Strumigenys rogeri

A tramp species that can be abundant in moist habitats.

Identification
See the description section below.

Distribution
This taxon was described from Antilles. It is also found in New Caledonia, Philippines, Mexico, Honduras, Costa Rica, Canada, United States, Cuba, Haiti, Dominican Republic, Puerto Rico, Burundi, Comoros, Seychelles, Réunion, Mayotte, Mauritius, Madagascar, Angola, Cameroon, Gabon, Ivory Coast, Ghana, Nigeria, Indonesia, Malaysia, Fiji, Solomon Islands, Vanuatu, Samoa, Tonga, Niue, Saint Lucia, Barbados, Marshall Islands, Micronesia (Federated States of), Northern Mariana Islands and Borneo.

Biology
Brown (1954):

"I am fortunate also in having important notes on the biology of S. rogeri made by E. O. Wilson during his stay in Cuba in the summer of 1953.

Wilson took his observation colony at San Vicente, Pinar del Rio, Cuba, from a small nest under a rotten limb lying on well shaded ground. The galleries extended into the wood itself. Transferred to a small plaster observation nest, the workers readily captured numbers of entomobryoid collembolans proffered; campodeids up to four times the length of the ants were also always accepted and, like the entomobryoids, were fed to the larvae. Also observed to be chewed by the larvae after capture were a small psocopteran, a small ichneumonid wasp, and a small, injured embiopteran that had previously been ignored by a colony of Smithistruma nigrescens (= Strumigenys nigrescens) Wheeler. A symphylan and a pseudoscorpion, one each, were accepted and eaten by the larvae, but only after lengthy contact with the ants. Other specimens of these last two groups seem to have been refused by the larvae after capture on some occasions. A small polydesmid millipede was also captured, but soon rejected by larvae and workers. Consistently avoided or ignored when offered in the intimate confines of the observation nest were mites, nasute and other termites, small isopods, poduroid collembolans, adult staphylinid and sylvanid beetles of small size, a small campodeiform beetle larva, and dead mosquitoes, though the beetles mentioned disappeared from the nest and may possibly have been eaten.. Drosophila adults werc caught by the adults, but later discarded.

Entomobryoid collembolans seemed to be the usual and preferred prey fed to the larvae, although campodeids were never refused. In feeding habits, therefore, S. rogeri follows the generic habit of collembolan predation but, like some other widespread dacetine species, it will also accept a variety of other small arthropods, particularly campodeids, when available. In hunting, or when disturbed, the workers and females open the mandibles to slightly more than 180 degrees."

Florida (USA)
Deyrup (1997) reports this species is often the dominant dacetine ant in moist hammocks and swamp forest.

Clouse (1999) - Found Strumigenys rogeri to be common in wet areas of Everglades National Park and occurring in high densities along marshy trails on the Eastern Florida coast.

Deyrup et al. (2000) - This species is the common dacetine in bayheads, baygalls, and other swamp forest habitats in south and central Florida. Found as far north as northern Orange County. First published Florida record: Deyrup and Trager 1984; earlier specimens: 1965.

Puerto Rico
Wheeler (1908): Numerous workers and females taken from several colonies nesting under stones in a nearly dry stream bottom behind the Coamo baths. The rediscovery of the female of this species shows that Emery was right in his contention that Roger had described two very different species under the name of Pyrmaica gundlachi (=Strumigenys gundlachi). The females among my specimens agree perfectly with Roger's description and figure (Taf. I, .Fig. 18a).

Morphology
Gronenberg (1996), the Strumigenys sp. shown in image may be rogeri or another member of the rogeri-complex'':

"Abstract: Ants of three different subfamilies, among them the tribe Dacetini, have evolved very fast snapping mandibles called trap-jaws. The two dacetine genera examined, the large Daceton and the small Strumigenys, employ the same mechanism for their mandible strike. Video analysis reveals that, in Strumigenys sp., the strike takes less than 2.5 ms. It is released within 5 ms by contact of trigger hairs on the labrum. The ants employ a catapult mechanism to generate such a fast movement. Before the strike, the mandibles are opened wide and locked in the open position by the labrum, which functions as a latch. They stay open even when the large slow closer muscles contract. Upon trigger hair stimulation, the labrum is pulled backwards by a small, fast trigger muscle. The mandibles are thus freed from the catch and close rapidly. This reflex is controlled by giant sensory and motor neurons in the labral neuromere that are probably monosynaptically coupled. The short latency of the reflex thus results from the combination of a catapult mechanism, fast trigger muscles, high neuronal conduction velocities and small synaptic delays. Comparison with the trap-jaw mechanism of the ant genus Odontomachus reveals a remarkable example of convergent evolution."

and within the paper is this more detailed description:

"In the foraging arena, Strumigenys sp. generally walk around slowly with closed mandibles. The scapes of their antennae are held perpendicularly to the body’s long axis while the flagella point forwards. These small ants (body length without mandibles, 1.2–1.5 mm) have to approach very close to the potential prey in order to initiate prey-capture behaviour. In the present experiments, most collembolan prey was smaller than the ants, but Strumigenys sp. also attacked prey of about their own size.

