Some issues with the original design include the following:
1) Actual depiction of the pests is not attractive or necessary
2) There are too many random elements in the graphic, much of which seems to lack purpose
3) It lacks versatility as its an unusual shape and the details get lost when the logo is applied at small sizes
4) There is a readability problem as the 'v' of Dever, morphs into something else. Someone who is not familiar with the company may even read 'deer' instead.
The design direction for the update was based on the premise that people do not like pests and want to see them swiftly eliminated. As a result, the logo has a certain military/aggressive feel to it, thereby tapping into the subconscious feelings of their customers. In addition, all other problems are taken care of:
1) There is only an allusion to pests - no actual depiction
2) Every element of the design is purposeful
3) It is highly versatile and simplified, working great at all sizes
4) No more readability issues.