It is broadly accepted that new species description of e.g. Chironomidae, are based at least on adult males, but many researchers work mostly with larvae. When large number of larvae are analysed in ecological investigation, often strange unknown specimens are found. They are potentially new species, sometimes they are so strange that we suppose that they might be new genera. But we never know if they aren't just larvae of species described on adult male. Should we just omit this specimens in datasets, or throw them out as unnecessary trouble? What we can do? Does describing "new larvae form" as for e.g. "Orthocladiinae larval form 1" make sense?
If they aren't preserved, you could try rearing them. That way, you might acquire males, females, pupae and larvae for a full description of all stages, closing the net on that particular species. If this is not practical (for reasons of time, facilities etc) then you could label them as morpho-species (something like sp1, sp2, sp3 etc), but I would caution against throwing them away. If you do throw them away, then there is no permanent record and nobody will ever be able to compare their data with yours at a later date when the species are described and more is known about them. They might also be very rare, many species are known only from the holotype - once thrown away, they are lost forever. At least if they are lodged in a museum, they are there for perpetuity and could, in years ahead, form the foundation of a whole new research project.
I don't know that there is anything particularly wrong with describing the new larvae out of context of the adults - at some future stage these could be married up with adults and, if necessary, the more recent name sunk into synonymy with the earlier precedent. On the other hand this could also lead to some confusion until such resolution is found, because it might be difficult to link larval descriptions with already described or otherwise undescribed adults (as is the case in sexually dimorphic species where males and female descriptions exist and require considerable taxonomic sleuthing to combine) and there might be some resistance from Chironomid researchers to such descriptions because of this. If you scan the taxonomic literature for Chironomidae, you'll get an idea of how often descriptions based purely on larvae occur and this might give you some guidelines.
On a pragmatic stance, my inclination as a taxonomist, is to say go ahead, get a name on it - it gives everyone a handle with which to manage the larva of the species, even if this later has to be sunk into synonymy with an existing description based on an adult, or the other way around, at a later point a description based on a male has to be sunk with the name given to the larval stage you describe now. It happens all the time, and yes, it causes temporary taxonomic confusion and artificially swells the numbers of species in a genus, but at least you have a reference point (i.e. a name, rather than a nebulous sp1). The difficulty with morpho-species designations is that everybody starts with sp1 and it takes much more effort to check all the sp1s (if you can even find them all) than to read a diagnosis of a species. In balance then, describing the species on the larval stage has more weight than using a temporary morpho-species designations and very much more than ignoring the specimens and throwing them out, especially if, as you say, they are highly distinctive and unusual.
Thank you! that is what I really think. But I often hear that even faunistic data base on larvae are not good enough and when I don't have the adults I can't say much. I think many chironomid taxonomists don't accept describing new species on larvae. It is the best to rear imagines when you have living larvae determined, but often I get larvae conserved in alcohol, from somewhere far away I can't get easily. Then I think the best is to make drawings, description and to publish it with rest of a data, and put specimen to the collection.
Mateusz, that is exactly what we used to do. But then one could have to wait for a very long time before someone matches the adults and the larvae.
Rearing is not very hard, but rearing individual specimens so that the adult can be matched with the pupal exuviae and with the larva is much more cumbersome.
That is what I plan start to do. Some times I receive collections of larvae from Montenegro. I hope some day I will go there for longer to collect living material from this sites and breed them. This could give much more faunistic information than determining only larvae. But even when only larvae are available it is very interesting.
Rearing is one -and a great- option, but alternatively one can also use DNA barcoding of the midge larvae. This way, depending on the availability of the midge barcode database, it is possible to obtain adult-larva matches. New sequencing platforms, and experimental techniques kind of democratize the sequencing world with getting more and more cheaper. Here is a very useful paper, describing the experimental procedure, applied on chironomid midges, and its potential identifying the specimens while retaining their morphology.
http://onlinelibrary.wiley.com/doi/10.1111/1755-0998.12275/abstract;jsessionid=FA72AB69650EE79F3607A187A5DAFE65.f02t03
Technically larva can be designated as Holotype. Now key are available for all the stages and one can identify larval forms easily.
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