The biting midges are an extremely diverse group, with over 6200 species named worldwide. As for so many insect families, the number of described species is only a fraction of what is actually present in nature. Although it is a frequently asked question, it is difficult to know how many more species remain to be named. I would estimate that there are likely more than 12,000 species worldwide but this is only a “guesstimate”. There are several reasons for this uncertainty, as follows:
– There are many species already in collections which remain unnamed but there are just too few taxonomists working on this group to study all of these. Therefore we are even unsure how many unnamed species are in our collections. One thing that is certain is that many hundreds of unnamed species are present in established museums, waiting for a researcher to study them.
– Many areas, especially in the tropics, are poorly known (or haven’t been collected from at all!). Every major collecting expedition is virtually guaranteed to reveal new species. In many areas of the tropics and especially at mid or high elevations that have not been sampled before, often a majority of the species taken over an extended period of time are new (i.e. hundreds of new species). In fact, our understanding of biting midges is still so poor that even collecting in the high arctic, where diversity is much reduced, produces species which are unnamed.
– Some groups of biting midges, like the genera Dasyhelea, Forcipomyia and Atrichopogon have many named species. However, the descriptions by previous taxonomists (some of these in the 1800’s and early 1900’s) were so poor that we have little or no idea of which of these are actually valid species. This is why museums are so important as a repository for material of species after they are named; we often have to check later to see what a particular author was talking about, now that we have new material of perhaps the same or a new species.
– At the present time, taxonomists working on biting midges are mostly working at a morphological level (this means that we study the structures that we can see with regular microscopes). Consistent structural differences between groups of biting midges is taken as evidence of them belonging to different species (i.e. what looks consistently different is probably a different species). However, we know from detailed studies in non-biting midges, blackflies, mosquitoes and other better known groups of insects that often groups of individuals that look for all intents and purposes as identical are actually made up of 5, 10 or sometimes even more than 20 different species which can only be distinguished through the study of their genes (like barcoding). It is almost certain that many recognized species of biting midges that are identified on the basis of their larger structures are actually made up of a number of species (but how many no one knows!).
A few examples of diversity are informative. In Costa Rica, where I have studied over the space of numbers of years, at the present time our best estimates show that there are about 380 species which have already been named. Some of these are only known from Panama but are likely to be present in Costa Rica as well; others are known only from countries to the north and south (e.g. Honduras, Colombia) and are also therefore likely to be found in the intermediate area, including Costa Rica, as well. But what about unnamed species? In 2018, a major study of all the flies in 4 hectares of Costa Rican cloud forest was published, spearheaded by Brian Brown of the LA County Museum (USA) and myself. There were 4,332 species collected over the space of only one year and intensely studied by 59 specialists. The Ceratopogonidae were represented by exactly 200 species and together with Gustavo Spinelli and Florentina Díaz in Argentina, we are sorting out how many are undescribed. Initially it looks like more than 70% are new! Another small window into how diverse the group is was a sample of 69 species I collected in Carrasco National Park in Bolivia (on the eastern slope of the Andes) in 2016 over the space of 4 hours of sweeping an aerial net and virtually all were undescribed.