Well, there only one concerned authority. You can communicate is ZSI, Dr. Shila Scientist-C in Kolkata. I suggest to do some immature character observation, by which you can isolate before adult form. I did not understood intermediate form, is it pupa or imago form?
It seems you are new to mosquito research. Anopheles stephensi is the urban malaria vector in India. It exists in 3 morphologically identical (sibling species) forms in India. I know Dr. Sheela. She has nothing to do with mosquitoes. She was my junior at university of Calicut. Anyway, thank you for your willingness to help.
Taxonomic debate on the species status of Anopheles stephensi is over. i laboratory rear mosqitoes one can find all the genetic variants of An. stephensi. was able to document 59 morphological and genetical variants in this species reference is as follows