The Old World ant cricket Myrmecophilus americanus Saussure (Orthoptera, Myrmecophilidae) inhabits nests of the Old World tramp ant Paratrechina longicornis (Latreille) (Hymenoptera: Formicidae). Paratrechina longicornis has spread worldwide through human commerce, whereas M. americanus has been reported from sites in Asia, Oceania, South America, the West Indies, and the Mediterranean region. Here, we report the first North American records of M. americanus, all from peninsular Florida and the Florida Keys. In addition to older unpublished records of M. americanus from Archbold Biological Station (N 27.2°) and Gainesville (N 29.7°), we collected M. americanus from 5 of 13 P. longicornis nests surveyed in southernmost Florida (N 24.5–26.0°), but only from 1 of 20 P. longicornis nests surveyed further north (N 26.5–27.3°) in Florida. Although P. longicornis is common throughout most of Florida south of N 30°, its symbiont M. americanus appears to be common only in southernmost Florida. If climate limits populations of M. americanus in northern Florida, then it is likely that the higher latitude records reported as M. americanus from subtropical semi-arid Mediterranean sites (Egypt, Libya, and Israel; N 30–32°) are actually misidentifications of one or more distinct species, possibly Myrmecophilus cottami Chopard and/or Myrmecophilus surcoufi Chopard.
Ant crickets (Orthoptera, Myrmecophilidae, Myrmecophilus spp.) (Fig. 1) are small wingless symbionts that live in and around ant nests. Myrmecophilus crickets are kleptoparasitic, feeding on the ants' food within the ant nests and inducing adult ant workers to regurgitate liquid food (Henderson & Akre 1986). When detected, Myrmecophilus crickets are treated as unwelcome guests by their host ant colonies, and the ants kill and eat captured crickets. Myrmecophilus crickets can chemically camouflage themselves, matching their cuticular hydrocarbon profile to that of their host ant species, apparently using cuticular hydrocarbons they scrape from both live and dead ants (Akino et al. 1996). Some Myrmecophilus crickets are generalists with respect to host ant, whereas others are very host specific (Komatsu et al. 2009). For example, Hebard (1920) listed 8–13 known host ant species for each native North American Myrmecophilus species. In contrast, most if not all host records for Myrmecophilus americanus Saussure are a single ant species: the longhorn crazy ant, Paratrechina longicornis (Latrielle) (Wetterer & Hugel 2008).
Saussure (1877) described M. americanus from Colombia, South America. Myrmecophilus americanus can be distinguished from most Myrmecophilus species by the combination of the following characters: Size small: males: 1.6–2.0 mm, females 1.8–2.5 mm (range mostly due to dry versus liquid preservation). General coloration: dark brown with a lighter stripe on the posterior half of mesonotum, and pronotum without a pair of lighter spots. Hind tibia has three inner and three outer apical spurs and one outer and three inner subapical spurs. Hind basitarsus usually has (in addition to two apical spurs) two dorsal spurs variable in size (one proximal and one distal); sometimes the distal or both dorsal spurs are lacking. The sclerified part of ovipositor dorsal valves is ladle–shaped. A few Myrmecophilus species share some of the above mentioned characters:
Myrmecophilus surcoufi Chopard, M. cottami Chopard, and M. brevipalpis Chopard are very similar to M. americanus. Myrmecophilus surcoufi and M. americanus differ in coloration (uniform in M. surcoufi, mesonotum with a light stripe in M. americanus); M. cottami and M. americanus differ by the hind basitarsus armature (a single dorsal spur in the middle in M. cottami); M. brevipalpis and M. americanus differ by the shape of maxillary palpi (fifth joint short and thick in M. brevipalpis, long in M. americanus) and by length of hind tarsus (longer than hind tibia in M. brevipalpis, shorter than hind tibia in M. americanus).
Using a variety of evidence, Wetterer (2008) concluded that P. longicornis and M. americanus are both Old World species, apparently native to tropical Asia and Melanesia (and not native to the Americas as the name americanus might imply). Both species have spread broadly through human commerce (Wetterer 2008; Wetterer & Hugel 2008).
Almost all published records of M. americanus are from tropical locales below N 23° latitude, including sites in India, the western Indian Ocean (Madagascar, Seychelles, and Réunion), Oceania (Hawaii), and the Neotropics (Brazil, Colombia, and many West Indian islands) (Wetterer & Hugel 2008). The only published non-tropical records of M. americanus come from considerably higher latitudes in the Mediterranean region (Egypt, Libya, and Israel; N 30–32°; Wetterer & Hugel 2008).
