You most likely dont have insects, but a bird. Depending on where you live, you either have a Yellow Bellied Sapsucker, or their cousin, the Red Bellied Sapsucker.
Sapsuckers make rows of horizontal holes (if given enough time) and feed off both the sap that is produced from the holes, and the bugs that get stuck in the sap.
Unfortunately it doesn't look too good, but they won't kill the tree. And, they are kinda neat birds to have around.
Here is a description of what they do...
The four species of sapsuckers all drill small sap wells in regularly spaced rows or columns on tree trunks. They eat the exposed inner bark and cambium and drink the sugary sap that flows from these pits. Yellow-bellied Sapsuckers have been found to tap over 250 species of trees and vines. Sap composes up to 20 percent of their diet and is especially important in late summer and autumn, or any time when other food sources are scarce. During the breeding season, they forage in the manner of typical woodpeckers, flaking off bark chips or excavating insects in dead wood. They also sally from perches to catch flying insects in the manner of flycatchers. In early spring, buds are eaten, and from October to February, fruit and berries are significant.
Yellow-bellied Sapsuckers can be found breeding across Canada east of the Rockies to southern Labrador and Newfoundland south to the northern United States from North Dakota to New York and Connecticut and south through the Appalachians to northwest Georgia. During winter, these migratory woodpeckers are common only where the temperatures seldom fall below 32 degrees Fahrenheit. Almost all leave the summer range and winter in the southeastern United States, the West Indies, and in the middle and high altitudes of Central America as far south as Panama. Yellow-bellied Sapsuckers are among the most highly migratory woodpeckers, and the only northern woodpecker to winter so far south.
Hope this answers your question.