Problem: WMS features cannot be identified
WMS service sublayers are not listed as layers that can be identified in the dropdown list of the Identify Results dialog.
Not all WMS features can be identified. Only WMS service features from layers that support the <GetFeatureInfo> tag can be identified. A WMS service may only support the GetFeatureInfo operation on specific layers in the service. It is not required that the WMS service support <GetFeatureInfo>.
Solution or Workaround
This is a known limitation. It is up to the WMS service to determine which WMS layers, if any, you can query. ArcMap will only list the WMS layers support <GetFeatureInfo> in the layers dropdown list in the Identify Results dialog. You can also look at the WMS service capabilities file to see what the service supports.
<a href='http://support.esri.com/en/knowledgebase/techarticles/detail/27948' target='_blank'>How To: View the WMS service capabilities</a> If you do not see the <GetFeatureInfo> tag, the WMS layer cannot be queried.