Reverse Google Image Search immediately brings up:
The Chitauri are a cybernetic alien race governed by a hive mind and
subservient to the overlord Thanos. They were led by the Asgardian
Loki during the War for Earth but were defeated by the Avengers.
The Chitauri are a powerful, reptilian warrior race, a hybrid between organic beings and machines
Furth research in that vein reveals the giant worms are Leviathans:
Leviathans are extraterrestrial animal-slaves and warships for the
Chitauri. Not much about them is known, only that they are
cybernetically-enhanced beasts which aid the Chitauri during their
attempted invasion of Earth.
From the another Chitauri wikia page:
Their troop transports take the form of the Leviathans, very large
serpent-like creatures. These Leviathans can carry hundreds of
Chitauri infantry, and are quite durable. However, they do not have
any weaponry aside from simply ramming their target, and are shown to
be vulnerable to large amounts of explosives, electricity, or kinetic