Eventually, these tribesmen were brought to Margherita for using their labour in the construction of the historic Stilwell road from Ledo to Pangsau Pass (Indo-Mynanmar border). Some of these tribesmen died and the rest who survived never returned to their native land that is Nagaland and they settled down under Margherita sub-division. The word "Sema" originates from 'Sumi'. This martial race has a political system of an autocratic secular character, having a chieftain being characterized by benevolent disposition. Semas are generous, hospitable and frequently improvident. The main occupation of the Sema Naga tribe of Margherita sub division under Tinsukia District is cultivation and weaving. Presently, they are residing in nine beautiful villages of this district of Assam like Longton and Lalpahar villages.
. The Sema Naga Tribe celebrates many festivals, which have been carried down from generations. Most of these festivals usually mark the beginning of new seasons, harvesting of new crops or victory at war. The two major festivals that are currently popular among them are:
Ahuna is a traditional post-harvest festival of the Sumis or the Sema Naga tribs. Ahuna signifies the celebration of the season's harvest in Thanksgiving, while invoking the spirit of good fortune in the New Year. On this occasion, the entire community prepares and feast on the first meal of rice drawn from the season's harvest cooked in bamboo segments. Ahuna is celebrated on November 13 and 14 as one of the festivals of Sema Nagas. Although it now holds the status of the official festival of the Sumi Nagas because it falls in a dry season and accessibility for visitors in terms of road conditions are better.
Tuluni is a festival of great significance for the Sema Naga Tribe. This festival is marked with feasts as the occasion occurs in the bountiful season of the year. Drinking rice beer indispensably forms as part of the feasts. Rice beer is served in a goblet made of bamboo or made from the leaf of plantain. This drink is called Tuluni, which gives the festival its name. Tuluni is also called "Anni" the word of which denote the season of plentiful crops. Slaughtering of pigs and cows is an important feature of this festival. The practice of working in groups is common for the Sema Naga agriculture farmers, and Tuluni is a special time for them because they get to rest and celebrate the completion of a farming season of hard work in their paddy fields. The meat of the pigs and cows (Pork and beef) is equally divided among themselves and some portion is kept aside for the group feast. In the midst of the feast, group leaders get extra offer of meat by way of feeding them by others. Each working group consists of 20 to 30 in number, which includes several women too.