- "Perhaps a more sophisticated version of the Imposter species? "
- —T'Phai on the Infiltrator Bug.[src]
This subspecies appears to be a further evolved strain of the deadly Imposter bugs and served as a method through which the Arachnid army could infiltrate enemy populations. Notable facts about the Infiltrators is that they could switch between their true Arachnid form and that of their Human form. In their native shape, they shared many of the physiological features of the Warrior Bug though their head was somewhat different. Typically, they remained in their human disguise but when they were in combat situations they tended to morph into their bug form.
In the latter, they appeared completely human to the point that they possessed human DNA and could even pass for humans on a cursory scan. Though capable of fooling others of their origin, this subspecies had a number of traits that revealed their true origin. The first is that each member tended to look exactly similar and the second fact about them is that they had limited speech capacity which meant that they often repeated the same phrase to other humans. Despite these possible disadvantages, the Infiltrator is intelligent enough to make use of firearms and using them within their human guise. In addition, they are also equally capable of driving vehicles and taking part in advanced tactics such as using sniping positions.
Another trait amongst these Arachnids is that they are equipped with the same psychic shielding as the Queen Bug. This allows them to hide amongst an enemy population without being detected by psychics.
The creation of the Infiltrator Bug came sometime after the events of the Klendathu Campaign and the supposed death of the Queen Bug over Earth. At the time, it was believed that the matriarch of the Arachnid race was dead and thus the war was over leading to an end of hostilities with Mobile Infantry units pulling out for other duties. However, psychic trooper Carl Jenkins recieved a mental imprint suggesting that the Queen was in fact alive and somewhere on Earth though his views were dismissed by SICON as there was nothing to suggest that the Queen Bug survived. Despite this, Jenkins managed to convince Sergeant Johnny Rico to listen to him and together with the Roughnecks they investigated a town where an unknown heat signature was detected. Arriving in the settlement, Jenkins reported that he sensed Bugs everywhere but all they saw were Humans. A curious fact about the inhabitants was that they all had similar facial features and repeated the same phrases over and over again. This brought about suspicion amongst the Roughnecks who were eventually attacked by the armed towns people that brought handguns to bear on them. At first, Jean Razak believed they were civilians and stopped his troopers from harming them.
A single Infiltrator was tranquilized and captured by the Roughnecks who took it aboard their dropship. Once there, they did not manage to determine its true nature until it transformed and attacked. Using shock sticks against it, they managed to stun it and further drug it into a sleep-like state where "Doc" discovered the disturbing truth about these creatures. It was determined that they possessed both human and Arachnid DNA similar to the Zander Bug allowing it to masquerade themselves as humans without their neighbours learning of their true origins. Carl Jenkins later determined that they made use of psychic shielding to hide their activity from psychics. With it being knocked out, Jenkins learnt from the Infiltrators weakened mind that they were being used to target fifty locations on Earth in order to sabotage them as part of a new offensive by the Arachnids.