Pontomyia natans Edwards, 1926

Anderson, R. Charles, Adam, M. Shiham & Cheng, Lanna, 2023, Marine insects of the Maldives (Heteroptera: Gerridae, Hermatobatidae and Veliidae; Diptera: Chironomidae) with notes on taxonomy, Indo-Pacific distribution, and ecology, Raffles Bulletin of Zoology 71, pp. 478-490 : 488

Pontomyia natans Edwards, 1926

Pontomyia natans was first reported from the Maldives by Cheng (2004). In addition to the two samples reported by Cheng (2004; also listed in Table 1 as samples 1 and 3), two other samples are reported here (numbers 20 and 28); all were collected from shallow lagoons or small bays adjacent to islands. Pontomyia natans has the lowest habitat score (i.e., was the most inshore) of any of the marine insect species in our study ( Table 2). Although we have data from only four samples, their timings do suggest the possibility that P. natans shows both annual seasonality and lunar periodicity in its reproduction. Our marine insect samples were collected in every month of the year except July ( Table 1), and yet three of our four P. natans samples were collected between 21 March and 11 April, suggesting the possibility of reproductive seasonality; late March and early April is the calm inter-monsoon period when the northeast monsoon season gives way to the southwest monsoon. In addition, all four samples were collected close to the new or full moon, suggesting the possibility of adult emergence and reproductive activity in the Maldives being closely correlated with lunar cycles ( Table 3) and the tides, as has been reported for other Pontomyia species ( Cheng & Collins, 1980; Neumann, 1986; Soong et al., 1999). This is in contrast to the situation for P. natans in Taiwan, where it showed no clear pattern of emergence in relation to moon phase ( Soong et al., 1999). Note that due to a misprint in Cheng (2004: 56), species names were transposed, and in referring to the Taiwanese study the text should have read: “Adults of P. oceana emerged only during new moon or full moon periods while those of P. natans emerged almost every night during the study period”. Despite its tiny adult size and apparently limited ability to disperse, this species is widely distributed from the Maldives to Samoa; within Southeast Asia it has so far only been recorded from Pulau Tioman, Malaysia, as well as from Christmas Island ( Huang & Cheng, 2011; Huang et al., 2014). However, a phylogenetic study revealed that larval specimens of Pontomyia from Puerto Rico in the Atlantic were nested within the P. natans clade ( Huang et al., 2014); further study of this unexpected result is ongoing.