Given the following context:

Dr. Robert "Rack" Hansen, a veterinarian in rural Verde Valley, Arizona, receives an urgent call from a local farmer, Walter Colby. Colby is upset because his prize calf has become sick for no apparent reason, and the animal is brought in to Hansen's laboratory. Hansen examines the calf, which dies shortly afterward. Hansen tells Colby he cannot explain what made the animal so ill so quickly, but takes samples of the calf's blood to a university lab in Flagstaff.
A few days later, Diane Ashley, an arachnologist, arrives looking for Hansen. Ashley tells Hansen that the calf was killed by a massive dose of spider venom, which Hansen greets with skepticism and disbelief. Undaunted, Ashley tells him the problem is serious and that she wishes to examine the animal's carcass and the area where it became sick. Hansen escorts Ashley to Colby's farm; and moments after they arrive, Colby's wife, Birch, discovers their dog is also mysteriously dead. Ashley performs a quick chemical test on the dog's carcass and concludes that like the calf, it died from a massive injection of spider venom. Hansen is incredulous, until Colby states that he recently found a massive "spider hill" on a back section of his farmland. He takes Hansen and Ashley to the hill, which is covered with tarantulas. Ashley theorizes that the tarantulas are converging together due to the heavy use of pesticides, which are eradicating their natural food supply. In order to survive, the spiders are joining forces to attack and eat larger animals--and humans.

answer the following question:

What is the full name of the person who recently found a massive "spider hill"? 

Walter Colby