BLACKARACHNIA

"My sting will be the last thing you feel." 

Affiliation: Decepticon
Function: Trickster

Alternate mode:
Giant Spider
Weapon: Cyber Venom, with contact, can absorb the special powers of her enemies.

First cartoon appearance: Transformers Transformers Animated Movie intro (in this form)

First Comic Appearance: IDW Comics, Transformers Animated, The Arrival #1

BLACKARACHNIA
(Voiced by Cree Summer)

BLACKARACHNIA is a freak among DECEPTICONS. Some time back, an encounter with the ALLSPARK caused her to fuse with an organic spider, turning her into a techno-organic hybrid of animal and machine. She despises this new form, especially on Earth, where her giant spider mode doesn’t exactly allow her to “blend.” BLACKARACHNIA will do anything to find a cure for her condition and doesn’t care who she has to step on to get it. Obviously the ALLSPARK and its Autobot protectors will play a big role in her schemes. 

Robot Mode Power: BLACKARACHNIA has multiple eyes and eight limbs – two of which are skinny, pincer-like “spider limbs” that jut from her back and arc over her shoulders. The pincer limbs can strike like scorpions’ tails, stunning prey with her venom, or spraying spider-like webs. She also has the ability to download and temporarily absorb other Cybertronians’ powers.

Vehicle Mode Appearance: BLACKARACHNIA has no vehicle mode appearance. Instead she changes into a giant techno-organic black widow spider. 

Character description from package "tech spec":  Blackarachnia started out as a promising young recruit at the Autobot Academy.  accidentally abandoned on a hostile alien world by her teammates, she did the only thing she could --merged with the organic giant spiders that sawrmed the caves in which she was trapped.  Emerging as a technorganic mutant, she vowed revenge on the Autobots that had left her behind, and joined with the Decepticons in their war of conquest. 

Galactic Powers and Abilities:
> Generates organic webbing stronger than steel.
> Mech-venom paralyzes mechanical victims.
> Feeds on raw Energon siphoned from machines. 

Other appearances: Work with me here!  Tarantulas was the (evil)  mad scientist of Beast Wars, couldn't one suppose that upon finding a Maximal stasis pod, he extinguished the Maximal spark within and "resurrected" Blackarachnia, the same individual whose origin was told in Transformers Animated?  Heck the season 3 episode, "Predacons Rising" could very well tell the origin of the Predacons.  What if it turns out that Animated Blackarachnia is a founding member!  Is it too much to suppose that Tarantualas could have procured her spark after a fatal battle...  Only time will tell if my theory could be so.  

Regardless of how you choose to see it, here are a list of other Blackarachnia characters from TF mythology: 
1996: Beast Wars original
1998: McDonald's Happy Meal Transmetal
1999: Transmetal 2 Blackarachnia
2000: Beast Wars Blackarachnia

Bibliography of significant appearances: Blackarachnia is the only Transformer in the Animated movie introduction with the same alternate mode as she has once she arrives on Earth.  She was heavily featured in episode 6 Along Came a Spider and 23 Black Friday