|photo from https://upload.wikimedia.org/wikipedia/commons/1/17/Breads_(1).jpg|
Hashem then sends venomous snakes who bit them. The people confessed there sin and appealed to Moshe who appealed to Hashem who told him to fashion a snake and put it up on a pole.
What is the connection between complaining about mann and being subjected to snake bites? In what way did the punishment fit the crime?
A number of different answers can be found among the commentators, including references to the orginal nachash who is condemned to eat dust of the earth, but this is the one that occurred to me:
The nachash was also told וְאֵיבָה | אָשִׁית בֵּינְךָ וּבֵין הָאִשָּׁה וּבֵין זַרְעֲךָ וּבֵין זַרְעָהּ
Bnei Yisrael complained about the mann, the Heavenly bread that could be eaten without the labor of planting, cutting, winnowing, grinding, kneading, and baking entailed in the bread we normally eat. They wanted a more standard diet with earthly bread. Consequently, Hashem told them that they would also get the rest of that package deal. They would no longer get divine protection from the very natural danger of snakes bite.
For a take on bread as the symbol of human work, see http://kallahmagazine.blogspot.com/2012/01/natural-vs-man-made.html