Helob is a powerful Spiderant encountered in the mission, A Bug Problem. Helob first spawns after a sulphur sample is removed from a deposit in Rust Common East, and will keep on respawning after the mission is completed whenever someone passes through its spawn point.
One of the deadliest spiderants, Helob has learned a leap attack that allows him to catch low-flying rakk and more effectively ambush prey on the ground. Reports from settlers on the incredible leaping ability of Helob differ radically. They range from "10 feet" to "all the way into outer space". Its actual jumping ability is generally believed to be much closer to the lower end of this reported spectrum, though no specific data exists to confirm any hypothesis at this time. (From the official Borderlands Guide)
Helob can be found in the lowest and most right corner of Rust Commons East, southeast of The CauldronFast Travel. It is a gentle hill, with several other Spiderants, and two tents, both with munitions boxes and money containers.
The name Helob is likely inspired by the giant spider Shelob in J.R.R Tolkien's Lord of The Rings. Lob is from the Old English word loppe, meaning spider; Tolkien admitted in a letter to his son that Shelob was "only 'she + lob'." Helob is presumed to be male.