Widowmaker

The Widowmaker is a very high leveled Spiderant that you will encounter during the "A Bug Problem" quest. This enemy is very distinctive due to its dark blue/purple and green colour. Widowmaker first spawns after you take a Retching Seeps sample from a deposit in Rust Commons East, but will keep on respawning after the quest is completed whenever you are near her spawn point.

When Widowmaker spawns, the ground shudders and kicks up a dust cloud after which she emerges. She will drop several pieces of loot when killed but does not have hold any unique or special items.

Widowmaker got her name because she has killed every would-be exterminator that ever attempted to kill her. (From the official Borderlands guide)

Attacks

 * Long ranged attack - Widowmaker will fire balls of white liquid from its abdomen, this is very similar to all spiderants.
 * Close range stomp - This spiderant will stomp with both front legs if you are very close to it, creating a sonic boom that damages you and sends you a couple feet back.
 * Burrowing - Widowmaker has the ability to burrow which is very uncommon if not non-exsitant with other spiderants.
 * Corrosive Stomp - Widowmaker will look like its doing the usual close range stomp but when it hits the ground it will fire a corrosive ring of rays at you.

Strategy
Like all spiderants, the Windowmaker has a weak abdomen; this is where you can score critical hits. The easiest way to attack this area is to flank her in order to hit her abdomen.

As with all spiderants, shooting her armored head causes her to flinch. This stops movement and causes the spiderant to clumsily turn and expose her abdomen for a few seconds before she recovers.

Unlike other spiderants, Widowmaker will not try to hit you with its front legs. It is therefore a good method to get close, although the stomp attack will make this difficult. Dodging her shock wave while moving forward is key. One strategy is to position a tall terrain obstacle between you and Widowmaker while staying as close as possible to her. This will cause her to try to continually get closer to you but without jumping, or to shoot at you despite the obstacle blocking her projectiles and not hitting you. A swiftly moving player can thus run back and fourth from each side of the obstacle to shoot her abdomen, ducking back to keep the obstacle between the two of you.

Alternatively, you can also just run over her with a car, though this will earn you less XP. At higher levels (i.e. on 2nd or 3rd playthroughs) you also run the risk of destroying your vehicle in an attempt to run her over at full health, leaving you in a vulnerable position.

Trivia
The name 'Widowmaker' is possibly a reference to a boss in the game 'Resistance: Fall of man', who has a very similar body shape to Spiderants, and has the same name.

The name might also come from the Black Widow, an extremely venomous spider.