Drain Deimos

Drain Deimos was a type of flea which had become infected with the t-Virus. With the infection they grew hundreds of times in size and their physical characteristics had been altered enormously.

Physically they resemble a muscular arthropod with sharp pincers and have the ability to implant thousands of parasites into a victim by clamping onto their heads and forcing them down their throat. They could only employ a similar technique to feed on a victim, sucking large amounts of their blood and causing massive organ failure and brain damage, while at the same time passing on a t-Virus infection.

They gathered in small groups and liked to hide along walls or suspended along ceilings in order to hunt their prey. However, they were only ever seen in an underground maintenance area in Raccoon City during a t-Virus outbreak, so it's clear that a very specific order of circumstances are required for them to exist.

It's worth noting that their increase in size is remarkable and Umbrella would have researched them heavily if they had the chance, but all examples of Drain Deimos were destroyed when the entire city was levelled by an explosion.