When you see the Lumeta "L" favicon displayed on a map with attached hosts, it means that the device is scanning the local subnet via Path Discovery and has found those hosts at the next hop.
Question: When a zone contains multiple collectors, which of those collectors display on the map?
Answer: None. Zone collectors do not display on Lumeta maps. However, the interfaces to collectors do display on maps. A collector interface is located on a Command Center or a Scout. In either case, the map icon is the Lumeta "L" favicon.
Question: What does it mean when you see a Lumeta device displayed on a map with attached hosts?
Answer: It means that the device is scanning the local subnet via Path Discovery and has found those hosts at the next hop.
Question: How does Lumeta know when devices should "hang off" a device on a zone map?
Answer: When Path Discovery is enabled, a select set of information is also gathered via SNMP. The information gathered includes system, interface, route table, and ARP table data. This data enables Lumeta to decide that there are devices attached to this device (presumably through Layer 2 MIBs).