Those who colonize mosquitoes are rightfully protective of them. Some species require a large amount of work to establish in the laboratory, and many of you have given your blood, sweat, holidays, and earnest attention to ensuring they exist. When you distribute it, you are giving a gift.
If vector biologists who had given time to colonizing and maintaining difficult stocks had just recompense for their donated effort to keep them, many would have retired already. These individuals have rescued stocks, controlled temperatures, carefully added diet and puzzled over low fecundity.
If you’re one of these people, you have added value to the wild mosquito counterpart by collecting it, selecting it and devising means to continue its culture for research purposes. The stock is yours. You own it. Why should you give it away?
Let’s consider that you might have received funding that requires you to distribute such material as part of the agreement. If so, you might have broken this agreement if you refused to do so. Don’t worry about it. Common.
Or you may be funded by a national government and could reasonably be expected to distribute your stock to others in your country or elsewhere because you are funded by the public for the public good. Well, we all have our programs to consider.
You might have been scooped by an unscrupulous colleague who used research material that you had provided to gain an advantage over you inappropriately, and you're not going to take that chance again. Understandable.
But consider these questions: Are others spending funds for research activities necessitated because you would not distribute your stock? How would those funds have been used otherwise? Are advances in the field not being made because you would not distribute your stock?
I personally know of examples of both of these and understand the personal and professional justifications given. However, if distributing your stock speeded the development of interventions against vector borne diseases, withholding them must be considered against the backdrop of the real death and suffering that is at stake. Are you certain that distributing your stock will contribute nothing toward reducing this burden? If so, why do you keep it? Don’t distribute your stocks for your colleagues. Do it for those at risk.
Your stock: your responsibility.