This is an updated overview of the New World (Western Hemisphere) members of Macrocentrinae. It is a revision of the keys by Wharton (1997) and Sharkey et al. (2021a) and contains a synopsis of each genus. The synopses include the following sections: diagnosis, biology, diversity, distribution, publications, and notes. There are four genera reported from the New World.

Wharton, R.A. 1997. Subfamily Macrocentrinae, pp.310-313. In: Wharton, R.A., Marsh, P.M., and Sharkey, M.J. (eds). Manual of the New World Genera of the Family Braconidae (Hymenoptera). Special Publication of the International Society of Hymenopterists, 439 pp.

Sharkey, M.J., Janzen, D.H., Hallwachs, W., Chapman, E.G., Smith, M.A., Dapkey, T., Brown, A., Ratnasingham, S., Naik, S., Manjunath, R., Perez, K., Milton, M., Hebert, P., Shaw, S.R., Kittel, R.N., Solis, M.A., Metz, M.A., Goldstein, P.Z., Brown, J.W., Quicke, D.L.J., van Achterberg, C., Brown, B.V., and Burns, J.M. 2021a. Minimalist revision and description of 403 new species in 11 subfamilies of Costa Rican braconid parasitoid wasps, including host records for 219 species. ZooKeys, 1013: 1-665. https://doi.org/10.3897/zookeys.1013.55600

Macrocentrinae is a moderately diverse subfamily containing four genera in the New World. Most of the described species belong to the genus Macrocentrus Curtis. Ahlstrom (2005) revised the species of North America north of Mexico, updating Muesebeck (1932). The latest generic synopsis is by van Achterberg (1993). Shaw and Huddleston (1991) provide a useful summary of the literature, with special reference to biology. New World specimens of Braconidae can be identified to subfamily using the key by Sharkey et al. (2023). Readers using that key will be automatically directed here if they obtain an identification of Macrocentrinae. The present work includes a key to the four New World genera, and a synopsis of each genus. The synopses include the following sections: diagnosis, biology, diversity, distribution, publications, and notes. Images are by Sharkey. General morphological terminology can be found in Sharkey et al. (2023) and in the Hymenoptera Anatomy Ontology Portal (http://portal.hymao.org/projects/32/public/ontology/).

Phylogeny

No phylogenetic analyses at the genus level have been conducted. In a molecular phylogenetic study, Sharanowski et al. (2011) recovered Macrocentrinae as sister to Xiphozelinae and these were found to be sister to the clade Amicrocentrinae + Charmontinae.

Biology

The Macrocentrinae include both solitary and gregarious koinobiont endoparasitoids of lepidopterous larvae (Clausen, 1940; Shaw and Huddleston, 1991). Where known, the gregarious species are polyembryonic. Detailed biological information is available for two species, M. ancylivorus Rohwer (Daniel, 1932; Finney et al., 1947) and M. cingulum Brischke (as referred to in recent literature van Achterberg, 1993; Farahani et al., 2012) or with authorship incorrectly attributed to Reinhard or as M. grandii Goidanich (Parker, 1931; Ding et al., 1989) or as M. gifuensis Ashmead (a misidentification) in some of the more important earlier publications. Although only a single individual of M. ancylivorus emerges from its host, initial development is polyembryonic (Daniel, 1932). Details of the development of other macrocentrines are largely unknown. It is possible, however, that those species that emerge as solitary parasitoids (at least in Macrocentrus and Hymenochaonia Dalla Torre) are initially polyembryonic in their development. New World macrocentrines have been reared from 10 families of Lepidoptera (Yu et al, 2016; Sharkey et al. 2021a).

Many of the macrocentrines are pale colored and crepuscular to nocturnal. The species of Macrocentrus and Hymenochaonia have long ovipositors, often laying their eggs in early instars of hosts concealed in leaf whorls, stems, tubers, or rolled leaves. Austrozele Roman and Dolichozele Viereck, on the other hand, have short ovipositors, and the available records indicate that they attack exposed caterpillars, e.g., Arctiidae and Noctuidae.

Common genera

Macrocentrus and Hymenochaonia are the major New World genera. There are about 190 described species of Macrocentrus worldwide, and about one-fourth of these occur in the New World. The remaining 46 species of described macrocentrines are divided amongst seven other genera worldwide. We estimate that there are several hundred or more undescribed New World species.

Distribution

Cosmopolitan.

Distinguishing features

Macrocentrines can be recognized by the absence of an occipital carina and the presence of small teeth on the hind trochantellus (Fig. 1). With the exception of one known species, M. incompletus Muesebeck, all described species have three submarginal cells.

Note: In the generic treatments we give rough estimates of the number of undescribed species that may occur in the New World, e.g., “There are 26 BINs (proxies for species) from Costa Rica on the Barcode of Life Data System (BOLD, Nov. 25, 2024), and we estimate that there may be a hundred or more undescribed species in the New World.” To arrive at these very conservative numbers we used estimates of the number of trees in Costa Rica compared to the remainder of the New World. Cazzolla Gatti et al. (2022) estimated there to be 40,123 species of trees in the New World. Nelson Zamora (personal communication), the leading Costa Rican botanist, estimates there to be 2,500 species of trees in Costa Rica, or ~6.2% New World fauna. Over the last ten years Dan Janzen, Winnie Hallwachs and their team have barcoded Malaise trap samples from all over Costa Rica, making it the best sampled country on the Barcode of Live Data System database, though it is far from complete. In the example above, if we were to assume that the 26 BINs represented 6.2% of the New World fauna we would arrive at an estimate of 419 species for the New World. However, we refrain from this detailed estimate and instead make the generalized and conservative estimate of “a hundred or more.”

Table 1. List of New World genera of Macrocentrinae

 Austrozele Roman, 1910

 Dolichozele Viereck, 1911

 Hymenochaonia Dalla Torre, 1898

 Macrocentrus Curtis, 1833