This is an updated key to the 36 subfamilies of Braconidae found in the New World (Western Hemisphere). This includes Greenland and the Caribbean Islands. It is a revision of the key by Sharkey, (1997) found in the manual of the New World genera of the family Braconidae (Wharton et al., 1997). The key is fully illustrated and is meant to facilitate use by non-specialists; the online version additionally follows web accessibility standards and is usable on desktop and mobile devices. This represents the first of a series of publications, the rest of which will focus on each braconid subfamily. Each of these publications will include an overview of a subfamily, an illustrated key to its genera, and one or several pages dedicated to each genus with extensive illustrations. As each of these 36 keys is published, the online version of this publication will be updated with links to lead readers to the appropriate subfamily publication.

Sharkey, M.J. 1997. Key to the New World subfamilies of the family Braconidae, pp. 39-63, In: Wharton, R.A., Marsh, P.M., & Sharkey, M.J. (eds). Manual of the New World genera of Braconidae (Hymenoptera). Special Publication of the International Society of Hymenopterists, 439 pp.

Wharton, R.A., Marsh, P.M., & Sharkey, M.J. (eds). 1997. Manual of the New World genera of Braconidae (Hymenoptera). Special Publication of the International Society of Hymenopterists, 439 pp.

Histeromerus sp. (Rhyssalinae), Fergus, Ontario by S.A. Marshall

Literature Background

Wharton et al. (1997) published the “Manual of the New World Genera of the Family Braconidae”. This was updated in 2017 and published with Amazon (Wharton et al. 2017; link in References). This latter version includes an addendum at the end of each subfamily chapter that updates the subfamily treatment with new literature citations and changes in taxonomic nomenclature, e.g., new genera, changes in subfamily composition. The present publication, treating the Braconidae as a whole, is the first of a series of publications that will completely revise the Manual.

Diversity

The Hymenoptera are a diverse order of insects, and probably the most diverse order after Diptera (Hebert et al. 2016), despite arguments suggesting that Hymenoptera is the most diverse (Forbes et al., 2018). For example, Figure 1 shows the relative number of species of insects (estimated by COI barcodes) by order captured by Malaise traps in the Área de Conservación de Guanacaste (ACG), in northwestern Costa Rica (Janzen & Hallwachs, 2011, 2019). Although beetles may be underrepresented in Malaise traps it seems clear that Diptera are the most diverse order followed by Hymenoptera, Coleoptera, and Lepidoptera.

Within the Hymenoptera there are four higher taxa with similar species diversity in the same area, Chalcidoidea, Ichneumonoidea, Platygastroidea, and Aculeata (Fig. 2). Together these constitute more than 70 percent of all Hymenoptera surveyed in the ACG. Amongst the families of Hymenoptera, the Braconidae are the most diverse in ACG with 1,742 species, followed by the Ichneumonidae with 1,113 species. Data from other areas may differ from ACG but, based on worldwide data on BOLD, there is little question that braconid parasitoid wasps are among the most species-rich groups of Hymenoptera.

Here we treat the braconid subfamilies that occur in the New World (North, Central and South America). These vary greatly in their species richness. Figure 3 is a bar graph of the number of species of the subfamilies in ACG, and Figure 4 presents a bar graph of the number of species of the subfamilies captured in Malaise traps in Canada (Hebert et al. 2016). In Costa Rica the Doryctinae are the most species-rich, whereas in Canada they are in a distant ninth place. Conversely in Canada (Fig. 4) the most species-rich subfamily by far is the Alysiinae. In both areas the Microgastrinae are in second place, and it may be the most species-rich subfamily overall. These diversity statistics are probably similar across northern temperate and tropical areas in the Americas and are worth noting when attempting an identification.

Biology

The message of the numbers detailed above is that Braconidae is an extremely diverse family in terms of species richness (Jones et al., 2009). They are also diverse in their biologies. Most are parasitoids of other holometabolous insects and of these most are attacked in the larval stage. However, there are numerous exceptions to these generalizations. Paurometabolous insects in adult or nymphal stages may act as hosts (e.g., for Aphidiinae and some Euphorinae), and egg (e.g., for Cheloninae, some Brachistinae, and a few Microgastrinae) or adult (e.g., most Euphorinae) stages may be attacked. Those that attack the egg stage delay their own development until the host larva is well developed; there are no true egg parasitoids. Even stranger, there are several independent developments of phytophagy within Braconidae (Samacá-Sáenz et al., 2022). There are also rare examples of hyperparasitoids, i.e., parasitoids of parasitoids, e.g., some Alysiinae that attack Tachinidae. Parasitoid braconids, the vast majority of braconids, are classified as either idiobionts or koinobionts. Idiobionts begin their development immediately after the egg is laid whereas koinobionts delay their feeding and development allowing the host to grow to an appropriate size or stage. Parasitoids are also classified as endo- or ectoparasitoids. Those that feed on the host internally are endoparasitoids and those that feed externally are ectoparasitoids. All of these biological traits and more will be discussed in detail in the subfamily and generic treatments in future publications. Details of braconid biology can be found in publications by Mark Shaw and Tom Huddleston (Shaw and Huddleston 1991), Bob Wharton (Wharton 1993) and Donald Quicke (Quicke 2015).

