Department of Zoology

Studies on the fruit feeding weevil, Paramecops farinosa (Coleoptera Curculionidae) in Sri Lanka as a prospective weed biological control agent of the invasive weed, Calotropis spp.

2020-12-29T00:00:00Z

Studies on the fruit feeding weevil, Paramecops farinosa (Coleoptera Curculionidae) in Sri Lanka as a prospective weed biological control agent of the invasive weed, Calotropis spp. Wijeweera, W.P.S.N.; Senaratne, K.A.D.W.; Dhileepan, K. Calotropis gigantea is a large shrub or a small tree native to Sri Lanka with an Ayurvedic medicinal value. The plant is considered as an invasive weed in countries where it has been introduced. Paramecops farinosa Schoenherr (Aak weevil) is a monophagous pest that feeds on C. gigantea. Present study was conducted to elucidate the life history and damage potential of P. farinosa, in order to assess its potential as a biological control agent against C. procera and C. gigantea in countries where the plants are invasive. The field sampling was done throughout Sri Lanka covering 120 sampling sites from December 2014 to October 2015, and C. gigantea fruits were examined for the incidence and intensity of damage by P. farinosa. It lays yellowish, oval and mostly one-clustered eggs in the inner-pericarp fibrous layer of the Calotropis fruit. Newly emerged larvae were apodous, pale yellowish-white with brown head capsule whereas developing larvae were creamy-white, curved and stout. Paramecops farinosa larvae voraciously feed on all Calotropis seeds (100%) and fifth larval instar pupated by forming silky cocoons within the seed chamber. The adults feed on leaves, buds and flowers and its damage is highly correlated with the amount of P. farinosa inhabit on trees. P. farinosa is a seed predator and highly damage reproductive structures of C. gigantea thus directly influences the reproductive ability of the plant. These results provide baseline information needed in adopting P. farinosa as potential biological control agent against C. procera and C. gigantea.

Distribution, development biology and behavior of Dacus persicus associated with Calotropis gigantea in Sri Lanka

2021-07-27T00:00:00Z

Distribution, development biology and behavior of Dacus persicus associated with Calotropis gigantea in Sri Lanka Wijeweera, W.P.S.N.; Senaratne, K.A.D.W.; Dhileepan, K. Calotropis gigantea (Crown flower, Giant milkweed or Wara) is a native medicinal plant in Sri Lanka. It is recorded as an invasive plant in Australia, Brazil, USA, etc. Dacus persicus is recorded as a highly destructive monophagous pest of C. gigantea in Sri Lanka. Larvae of D. persicus feed on developing fruits and seeds and reduce the reproductive output of the plant significantly making it a suitable candidate for biocontrol. Therefore, the present study was aimed to investigate the distribution and reproductive biology of Dacus persicus to assess the potential as a biocontrol agent for Calotropis species. D. persicus distributed in six provinces in Sri Lanka. The duration of mating and ovipositing of D. persicus was 54 and 92 minutes, respectively. It laid eggs in the seed chamber of developing fruits and the fruit size is highly correlated (p < 0.001, r = 0.990) with the number of laid eggs. Only one egg cluster of D. persicus found within a single fruit having 18.5 (± 0.85) eggs per cluster and the eggs hatched in 3 days. The duration of larval and pupal stages for D. persicus were 24 and 12 days, respectively. These results provide essential information needed in adopting D. persicus as a biocontrol agent of C. gigantea.

Determination of the distribution of Calotropis gigantea (L.) in Sri Lanka using MaxEnt modelling technique

2021-12-21T00:00:00Z

Determination of the distribution of Calotropis gigantea (L.) in Sri Lanka using MaxEnt modelling technique Wijeweera, W.P.S.N.; Senaratne, K.A.D.W.; Dhileepan, K.; De Silva, M.P.K.S.K. Calotropis gigantea is a drought-resistant, salt-tolerant, native plant in Sri Lanka with ayurvedic medicinal values. The plant is used for fiber, fodder and fuel, as well as a fertilizer. Despite its benefits, C. gigantea has become an emerging problem in countries where it has been introduced because of its invasiveness. Although C. gigantea is widely distributed in Sri Lanka, precise information on its distribution is lacking. Therefore, the present study was aimed at determining the distribution of C. gigantea in Sri Lanka. Field surveys were conducted in 120 sites covering all provinces in Sri Lanka from December 2014 to June 2015 to record the occurrence of C. gigantea. C. gigantea was distributed in all provinces except the Central province. It was more widespread along coastal regions, but its occurrence was low in the Western and Sabaragamuwa provinces. MaxEnt modelling predicted that the entire coast of Northern, North-Central and Eastern provinces contain the highest probability of C. gigantea distribution whereas the low probability was in North-Western, Western, Southern, Uva, Central, and Sabaragamuwa provinces. No occurrence probability was predicted in certain regions of Southern, Sabaragamuwa, Uva, and Central provinces of Sri Lanka. The study provides information on the current and potential distribution range of C. gigantea in Sri Lanka.

An update on the status and distribution of the Knob-billed Duck Sarkidiornis melanotos in Sri Lanka with notes on its behaviour.

2022-04-06T00:00:00Z

An update on the status and distribution of the Knob-billed Duck Sarkidiornis melanotos in Sri Lanka with notes on its behaviour. Saranga, B.G.P.T.; Wijeweera, W.P.S.N.; Kannan, R. he Knob-billed Duck or African Comb Duck Sarkidiornis melanotos was formally described to science from Ceylon (now Sri Lanka) by Pennant (1769: 12). It disappeared and was believed to be extinct from the island by the 1960s (Henry 1998; Harrison & Worfolk 1999). Ali & Ripley (1987: 48) indicated the species as ‘Formerly sparse resident in Ceylon.’ Carboneras & Kirwan’s (2020) global distribution map for the species does not include Sri Lanka. The historical status of the duck in Sri Lanka is dubious and must be interpreted through numerous subjective statements. Legge (1880: 1064) wrote that the bird was ‘more common than is generally supposed…’ and that it was first described in Ceylon by Forster, ‘who erroneously states that it is common in the hills’ (ibid.). Legge himself characterized the status of the Comb Duck in the island as ‘… nowhere numerous, it is found here and there in … the north and east …’ (ibid.). Citing Layard, he wrote that it is ‘… not uncommon on the tanks of the Vanni …’ (ibid.). Also citing one ‘Mr. Parker’ [= H. Parker], (apparently based on Parker 1881, 1883) he wrote that the bird is ‘tolerably common, but not plentiful, in the North-western Province and in the Anaradhapura (sic) district …’ (ibid.). As for breeding, Legge wrote that one Mr. Fisher found it breeding near Yala (ibid.). The breeding season has been reported as February– March in Sri Lanka (Legge 1880; Henry 1971; Weerathunga et al. 2013). Based on these reports, we surmise that, prior to its disappearance, the species was never common but occasionally nested in the island. Young (2005: 392) indicated in the map that the species occurs in Sri Lanka, although the text (p. 393) says the contrary.