Myrmicaria aphidicola

This is one of only two species of Myrmicaria (the other is Myrmicaria brunnea) known to be associated with aphids.

Identification
Zettel et al. (2018) - In exact full-face view, eyes breaking outline of head. Scape relatively long, SI = 104-117. Anteroventral pronotal spines prominent. Sides of mesonotum weakly bulging; posterior surface with longitudinal rugae (except in small specimens). Medial carina of mesonotum not extended onto propodeum. Node of petiole moderately widened in dorsal aspect. Propodeal spines long, directed dorsocaudally, not continuing dorsal outline of propodeum. Peduncle of petiole long. Base of gaster tergite 1 with distinct striation. Specimens quite variable in size and sculptural details.

Hitherto, M. aphidicola is the only described Philippine species with distinct basal striation on gaster tergite 1. However, there are about three similar undescribed species ranging from southern Luzon to Leyte with the same character. Further diagnostic characters are the rather prominent anteroventral pronotal spines, a deep metanotal groove, length and direction of propodeal spines, and a long peduncle of the petiole.

All studied specimens from the Mt. Apo area are pale yellow, probably due to long storage in alcohol. Therefore, brown specimens from Bukidnon were used for the description of colour, which matches with the original description (compare Calilung, 2000). The Bukidnon specimens also differ from the other examined specimens by slightly larger size and longitudinal rather than reticulated rugae on the head.

Calilung (2000) - This species differs from Myrmicaria brunnea in having all the gastral segments uniformly brown while brunnea has the basal margin of the five terminal, segments dark brown. They differ also in size wherein according to Saunders' original description (1841), this ant is 6/10 to 8/10 inch, which is much bigger than aphidicola. Saunders' descriptions were all based on coloration and very short descriptions.

Distribution
Myrmicaria aphidicola is recorded from a few localities in the central part of Mindanao. Recorded altitudes range between 630 (Kaamulan) and 1,300 m a.s.l. (Lake Agco).

Distribution based on Regional Taxon Lists
Indo-Australian Region: Philippines.

Biology
Calilung (2000) - Bolton (1973) reported that the Myrmicaria are general predators and scavengers, but this species is found associated with aphids. However, they are not totally dependent on the honeydew secreted by the aphid since small pieces of grasshoppers and beetles were also found inside the nest.

These ants build their nest on the leaf sheath of Phragmites sp. (Poaceae) and inside the nest are aphids,. They protect these aphids by building a nest over them and the ants benefit from the honeydew provided by the aphids. These ants do not totally depend on the honeydew secreted by these aphids because nests were seen with dead insects like small grasshoppers and beetles. According to Bolton (1973), these ants made nests directly into the earth, often with long sunken runways visible on the surface of the ground.

I observed that their nests are not only made of soil but also mixed with pieces of dried plant parts like stems and leaves. There are some traces of soil particles going up to the leaf sheath where the nest is built.

Nomenclature

 *  aphidicola. Myrmicaria aphidicola Calilung, 2000: 68, fig. 2 (w.) PHILIPPINES (Mindanao).

Worker
Body 5-6 mm long, reddish brown to brown, with numerous long and coarse setae.

Head longer than broad, subquadrangular and roughly seulptured; mandibles large, short and triangular, with linear sculpturing; apical margin behind first tooth with four exposed unequal and loosely spaced denticles; antennae 7 -segmented, club indistinct, antennal sockets close to basal margin of clypeus, antennal scrobes absent; frontal carinae widely separated; clypeus convex, triangular at basal margin, lined with long setae; eyes large, as long as first funicular segment, elevated.

Pronotum and mesonotum separated by very weak promesonotal suture, suboctagonal, elevated but flat dorsally, sharply angled laterally and roughly sculptured; mesonotum bluntly bituberculate, posterior portion more or less vertical; metanotal groove deeply impressed; propodeum lower than pronotum and mesonotum, with a pair of spines or bispinose positioned posteriorly, sharply angled laterally; legs long and slender with numerous long, erect setae; forelegs with large tibial spur fringed with hairs on inner margin; fore tarsal segments with fringed hairs ventrally or on inner margin.

Petiole and post petiole rounded and elevated with numerous erect and long setae; petiole with long anterior peduncle; gaster elongate-oval with numerous long and short setae; gastral segments one and two large and subequal, almost covering the whole gaster; only three gastral segments visible when viewed dorsally; third gastral segment four times smaller than segment one or segment two; sting visible, long and somewhat flattened from side to side.

Zettel et al. (2018) - (n = 32): HW 1.24–1.76; HL 1.22–1.67; SL 1.41–1.83; SW 0.13–0.18; TL 5.22–7.21; Pmin 0.11–0.22; PW 0.29–0.49; PPW 0.34–0.52; SpD 0.22–0.42; PrL 0.67–0.99; FeL 1.83–2.45; ML 1.57–2.22; PnW 0.72–1.21; CI 98–109; SI 104–117; FeI 136–154.

Structures: Head roundish to slightly transverse; dorsally usually with distinct reticulate rugae, but in some specimens with more prominent longitudinal rugae; laterally always with fine longitudinal rugae. Clypeus with median carina not reaching foremargin; sides with very variable longitudinal rugae, almost absent in small specimens. Mandible with sharp longitudinal rugae; apical margin with four teeth. Mesosoma with median carina on pronotum and mesonotum, posteriorly often not reaching hind margin. Pronotal dorsum usually with coarse reticulated rugae, but in few specimens with more pronounced longitudinal rugae; anteroventral teeth prominent. Mesonotum in addition to the median carina with scarce sculpture and a sharply elevated transverse carina; sides strongly, angularly elevated. Metanotal groove narrow and deep; in dorsolateral view lateral margin forming an acute angle. Sides of mesosoma with longitudinal rugae, usually reduced on sides of propodeum. Dorsum of propodeum with reduced sculpture, often with fractions of a transverse carina or of longitudinal carinae; area between bases of spines strongly concave in dorsal aspect. Propodeal spines long, directed upward in relation to anterior outline of propodeum, slightly to moderately diverging in dorsal aspect. Nodes of petiole and postpetiole rounded; peduncle of petiole long. Gaster with piliferous punctures and with fine but distinct striation at base of gaster tergite 1.

Setae abundant on trunk and appendages. Dorsal setiferation composed of two types of setae, short setae about half as long as long ones. On head dorsum, petiole and postpetiole all setae suberect. Short setae abundant on mesosoma sides, but sparse on its dorsum. On gaster, long setae suberect, short setae subdecumbent anteriorly, suberect posteriorly.

Colour (Bukidnon specimens): Trunk light to medium brown; head dorsally infuscated in few specimens, gaster variably infuscated. Antennae and legs light brown. Setae whitish.

Type Material
HOLOTYPE: Worker, Mindanao: North Cotabato: Kidapawan:Agco, Mt. Apo, on leafsheath of Phragmites sp., 00.v 1988 (MY.J. Calilung, MVJC 026) (UPLB-MNH). PARATYPES: 8 workers, same data as holotype (UPLB-MNH).

Etymology
From the observed association with aphids.

References based on Global Ant Biodiversity Informatics

 * Calilung, M.V.J. 2000. A new genus, two new species and a new subspecies of Philippine ants. Philipp. Entomol. 14: 65-73