Classification

There have been a number of recent works on the phylogeny of the Braconidae (Jasso-Martínez et al. 2022, and references therein) and these have resulted in changes in classification at the subfamily level. Here we recognize 36 subfamilies as occurring in the New World, which are listed in Table 1. In the manual of New World Braconidae (Wharton et al., 1997) 34 subfamilies were recognized. The differences are the result of the following changes. The subfamilies Adeliinae, Betylobraconinae, Blacinae, Histeromerinae, Meteorinae, Neoneurinae and Ypsistocerinae have lost their subfamily status and have been placed in other subfamilies from which they are derived. The following list includes the parent subfamily in parenthesis: Adeliinae (Cheloninae), Betylobraconinae (Rogadinae), Blacinae (Brachistinae), Histeromerinae (Rhyssalinae), Meteorinae (Euphorinae), Neoneurinae (Euphorinae) and Ypsistocerinae (Doryctinae). There are also new subfamilies introduced or more generally accepted since 1997, i.e., Brachistinae, Charmontinae, Exothecinae, Lysiterminae, Mesostoinae, Pambolinae, Rhysipolinae, Rhyssalinae. Most of these come from the breakup of the formerly polyphyletic Hormiinae. Finally, the subfamily name Gnamptodontinae has been changed to Telengaiinae.

There are several informal groups in the Braconidae. Amongst these are the cyclostoma (or cyclostomes), orthostoma (or orthostomes), endodont braconids, and exodont braconids. Images of these are in Figure 6.

Catalogues and Other Resources

There are numerous catalogues dealing with the Braconidae, all of which are outdated. Yu et al. (2016) created an electronic database that incorporated data on the Ichneumonidae and Braconidae. Unfortunately, there have been no updates since 2016. The Yu et al. (2016) database can be obtained from most of the authors of this publication and certainly by senior author Sharkey (msharkey@uky.edu). On the bright side, the internet has become increasingly effective as a taxonomic resource. Google Scholar and the Biodiversity Heritage Library (https://www.biodiversitylibrary.org) are invaluable. Ghahari et al. (2006) published a bibliography of the Braconidae that deals with literature from 1964 through 2003. A link to this is given in the references.

Identifying New World Braconidae

Only the largest specimens of Braconidae can be pinned in the conventional manner, i.e., with the pin pierced through the thorax. All other specimens should be point-mounted to permit identification. For larger specimens, the tip of the paper point may be angled downward to provide more surface area.

The keys in this publication and the subfamily treatments that will follow in the near future will allow for the identification of braconids to the levels of subfamily and genus. Beyond that we will be presenting a list of published keys for each genus. Unfortunately, we estimate that fewer than a quarter of the northern temperate New World species and less than 3% of the tropical and southern temperate species are described. Moreover, the literature containing descriptions and keys is often oversimplified. In short, the task of identifying a braconid to species is usually an impossible one. Despite this state of affairs, one tool has revolutionized identifications: Barcode Of Life Data Systems (BOLD) (Ratnasingham and Hebert 2007). To obtain an identification using BOLD, one simply obtains a COI sequence for the specimen and submits the sequence as a query at the following URL: http://www.boldsystems.org/index.php/IDS_OpenIdEngine. Presently, this will give the user the generic name of about 80% of New World braconids, and almost all of the common genera, but few species names. There is a serious initiative to barcode the type specimens in many major museums and we suspect that in less than a decade BOLD will be dense with barcodes associated with species names. This will almost certainly be the method of choice for braconid identification in the future. It will be interesting to see if there will be any value in the future for the key presented here and those at the generic level that will follow over the next months. In any case, they have been a joy and an intellectual challenge to create and the database at BOLD would not have been created without keys such as these. In cooperating with BOLD, we as taxonomists do not mind committing partial intellectual suicide. With the advent of artificial intelligence, many enterprises such as the work associated with this publication will, no doubt, become archaic. Readers may consider this a depressing thought, but it need not be. In an ideal future, naturalists will be able to collect braconid specimens in their back yards and create inventories in days. Laypersons will be able to identify braconids and other insects to the species level and appreciate, to a much greater degree, the treasures under their protection

Table 1. List of subfamilies of Braconidae recognized as occurring in the New World.

Every attempt has been made to illustrate each character in the key such that laypersons can use the key without a knowledge of specialized jargon such as vein RS, pronotum, first tergum, etc. Nonetheless, we include a few images from the morphology chapter in the 1997 manual (Sharkey and Wharton, 1997) for those readers interested in having a more comprehensive understanding of braconid morphological terminology (Figs 5-9). There is also an online resource, the Hymenoptera Anatomy Ontology Portal (Seltmann et al. 2012), available at: http://portal.hymao.org/projects/32/public/ontology/. Here you can enter a morphological term and select it from a picklist. This will direct you to the definition and an illustration of an example of the character.