November 12, 2012

An overview of braconid wasps in Canada

Braconid wasps are the second largest group within Hymenoptera (the insect order that comprises bees, stinging wasps, ants, sawflies and parasitoid wasps). The last version of Taxapad records 956 described species of Braconidae for Canada. Of course, that is just the total of species that have been given scientific names by taxonomists. But it does not account for the many undescribed and/or unrecorded species that remain to be discovered. How many species are actually out there in the Great White North?  

Main subfamilies of Braconidae (Hymenoptera) in Canada. Total number of species: 956 [based on Taxapad (2012)].
While it is impossible to be certain, it is likely that at least twice the current figure, or about 2,000 species of braconid wasps will be found in Canada when all is said and done. 

Think about that for a second. The only group of living things (excluding perhaps microorganisms) that is more diverse than braconids wasps is yet another group of parasitoid wasps: Ichneumonidae, which happens to be the sister group to braconids. Ichneumonid wasps currently comprise almost 3,000 species in Canada (2,834, according to Taxapad). Nothing else comes even close to those figures -and the same situation is probably found in most other areas of the planet. We are talking here about the biodiversity heavy-weights.

Two thousand species of braconid wasps in Canada is a great number, and it amazes to think that we are still missing ONE THOUSAND species to be recorded -let alone studied in detail! The vast majority of those tiny wasps play a capital role in the natural regulation of herbivores -which might otherwise become pests of our crops and forests. Thus, this is not only a matter of scientific inquiry, but also a practical issue with economical implications. 

The sad thing is that there is not much support for taxonomic studies these days. Even groups that are economically important have been neglected for years -sometimes decades. As a result, our capacity to deal with pest outbreaks, new invasive species and the ultimate sustainability of our ecosystems is compromised. 

This blog is a humble effort to try to fill (even if partially) one of those gaps, namely the study of braconid wasps. The initial emphasis will be on species parasitizing Lepidoptera (the insect order that groups moths and butterflies) because of the impact that caterpillar pests have in Agriculture and Forestry. Roughly half of the braconids in Canada (or 500 species) are parasitoids of lepidopterans, making them one of the most important groups in biocontrol. 

[The other half of the braconid species in Canada parasitizes different groups of insects (e.g. aphids, beetles, bugs, sawflies, etc). But they will not be dealt with here for the time being -unless there is great demand or need to cover those groups in the future].

The geographical focus will be mainly Canada, but it will also be expanded to the whole Nearctic (North America) and eventually the Palearctic (Europe and northern Asia) because of the close relations between species living in those areas.

Let me briefly mention the most common subfamiles of Braconidae parasitizing caterpillars in Canada, and its use (or potential use) in biological control programs. 

Main subfamilies of Braconidae (Hymenoptera) in Canada parasitizing caterpillars (Lepidoptera). Total number of braconid species: approximately 500 [based on Taxapad (2012), and unpublished data from this blog]. The subfamily Braconinae contains a significant number of species (probably half of its species) which do not attack Lepidoptera but other insect orders, especially Coleoptera (beetles).
1- Microgastrinae. One out of four species of Canadian braconids are microgastrines; and if you only consider those species parasitizing Lepidoptera, then  half of the braconid are microgastrines. The latest compilation of species for Canada estimates the total number at around 500. Because of its diversity and significance in biocontrol (they are the single most important group of parasitoid wasps attacking Lepidoptera) most of this blog will deal with microgastrines. 

2- Cheloninae. A group easily recognized by its carapace-like metasoma (although not all braconids with such a feature belong to this subfamily). As with microgastrines, chelonines only parasitize Lepidoptera, and some species (mainly from the genus Chelonus) are frequently and commonly used in biocontrol, mainly against agriculture pests. In Canada, roughly one out of eight braconid species parasitizing caterpillars is a chelonine wasp.

3- Rogadinae. This group of wasps is unique because they mummify the remains of the host caterpillar. Included here is the diverse genus Aleiodes, with some species of importance in the natural control of forestry pests, but very few studies done on the topic so far. Currently rogadines comprise one tenth of the caterpillar parasitoids in Canada, but that number is likely to increase when more studies are done.

4- Agathidinae. Included here are some of the largest specimens of braconid reared from caterpillars, and the group is very distinctive based on the venation of the fore wing -among other features. Many members have been used in the classical biological control of pests in both agriculture and forestry.

5- Macrocentrinae. A group extensively used in the biocontrol of gelechiids, pyralids and tortricids caterpillars. The large genus Macrocentrus was recently (in 2005) revised for North America (46 species, including 27 recorded for Canada), but it is quite likely that many more species await for description.

6- Genus Meteorus. The placement of this genus within a subfamily has varied through the years, but regardless of the discrepancies between taxonomists, Meteorus comprises species of importance in the natural control of forestry caterpillars -although less so in agricultural areass.

In following posts, more information about the above-mentioned groups will be shared.  

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