A note of caution
It is important to note that unless the specimen you are trying to identify was collected at a port of entry, a disturbed habitat with a limited native ant fauna, or a Pacific Island there is a strong likelihood that the species to which it belongs is not in the key. If you believe the species is non-native and you use the key for identification, make sure to check your determination against the specimen images and read the corresponding species page. If you want assistance with the identification, or want to confirm your determination, please post a message in the forum.
The taxonomic scope of the Lucid key includes ants from across the globe that are considered invasive, introduced, or commonly intercepted. The current version of the key treats the worker castes of approximately 115 species, 42 genera and 8 subfamilies. The inclusion of species is based on literature records, specimen records, and reported observations. Pest ants that have not established populations outside of their native ranges are not currently included in the species key. As noted above, native ants are not included in the key. Two exceptions to this is are Nylanderia terricola, which has a worker caste nearly indistinguishable from the introduced Nylanderia vividula, and Solenopsis xyloni which is similar enough to highly invasive Solenopsis species as to warrant its inclusion.
For genera such as Cephalotes and Formica, which are commonly transported but are not known to include any invasive or introduced species, the key terminates at the genus level (e.g. "Cephalotes spp." and Formica spp."). There are also cases, such as Ochetellus, where a complex of closely taxa includes one or perhaps several introduced species, but the taxonomy is too poorly understood to confidently apply a species name. In these cases, the key terminates in a species complex (e.g. Ochetellus glaber complex"). There are several species that are either undescribed or whose names have not yet been determined (e.g. Tetramorium caespitum_cf and Brachymyrmex JAM-001). Lastly, Anergates atratulus is not included in the key, as the species is a highly derived inquiline and lacks a worker caste.
The geographic scope of the Lucid key is currently limited to the introduced and commonly intercepted ants of the United States, including Hawaii. The effective geographic coverage of the key is actually much greater, however. Most of the species introduced to the United States have also established elsewhere in the world. For example, the key covers all the ant species introduced to North America and most Pacific Islands. There is also a strong overlap with the Neotropics, Europe and Australia. The key is likely to be more limited if used in the Old World tropics (including Asia, Africa and the Malagasy region) and New Zealand. The former regions are likely to harbor species that have been introduced from elsewhere in the Old World tropics, but that have not established in the New World. New Zealand harbors many species that have been introduced from Australia, but have not established elsewhere in the Pacific or the New World.
The key also omits species that are native to the continental United States but were intercepted or have become established in a state outside of their native range. Records show that there are many cases of interstate interceptions, and while inclusion of these species would be of great benefit to inspectors, it would require a significant update to the current version of the key.