TortAI Larval Key - Port Intercepts
The larval key treats 50 taxa (species, genera, or tribes) that are most commonly intercepted during quarantine surveys by the USDA at
U.S. ports of entry. It is important to note that this key is not designed to identify all exotic tortricid larvae.
All taxa are treated as targets, although some may be considered non-actionable. Taxa were selected by consulting
USDA identification specialists and the USDA PestID database. Larval targets are listed as "Port Interception Target - Larva" on the fact sheets.
The key assumes that the larvae are late instar and originated outside of the continental United States (species originating from Hawaii
are treated as exotic). Taxa can be restricted by origin (geographic location) and host, and many times this information is
necessary to obtain a successful determination. Identification is performed using a variety of morphological characters in conjuction with the origin
and host data. Specific instructions for the key are provided below.
Tips for examining larvae
Identifiers unfamiliar with tortricid larvae should consult MacKay (1959, 1962), Brown (1987), and Gilligan et al. (2008) for an overview of larval morphology
and techniques. Larval characters vary extensively, even in the same species, both between instars and in the same instar. Most of the characters
included here are based on late or last instar larvae, and early instars of many species may be impossible to identify. When examining
pinacula and setal number, be sure to look at both sides of the larva, as some specimens are asymmetrical. When an asymmetrical individual is found,
use the highest number of setae when navigating the keys. Preservation of larvae can obscure characters, and even freshly preserved specimens may discolor
and make many of the color or pattern characters in the keys useless. It is also possible for pieces to break off specimens preserved in alcohol, and occasionally setae
or the anal comb may be missing because of breakage. Any determination made with the tortricid larval key should be checked by an expert, and molecular
analysis may be required to confirm identity in many cases.
Larval key instructions
The adult key is navigated by clicking in a checkbox next to the feature state. Chosen features are displayed in the bottom left pane.
Choosing multiple states for color or pattern features functions as an "AND" statement (body color: green AND brown = greenish-brown). Choosing
multiple states for morphological features functions as an "OR" statement (anal comb: present OR absent). Remaining entities (taxa) are displayed
in the top right pane and eliminated entities are displayed in the bottom right pane. Because this key has several dependent features,
it may be helpful to reload the key if too many mistakes are made selecting features. The key can be reloaded by choosing "Restart" under the "Key" menu.
Use the "Best" function with caution! The keys will function more efficiently if you manually select characters that you are familiar with instead of
using "Best." The "Best" algorithm automatically calculates and selects the feature that would eliminate approximately half of the remaining entities. As
the keys are designed with several dependencies and many characters are unique to a small group of taxa, the "Best" function automatically skips many
important characters. Exclusive use of the "Best" function may not result in a successful identification.
1. Is the larva a tortricid?
Choose "Yes" if the specimen being keyed is a tortricid, or choose "Unsure" if you are not certain. Choosing "Yes" will automatically skip to #3 (below),
"Choose the larval origin." Choosing "Unsure" will automatically load several family level characters.
2. Family level characters
This option is only loaded if "Unsure" was selected in #1 (above). Select morphological characters here to determine if the specimen is a tortricid. Three
Lepidoptera superfamilies containing taxa that may be commonly confused with tortricids are included in the entity list. Two general categories are also included to
account for character states that do not fit with any specific entities. The next option (#3) will only appear if one or more tortricid species remains in the
entity list; if one of the other superfamilies or general categories is the only remaining entity, the key is completed and additional resources for larval
identification should be consulted.
3. Choose the larval origin
Select the geographic origin of the specimen you are trying to identify. If you do not know the origin or are unsure, select "Unknown;" however,
selecting "Unknown" may reduce your chances of a successful determination as host information will not be loaded. There are also no regular hosts
associated with larvae originating from Canada.
4. Hosts (origin)
This option will load if any origin other than "Canada" or "Unknown" is selected in #3 (above). Choose the particular host on which the larva was intercepted,
if this information is known. Choosing a host is optional, and choices here do not affect other characters in the key. DO NOT GUESS AT A HOST IF IT UNKNOWN OR NOT LISTED.
The host lists are the export products on which a particular tortricid species or group is commonly intercepted. In many cases, selecting a host will narrow the entity
list to one taxon (e.g. Africa: Capsicum = Thaumatotibia leucotreta). This does not mean that the single entity is the only larva found on this combination of
origin/host, but rather that it is the most likely choice. ALL ENTITIES THAT REMAIN AFTER CHOOSING A SPECIFIC HOST SHOULD BE CHECKED FOR MATCHING MORPHOLOGICAL CHARACTERS.
Choosing a host option is required to display the remaining features #5-8 (below).
All of the head features listed here are instar-dependent. The general color, markings, and mandible morphology can vary between instars, and all of the feature states
in this section are coded assuming a late or last instar larva.
The thorax includes several diagnostic structures, such as the prothoracic shield and the prothoracic prespiracular pinaculum. These features (especially the prespiracular
pinaculum shape) can be used to narrow the remaining taxa to several species groups. As with the head, markings and coloration on the legs and prothoracic shield change over
time, and they are coded here assuming a late instar larva.
The majority of diagnostic characters are found on the abdomen, and as many features should be scored here as possible. Markings, coloration, and crochet count may change
between instars, but the general chaetotaxy should remain fairly consistent. All taxa are scored assuming a late instar larva.
8. Feeding habits
If known, choose the feeding habits of the larva. This feature separates borers from external feeders.
The identifier is successful when the key is completed and one or more entities remain. In some cases it may be impossible to key a larva to a single entity, especially
if location and/or intercepted host information is not known. The identifier should consult the fact sheets for any remaining entities
(next to the species name) to determine if the description of the species is consistent with the specimen being examined. DNA data may be necessary to
provide or confirm identifications for many intercepted tortricid larvae.
The complete data matrix for the larval Port key is available here (PDF - opens in a new window): TortAI Port matrix.