Canoptek Spyder
Canoptek Spyders and Tomb Spyders are Necron constructs used to watch over and tend the sleeping Necron Tomb Worlds like a glorified house maid. These Spyders despite being glorified house maids are pretty formidable defenders and are great at driving those pesky kids off their masters lawn yard. They are often armed with hives of Scarabs in addition to self-repair backup systems.They are also capable of directing Wraiths against any who are brave/stupid enough to venture into a Necron Tomb. However the most dreaded annoying aspect of Tomb Spyders is their ability to quickly repair other Necron Warriors on the field of battle. This means that if your Necron lord for some reason, doesn't have the re-animation protocol, than you can use the Spyders as a back up just in case. Spyders also possess the ability to rapidly manufacture swarms of diminutive drone-like constructs in vast, shimmering clouds if they want to annoy the enemy.
While Canoptek and Tomb Spyders are different varieties of the same construct. Let's not kid ourselves when we know that the Canoptek is a revamped Tomb Spyder and that Games Workshop is too lazy to be bothered to make two different rules for two types of Spyders.