Although there are no previously published North American records of M. americanus, Trager (1984; pers. comm.) apparently found this cricket in Gainesville, Florida (N 29.7°) “scurrying among a large swarm of Paratrechina longicornis that had just been flooded out of its nest by lawn sprinklers.” The cricket specimen was destroyed, but Trager (pers. comm.) is confident of its identification as M. americanus due to its distinctive light stripe, not found in any North American Myrmecophilus species. Trager (1984), however, mistakenly reported that the cricket was very likely Myrmecophila acervorum flavocincta Wasmann, based on Wheeler's (1910) misstatement that “M. flavocincta occurs with Plagiolepis longipes [= Anoplolepis gracilipes] and Prenolepis longicornis [= Paratrechina longicornis] and has been introduced into Brazil with the latter ant.” In fact, M. flavocincta has never been reported associated with P. longicornis; Wasmann (1894) described M. flavocincta from a nest of P. longipes (= A. gracilipes) in India. Instead, Wheeler (1910) incorrectly conflated under the name M. flavocincta, Wasmann's (1905) record of M. prenolepidis (= M. americanus) associated with P. longicornis in Pará, Brazil.
The oldest extant M. americanus specimens from North America that we found were collected by Mark Deyrup outside buildings at Archbold Biological Station near Lake Placid, Florida (N 27.181° W 81.352°; 1 Nov 1989, 1 May 1990, 8 Apr 1994, 23 May 1994, 15 Jan 1998, and 1 Jun 2000), all accompanying swarms of P. longicornis relocating their colonies after being disturbed (M. Deyrup, pers. comm.; SH confirmed identification).
Site Records of Myrmecophilus americanus Collected by Jkw from Paratrechina longicornis Nests in Florida. Geo-coordinates in Decimal Degrees N and W.
Between 2007 and 2012, JKW searched for M. americanus in Florida whenever encountering large, accessible P. longicornis nests under rocks, concrete blocks, wooden boards, or logs (n = 33 nests), preserving specimens in 99% ethanol (all identified by SH). JKW found M. americanus in 5 of 13 P. longicornis nests in southernmost Florida, from Key West to Hollywood (N 24.5–26.0°; Table 1), but only in 1 of 20 P. longicornis nests at more northerly sites in southeast Florida from Boynton Beach to Port Saint Lucie (N 26.5–27.3°).
Wetterer & Hugel (2008) reported that M. americanus was widespread and fairly common in P. longicornis nests on West Indian islands, found in 13 of 39 nests searched on 7 islands. Here, we found that M. americanus appears to be similarly common in P. longicornis nests of southernmost Florida (N 24.5–26.0°). Myrmecophilus americanus is apparently uncommon in P. longicornis nests at higher latitudes in Florida, though it may be locally abundant, e.g., at Archbold Biological Station (N 27.2°). If M. americanus is common only in the southernmost parts in Florida, this indicates that the populations of M. americanus in more northern parts of the state are limited by some factor other than host availability. It is possible that the crickets have simply not yet spread to many P. longicornis colonies in northern Florida. Alternatively, the crickets may have a narrower climatic tolerance than the ants.
If climate limits populations of M. americanus in northern Florida, then this suggests that the higher latitude records reported as ‘M. americanus’ from subtropical semi-arid Mediterranean sites (Egypt, Libya, and Israel; N 30–32°) are actually misidentifications of one or more distinct species, possibly Myrmecophilus cottami and/or Myrmecophilus surcoufi (Chopard 1919, 1922). Significantly, the only report of ‘M. americanus’ found associated with a host ant other than P. longicornis was from Egypt and originally identi- fied as M. cottami (Ebner 1956). Although Capra (1929) and Chopard (1968) designated M. cottami as a junior synonym of M. americanus, Otte (1994) and Massa (1998) rejected this synonymy and Maruyama (2004) included M. cottami on a checklist of Myrmecophilus species. SH tentatively considers M. cottami to be a valid species. If the Mediterranean specimens reported as M. americanus prove to be a distinct species, then the present records of M. americanus from Florida are the only subtropical records known for this otherwise tropical species.
We thank M. Wetterer for comments on this manuscript; J. Trager and M. Deyrup for unpublished information and records; B. Burnett for field assistance; the National Science Foundation (DES-0515648) and Florida Atlantic University for financial support.