A new species of termite, Macuxitermes colombicus Postle & Scheffrahn is described from soldiers and workers collected from Departamento Magdalena, Colombia. The soldier of M. colombicus differs from its lone congener in having no protuberances on the head capsule.

Isoptera , Termitidae , Syntermitinae , Macuxitermes colombicus , Colombia, new species, taxonomy

The Neotropical subfamily Syntermitinae (Isoptera: Termitidae)—“the mandibulate nasutes”—is composed of 18 genera whose distribution ranges from southern Mexico to northern Argentina. The most diagnostic character of the subfamily is, as the name suggests, soldiers that possess a nasus in addition to well-developed mandibles. The component genera vary widely in the length of the nasus, with Syntermes spp. and Labiotermes spp. having the shortest and some Rhynchotermes spp. the longest nasus relative to head capsule proportions (Constantino and Carvalho 2011, Rocha et al. 2011, Fontes 1985), and two genera (Macuxitermes and Rhynchotermes) have species with major and minor soldiers; nevertheless, the monophyly of the subfamily is retained throughout (Inward et al. 2007, Noirot 2001).

Within the Syntermitinae, the three monotypic genera Macuxitermes, Noirotitermes, and Acangaobitermes form a small monophyletic group (Rocha et al. 2012). Based on original descriptions, this conclusion may seem unlikely. The soldiers of Macuxitermes are dimorphic, although the minor soldiers may be quite rare, while those of Noirotitermes and Acangaobitermes are monomorphic. Noirotitermes has prominent spine-like protuberances towards the posterior margin of the head capsule: the head capsules of Macuxitermes and Acangaobitermes lack such protuberances. Macuxitermes and Acangaobitermes soldiers possess a relatively long, slender nasus while that of Noirotitermes is short and broad. The pronotum of the former two genera is more-or-less saddle-shaped, yet has a clover-like appearance in Noirotitermes. Furthermore, the lateral margins of the thoracic nota of both major and minor Macuxitermes soldiers are adorned with short dark, stout spines which are absent in Noirotitermes and Acangaobitermes. Nevertheless, the group is distinguished by having soldiers with characteristic minute granulations on the surface of the head capsule, which are absent in all other Syntermitinae, and slender, sickle-shaped, piercing mandibles with a sharply pointed, marginal tooth.

There are also differences between the workers. The morphology of the mandibles—including the absence of ridges on the molar plates—and relative dimensions of the digestive tube are essentially the same among the three taxa; however, Macuxitermes workers are large and robust, while those of the other two genera are small, slender, and elongate. Only Macuxitermes workers have notal spines (similar to those of the soldiers). In all three genera, the digestive tube displays the complete dorsal torsion as defined by Noirot (2001), while the components are of very similar disposition and relative proportions. However, although the enteric valves share an almost identical shape, the arrangement and structure of the spines in Macuxitermes differs from that of Noirotitermes and Acangaobitermes.

Genera of Syntermitinae exhibit a wide variety of nest-building behaviour (Constantino 1991, Emerson 1952, Emerson and Banks 1965, Fontes 1985, Redford 1984, Scheffrahn 2010, Snyder 1922). Some build epigeal mounds (Cornitermes and Embiratermes spp.) or arboreal carton nests in rotten wood or tree stumps (Labiotermes spp., Silvestritermes holmgreni (Snyder)), while some, including species of Cyrilliotermes and Curvitermes, live in abandoned nests of other termite species or as inquilines. Labiotermes longilabius (Silvestri) builds “underground nests lined with blackish carton” (Silvestri 1903, cited in Emerson and Banks 1965) or “ladder” nests up the sides of trees. Other species construct diffuse underground nests and galleries e.g. Rhynchotermes bulbinasus Scheffrahn. The Macuxitermes group seems to fall into the latter category, although Rocha et al. (2012) suggest that these may also be mound inquilines of other species.

