I tried adding a slash to the end of the URL, after the 2, but still could not achieve the desired result.
Is it possible to add individual layers from these map services, or must I move the layers into their own "MapServer" area? Or what can I add after the layer number in the URL in order to ensure that only that layer is added?
It is possible. However, my question is why do you want to do this?
In looking at your map service, it seems like you have several layers of biological data, however, they are somewhat disparate in nature. Another approach would be to author more than one map service and put those layers in it that you're likely to use together to "mash-up" on the web. For example, you might put your seabird layers in one map service, the bear sightings in another and the public oyster areas in a third.
Having said this, here's the answer to your question. From the Add menu on the map, choose the Add layer from Web option. Choose the ArcGIS Server Web Service option and enter the URL you specify below ...MapServer/2. However, adding a layer in this fashion will probably lead to other questions that will require you to understand more about the ArcGIS Online system, ArcGIS Server, and web browsers.
ArcGIS Server map services typically return images (either cached or dynamic) to a client (like ArcGIS.com map viewer). All layers are drawn based on what the service author defined in the map the service was created from. The server takes a snapshot of the desired map extent and returns this image to the client, and the client displays it.
When you add an individual layer from a map service to the map viewer, you essentially bypass the image creation. Instead, the map viewer sends a query for the actual data of the layer and draws the layer's features on the client, in this case the browser. Most map services (yours included) use the default query limit of 1000 features. So, you won't be able to get all the features you might expect. And in reality, you really don't want increase the query limit, as it would start to put a load on your server. Also, it's a lot of data to be passed across the wire. It can help to define scale visibility limits in the map viewer. Also, you just get the geometry of the features in the query, so you have to set up the drawing of the features on the client as well (note that both of these are available on the content menu of the layer in the TOC of the map viewer).
OK, so that's what the server and map viewer are doing. Now you have to consider the web browser. The web browser can only handle drawing so many features. Really, as you start to get over 1000 polygons, things will probably slow down--especially in IE. And if you want to add 2 or 3 layers, you could be talking about drawing 2000-3000 polygons. It probably won't perform well. Here's a recent ArcGIS Server blog post that discusses this.
In looking at your map service, it seems like you have several layers of biological data, however, they are somewhat disparate in nature. Another approach would be to author more than one map service and put those layers in it that you're likely to use together to "mash-up" on the web. For example, you might put your seabird layers in one map service, the bear sightings in another and the public oyster areas in a third.
That's what I wanted to avoid. I have a number of other map services with multiple disparate layers. I don't want to add these services and have all those layers mashed up together, but it is going to be a hassle for us to create different map services for the different topics.
I understand I can add the individual layers from the map services into the map, but how can I make it so that people could search for that data? I would like for people to be able to search "Louisiana bear" and have the data pop up for bears only, not for oysters, seabirds, etc also. That is why I wanted to be able to add the layers directly into the "My Content" area, not simply into the online map viewer.
