Mosha (Bengali: মশা) (transl. The Mosquito) is a work of science fiction written in Bengali by the novelist Premendra Mitra. The story was first published by Deb Sahitya Kutir, Kolkata, West Bengal, India, in the Puja Annual titled Alpana (Bengali: আলপনা) in 1945. Ghanashyam Das alias GhanaDa, the fictional character and the protagonist of the GhanaDa series of science-fiction stories appeared for the first time in this novel.

The character of Ghanashyam Das, also known as GhanaDa, is described as a bachelor with a dark complexion, tall and bony skeletal structure, and an age range of "anywhere between thirty-five to fifty-five." This description is provided by the author in Mosha, the first story of the GhanaDa series. He resided in the attic on the third floor of a shared apartment (Bengali: মেস বাড়ি) at No. 72, Banamali Naskar Lane, Calcutta, West Bengal, India. He lived alongside other boarders who affectionately called him GhanaDa, with "Da" being a Bengali suffix denoting respect and affection for an elder male. GhanaDa was rarely seen engaging in activities other than narrating fantastical tales to his fellow boarders. His stories encompassed most major world events of the past two hundred years, and he claimed to have visited nearly every place on earth.

গত দুশো বছর ধরে পৃথিবীর হেন জায়গা নেই যেখানে তিনি যাননি, হেন ঘটনা ঘটেনি যার সঙ্গে তাঁর কোনও যোগ নেই

Premendra Mitra, the creator of the character GhanaDa, described him in an interview with A. K. Ganguly published in SPAN in 1974, as follows:

Ghana~da is a teller of tall tales, but the tales always have a scientific basis. I try to keep them as factually correct and as authentic as possible.

One evening in Calcutta in 1945, the boarders of the shared apartment at No. 72, Banamali Naskar Lane gathered in the common room, engaging in casual conversation on various topics. Bipin, one of the boarders, mentioned the efforts to eradicate mosquitoes in his village. At that instance GhanaDa appeared upon the doorway. He was respectfully offered the lone armchair of the room, the best seat available, and a cigarette from Shishir as a loan. GhanaDa humbly stated that he had once killed one mosquito, the only one in his entire lifetime, on 5 August 1939, in the Sakhalin Island in Japan. All the listeners were overwhelmed and request him to narrate the story, and thus the story began.

In the story narrated by GhanaDa, he recounted being employed by a company in Sakhalin to collect amber in 1939. When a Chinese laborer named Tanlin went missing with a bag of amber, GhanaDa, along with Mr. Martin, the doctor, initiated a search. A Gilyak tribesman directed them to a scientific laboratory operated by Mr. Nishimara, an entomologist. It was revealed that Mr. Nishimara was genetically engineering mosquitoes to become agents of biological warfare, and Tanlin had fallen victim to one of his experiments. When a genetically modified mosquito landed on Mr. Nishimara's face and stung him, sealing his fate, GhanaDa killed the mosquito by slapping Mr. Nishimara. This act eliminated a significant threat to humanity. GhanaDa declared that he never intended to kill another mosquito for the rest of his life.

মশা মারবার পরিশ্রমেই যেন হাঁপিয়ে একটা দীর্ঘশ্বাস ছেড়ে ঘনাদা বললেন, "জীবনে তারপর মশা মারতে আর প্রবৃত্তি হয়নি"