Upon brief antennal contact with the prey, the mandibles are opened completely (the angle between the mandibles is approximately 220 °) and the ants move more slowly so as to avoid any disturbance of the prey. At the same time, they perform swaying search movements with the head and body in order to re-establish antennal contact with the prey (see detailed description by Dejean, 1986). Vision does not seem to be involved in this apparently chemosensory searching behaviour. In the absence of antennal contact, the springtails can literally step on the ants without releasing prey-catching behaviour. If, however, the collembolan’s position is established by another antennal contact, Strumigenys sp. stalks the springtail until the forward-pointing trigger hairs on the labrum contact the prey. The mandibles snap shut immediately after the prey touches the trigger hairs. As in other trap-jaw ants, the trigger hairs thus act as a rangefinder and trigger the strike when the prey is in the correct position between the mandibles. The mandible strike occurs within 2.5 ms. However, in several cases, prey catching was not successful: large collembolans may struggle free or the strike may be triggered by a leg or antenna of the springtail. In this case, the ant clasps a limb of the prey rather than its body and the springtail may then be able to perform an escape jump. After a successful strike, when the prey is penetrated and firmly held by the mandibles, the ant immediately bends the gaster forwards and stings the prey to prevent further struggling.

The latency of the entire trap-jaw reflex (including trigger hair contact and mandible strike) could not accurately be assessed from the high-frequency video recordings because the hairs are too small to be resolved by the system. Only two video sequences allowed an approximation of the reflex latency (judging from the distance between the ant’s head and the springtail). In both cases, the supposed trigger hair contact and the mandible strike occurred within two video frames (within 5 ms)."

Nomenclature

 *  rogeri. Strumigenys rogeri Emery, 1890b: 68, pl. 7, fig. 6 (w.) ANTILLES. Forel, 1893g: 378 (q.). Senior synonym of incisa: Donisthorpe, 1915d: 341; of sulfurea: Brown, 1954k: 20. See also: Bolton, 1983: 387; Bolton, 2000: 604.
 * incisa. Strumigenys incisa Godfrey, 1907: 102 (w.) GREAT BRITAIN. Junior synonym of rogeri: Donisthorpe, 1915d: 341.
 * sulfurea. Strumigenys sulfurea Santschi, 1915c: 261 (w.) GABON. Junior synonym of rogeri: Brown, 1954k: 20.

Worker
Bolton (2000) - TL 2.3 - 2.8, HL 0.58 - 0 .74, HW 0.42 - 0.52, CI 69 - 75, ML 0.30 - 0.40, MI 51 - 58, SL 0.36 - 0.46, SI 82 - 89, PW 0.27 - 0.32, AL 0.56 - 0.68 (45 measured). Characters of rogeri-complex''. Mandibles relatively stout and more or less straight through most of their length; not obviously bowed outwards. On each mandible proximal preapical tooth stout and usually no longer than maximum width of mandible, usually slightly shorter. Distal preapical tooth shorter than proximal but nearly as stout. On right mandible distal preapical tooth slightly longer and thicker than on left mandible; not completely concealed by left apicodorsal tooth at full closure.

Type Material
Bolton (2000):

Holotype worker, ST THOMAS I. (West Indies) [examined].

Strumigenys incisa Godfrey, 1907: 102 [attributed to Forel]. Syntype workers, GREAT BRITAIN: Scotland, Edinburgh, hothouse in Royal Botanic Garden, 10.vi.1904 (R. Godfrey) [examined].

Strumigenys sulfurea Santschi, 1915: 261. Syntype workers, GABON: Samkita (F. Faure) [examined].

Additional References

 * Brown, W. L., Jr. 1954. The ant genus Strumigenys Fred. Smith in the Ethiopian and Malagasy regions. Bull. Mus. Comp. Zool. 112:1-34.


 * Clouse, R. 1999: Leaf-litter inhabitants of a Brazilian pepper stand in Everglades National Park. Florida Entomologist 82: 388-403.


 * Deyrup, M. 1997. Dacetine ants of the Bahamas (Hymenoptera: Formicidae). Bahamas J. Sci. 5:2-6.


 * Deyrup, M., Davis, L. and Cover, S. 2000: Exotic ants in Florida. Transactions of the American Entomological Society 126: 293-326.


 * Gronenberg, W. 1996. The trap-jaw mechanism in the dacetine ants Daceton armigerum and Strumigenys sp. Journal of Experimental Biology (Cambridge). 199:2021-2033.


 * Wetterer, J.K. 2012. Worldwide spread of Roger's dacetine ant, Strumigenys rogeri (Hymenoptera: Formicidae). Myrmecological News 16:1-6.


 * Wheeler, W. M. 1908a. The ants of Porto Rico and the Virgin Islands. Bull. Am. Mus. Nat. Hist. 24: 117-158.