely to be confused with those of Prestwichia due to overall size, similarity in habitus and structure of the antenna, but only the last character can be used to differentiate wingless species of the two genera. The antenna of Megaphragma has a maximum of three postannelar segments (some species with two), whereas Prestwichia always has four postannelar segments ( Pinto 2006; Polaszek et al. 2022).

Phylogenetic Analyses. Single (COI, 28S) and combined (COI+28S) phylogenetic analyses were conducted on 180 Megaphragma specimens and nine outgroups. Seven specimens, six of which belong to M. wolfi and one belonging to a member of the M. ghesquierei -group, were newly sequenced for this study and were incorporated into the molecular dataset analysed by Polaszek et al. (2022). The 28S alignment contained 164 Megaphragma sequences and was 955 characters (bp + gaps) in length. The best-fit nucleotide substitution model for this analysis was TIM3e+R4. The COI alignment contained 120 Megaphragma sequences and was 651 characters (bp + gaps) in length. The 1st and 2nd codon positions of COI were merged into a single partition under the TVM +F + I+ G4 substitution model, and the best-fit substitution model of the 3rd codon position was K3Pu+F+ R2. The combined analysis contained terminals for 189 specimens (180 Megaphragma and nine outgroups) and was 1,606 characters (bp + gaps) in length. Three partitions were specified in this analysis: (1) 28S (GTR+F+ R4); (2) the 1st and 2nd codon position of COI (TVM+F + I+ G4); and (3) the 3rd codon position of COI (TIM+F+ R4).

Relationships between Megaphragma species and species groups in our analyses largely mirror those of Polaszek et al. (2022). We limit our discussion of these relationships to the results obtained by us in the combined molecular analysis since this dataset is the most comprehensive in the number of characters and taxa evaluated (see Supplementary Material for single gene phylogenies). Two major clades were recovered in our analysis ( Figure 9 ). The first major clade was composed of M. liui Polaszek & Fusu ( ghesquierei -group), members of the polychaetum -group, two undescribed species that Polaszek et al. (2022) posited belong to the polychaetum -group and the monophyletic mymaripenne -group. The second major clade recovered was composed of the monophyletic antecessor -group and the ghesquierei -group, which was rendered paraphyletic by the antecessor -group and the placement of Me. liui as the sister to all other Megaphragma . Megaphragma wolfi was recovered within the polychaetum -group as the sister taxon to M. cockerilli Polaszek & Fusu , a result highly consistent with its antennal morphology.

Our results deviate from Polaszek et al. (2022) in the placement of the antecessor -group as the sister taxon to the ghesquierei -group, whereas Polaszek et al. (2022) recovered the antecessor -group as the sister taxon to the polychaetum + mymaripenne -groups. This result may be due to the inclusion of a ghesquierei - group species from Congo for which only 28S is available. The position of M. liui as the sister to the remaining Megaphragma is also quite different than its placement as the sister taxon to the antecessor -group in Polaszek et al. (2022), potentially because M. liui is represented by a single, short COI sequence in our analyses compared with their study that also included a short 28S sequence. The M. liui 28S sequence was removed from our dataset prior to alignment because it behaved inconsistently in pilot analyses, frequently rendering the genus paraphyletic by grouping with Prestwichia in both single gene (28S only) and combined phylogenies.

Figures

Figure 9. Maximum likelihood phylogeny of combined 28S and COI sequences in 180 Megaphragma specimens and nine outgroup taxa. Species group placement of Megaphragma specimens is indicated at terminals. The number under the scale bar indicates the number of expected nucleotide substitutions per site. Ultrafast bootstrap support values are indicated by coloured circles at nodes.

Figure 2–5. Megaphragma wolfi Lahey & Polaszek, sp. nov. 2. Holotype male, lateral habitus (arrow indicating metasomal callus). 3. Holotype male, antenna, lateral view. 4. Paratype male, head, anterior view. 5. Paratype female, lateral habitus.

Figure 6–8. Megaphragma wolfi Lahey & Polaszek, sp. nov. 6. Paratype female, antenna, lateral view. 7. Paratype male, hind leg, lateral view. 8. Paratype male, mesoscutum, lateral view.