Pheidole parva
The following account is from Sarnat et al. (2015) and figure numbers refer to that publication.
Pheidole parva is a very small and inconspicuous species that is thus far reported only from Asia, a few localities in Arabia, and the islands of the Indian Ocean and the Pacific Ocean. It belongs to an Old World clade scattered across Indomalaya and into Oceania, and was treated as part of the P. rinae complex by Eguchi et al. (2007). The minor workers are completely covered in punctate sculpture and are difficult to differentiate from those of the Neotropical P. flavens complex. The similarity is so close that an introduced population of P. parva from the Seychelles was described by Forel, on the basis of the minor worker, as Pheidole flavens var. farquharensis.The similarity is entirely convergent, as these lineages are distantly related. Pheidole parva minors can be separated from those of the P. flavens complex most reliably by the interrupted striae that are interlaced among the punctate ground sculpture of the posterior head (Fig. 59vs. Fig. 60). This character can also be viewed in the dorsal view. Pheidole parva minors can be separated from those of the P. punctatissima clade treated here by the glossy gaster (Fig. 32vs. Fig. 33) and finer mesosomal hairs of unequal length (Fig. 54vs. Fig. 53). The major workers are characterized by a defined and moderately depressed antennal scrobe and a thick network of reticulated rugulae on the posterior lobes. This pattern is most similar to that of the broadly sympatric P. fervens and P. indica, but P. parva is much smaller than those species (HW < 0.95 mm vs HW > 1.10 mm) and lacks the distinct prominence on the posterior slope of the promesonotal dorsum (Fig. 4vs. Fig. 5). The majors of P. parva can be separated from those of the P. flavens and P. punctatissima group species treated here by the much stronger and more reticulated carinae which reach the posterior margin (Fig. 26vs. Fig. 25and Fig. 27) in addition to other characters given in the key. Readers are referred to Eguchi (2008; 2007)for characters separating P. parva from its Asian congeners.
Little is known about the biology of P. parva, but it does appear to be expanding its range and is worth monitoring in the future as it exhibits a high tolerance for disturbance. Eguchi (2008)observed that the species seems to inhabit open lands and forest edges, and has probably expanded its range in some part as the result of human commerce. Pheidole parva was one of the most commonly collected ants in a myrmecological study of agricultural fields in Vietnam and Okinawa (Anh et al. 2010; Suwabe et al. 2009). A recent study of 18 structure invading pest ants of healthcare facilities in Singapore found P. parva the most frequently encountered species (Man and Lee 2012). Pheidole parva and Pheidole megacephala were the two most common ant species encountered and together accounted for over 50% of the total collection (25.9% and 25.2%, respectively). In Mauritius and the Seychelles P. parva can be locally abundant and can be found in soil and leaf litter, under stones or root mats, in rotten logs, foraging on or nesting in the ground, as well as in lower vegetation and even under the bark of live trees (Fischer and Fisher 2013). It was collected there in parks, gardens, mangrove, coastal scrub, degraded dry forest, littoral and mixed forest, and rainforest, in elevations between 1–445 m. It was collected inland on the Arabian Peninsula from date tree orchards, banana plantations and under potted plants between 675–735 m elevation (Fischer and Fisher 2013).
Pheidole parva is not currently considered to be a significant pest species, and no impacts on agricultural systems or native ecosystems have been documented as of yet. The species is known to invade structures, however, and its prevalence in Singapore health care facilities (Man and Lee 2012)suggests it could become a more widespread nuisance pest in the future. Live colonies have been reported from various ships (Fischer and Fisher 2013)and should be screened for during quarantine inspections.
Diagnosis among introduced Pheidole. Yellowish brown to dark brown. Major | HW 0.85–0.92, HL 0.96–1.07, SL 0.41–0.45, CI 85–92, SI 45–51 (n=11, Eguchi et al. 2007). Head rectangular. Posterolateral lobes, including posterior head margin, covered in rugoreticulum. Antennal scrobes indistinct to moderately impressed, but frontal carinae always forming a border capable of accepting the antennal scape. Promesonotum in profile forming a single dome, lacking a distinct mound or prominence on the posterior slope. Promesonotum in dorsal view transverse with strongly projecting shoulders. Promesonotal dorsum rugoreticulate with distinct long longitudinal striae in addition to shorter sections of transverse and intersecting striae. Postpetiole not swollen relative to petiole. Minor | HW 0.39–0.50, HL 0.43–0.54, SL 0.38–0.46, CI 88–94, SI 84–102 (n=17, Eguchi et al. 2007). Posterior portion of head with many short to medium length segments of striae distinctly interlaced among punctate ground sculpture. Antennal scapes with erect to suberect hairs; scapes do not surpass posterior head margin. Promesonotum in profile forming a single dome, lacking a distinct mound or prominence on the posterior slope . Pronotal humeri angular. Hairs on mesosoma fine, flexuous, of unequal length and not arranged in pairs. Postpetiole not swollen relative to petiole; postpetiole narrow in dorsal view, only slightly broader than petiole.
Minors look like P. flavens complex species (P. flavens, P. navigans)
Distribution. Pheidole parva is considered here as native to the Indo-Malay region. The species is recorded from the Asian mainland from India east to China. We consider the records from Indonesia, Borneo, the Philippines and Taiwan to be native, but much of this distribution could represent a more recent anthropogenic expansion. We consider the records from the Okinawa and Kagoshima prefectures of Japan to be introduced along with the records from Palau to represent introduced populations, but it is difficult to know whether the species arrived in these islands before, with or after the arrival of humans. The species is introduced in the Seychelles, Mauritius, Saudi Arabia and the United Arab Emirates (Fischer and Fisher 2013). Pheidole parva was also collected from hothouses in Austria and Germany.