Specimens of Macuxitermes colombicus sp. n. were collected in Departamento Magdalena, Colombia, on 3 JUN 2009. Images of preserved specimens in 85% ethanol were made using an Olympus SZX9 stereomicroscope fitted with a LM Scope camera tube to an Olympus E-410 digital camera. Specimens were suspended in Purell® Instant Hand Sanitizer for transparent posturing support during photography. Enteric valve slide images were taken with an Olympus BH-2 compound microscope fitted with phase contrast optics. The entire worker P2 region was removed by micro-dissection and external muscle detached. Food particles were removed from enteric valve armature using an ultrasonic cleaner. The cleaned enteric valve was longitudinally cut, splayed open, and mounted on a microscope slide using PVA medium (BioQuip Products Inc.). External morphological terminology follows that of Roonwal (1969) and internal anatomical terminology that of Noirot (2001).

The new species was assigned to Macuxitermes after careful assessment and consideration of the morphological and anatomical data that have been assembled and reported on the component genera of Syntermitinae. Like M. triceratops, the head capsule of the soldier is endowed with fine microsculpture on the surface and the soldier and worker castes have notal spines, while the mandibles, mesenteric tongue and enteric valve of the workers match the descriptions of these structures in this species. However, several of these features are also found in members of the genus Armitermess. s.. Our species does in fact resemble Armitermes and differs conspicuously from M. triceratops in its appearance. The mandibles in the major soldier are less robust than those of M. triceratops and the postmentum, although very short, is not noticeably inflated. The profile of the nasus is straight rather than curved and the head capsule lacks the anterior processes of M. triceratops plus the occipital protuberances which are a feature of other members of the Macuxitermes group (Rocha et al. 2012). Furthermore, M. colombicus might not have minor soldiers.

Nevertheless, this termite does not fit readily into Armitermes either. The shape of the head capsule of the soldier differs from those of the three known species of Armitermes; nor is the minute pitting that covers its surface a characteristic of the latter. The labrum of M. colombicus soldiers is broadly rounded, while the mandibles have a distinctly different configuration from those of Armitermes spp.. As stated, Macuxitermes does share with Armitermess. s. the presence of notal spines in both soldiers and workers but this is not considered evidence of close relationship (Constantino 1997, Rocha et al. 2012). In addition, the notal spines on the new species are far more numerous and extensive than in Armitermes and the bristles of the pro-, meso- and metanotum of the soldier, reported by Rocha et al. (2012) as definitive of this genus, are lacking. In the worker, there is a greater degree of pilosity and the enteric valve is different from the type diagnostic of Armitermes spp.

Rather than create a new genus, the authors therefore place this species in Macuxitermes to which it seems to have the greatest affinity. As well as the previously listed similarities, it has the following in common with M. triceratops. Although worn down to some degree in all specimens examined, the second marginal tooth in the worker is reduced but distinct on both mandibles. Thus, all three marginal teeth are clearly visible on the left mandible. For consistency, the term “first-plus-second marginal tooth” should perhaps be retained for the left mandible, although the degree of fusion seems much less than in other genera and species of the sub-family.

The enteric valve of the worker very closely resembles that of M. triceratops. It is also very similar in appearance and constitution to those of Noirotitermes, Acangaobitermes, Embiratermes, Ibitermes, and Uncitermes (Constantino 1997, Cancello and Myles 2000, Rocha et al. 2012). However, it differs from these in having spines of equal length on the finger-like ridges, rather than spines that increase in length distally. The ridges in Ibitermes are also slightly dilated apically. Thus, the composition of the enteric valve may also be a diagnostic feature of Macuxitermes.

The absence of pulvillar spines as a generic feature is yet to be determined. Although pulvilli are described as “lacking armature or ornamentation” in Acangaobitermes (Rocha et al., 2011), the presence or absence of such is not reported for M. triceratops (Constantino 1997) or Noirotitermes (Cancello & Myles, 2000). Because of the apparent close similarity in appearance between the structure of the gizzard in M. colombicus and C. cumulans, it would be of interest if further studies could reveal the degree of uniformity of the gizzard’s musculature and cuticular armature throughout the sub-family, however.

It is possible that DNA analyses may provide greater insight into the relationship of M. colombicus with its congener. It is also possible that future field studies may yield further specimens of the species, including minor soldiers, thereby confirming its current taxonomic status. Until then, its placement in the genus Macuxitermes is in concordance with the available data.

Collected under permit no. 4120-E1-55958, Ministerio del Ambiente, Vivienda y Desarrollo Territorial, República de Colombia.