Kunal, sorry, been busy. You need to add the other layers as feature layers as well. The code below adds them all in order:
var featureLayer0 = new esri.layers.FeatureLayer("http://geoapps.rc.rit.edu/ArcGIS/rest/services/eInvertebrates2/MapServer/0",{
mode: esri.layers.FeatureLayer.MODE_SELECTION,
outFields: ["*"],
infoTemplate:template
});
map.addLayer(featureLayer0);
var featureLayer1 = new esri.layers.FeatureLayer("http://geoapps.rc.rit.edu/ArcGIS/rest/services/eInvertebrates2/MapServer/1",{
mode: esri.layers.FeatureLayer.MODE_SELECTION,
outFields: ["*"],
infoTemplate:template
});
map.addLayer(featureLayer1);
var featureLayer2 = new esri.layers.FeatureLayer("http://geoapps.rc.rit.edu/ArcGIS/rest/services/eInvertebrates2/MapServer/2",{
mode: esri.layers.FeatureLayer.MODE_SELECTION,
outFields: ["*"],
infoTemplate:template
});
map.addLayer(featureLayer2);
var featureLayer3 = new esri.layers.FeatureLayer("http://geoapps.rc.rit.edu/ArcGIS/rest/services/eInvertebrates2/MapServer/3",{
mode: esri.layers.FeatureLayer.MODE_SELECTION,
outFields: ["*"],
infoTemplate:template
});
map.addLayer(featureLayer3);
Now, when you click on each point it will show a popup. If there are coincident points, the API will choose the point that sits on the top and show the information for that. If you just want to show information for anywhere a user clicks then you should use a query task. This does not rely on feature layers. Let me know how you go.