Why so complicated?
If the storyline of a city being attacked at the start of all this happens to be actual at this dev, there is a quite easy way to modify the text to the bloodspiders.
The bloodspiders were most likely to be part of the initial alien attack on Mumbai, so these robots had been seen by humans (even if the player himself didn't encounter them). So refer to this attack. Tell that there were these so called bloodspiders, mechanical terror units, involved in the first invasion and that they were vulnerable against overcharging (e.g. in contact to a high voltage power line), so the chances are quite good the stun rod may overcharge and temporaly disable their circuits, too. (All that has to be done is giving the player the idea, it could be effective to use the stun rod on a robot, and sugguesting this might work is enough to plant that idea).
