Abstract
The second- and third instar larvae of Platynectes (s. str.) decemnotatus (Aubé, 1838) are described and illustrated in detail for the first time, with special emphasis on morphometry and chaetotaxy. Larvae of P. decemnotatus can be distinguished from most other Agabinae by having secondary setae on the urogomphus and share with the other known species described in detail the presence of a ventroapical spinula on antennomere 3 and the absence of an occipital suture, natatory dorsal setae on tibia and tarsus and natatory setae on urogomphus. Platynectes decemnotatus larvae differ from larvae of Agabus Leach, 1817, Hydrotrupes Sharp, 1882 (currently in Hydrotrupini), Ilybiosoma Crotch, 1873, Ilybius Erichson, 1832 and the previously described Platynectes species in having a one-segmented urogomphus, a character previously observed only in larvae of Agabinus Crotch, 1873. The second- and third instar larvae of P. decemnotatus differ from those of P. (Agametrus) curtulus (Régimbart, 1899) in having the apical lateroventral process of antennomere 3 protruding (not protruding in P. curtulus). The third-instar larva of P. decemnotatus can also be distinguished from that of P. (Gueorguievtes) decempunctatus (Fabricius, 1775) by the absence of secondary dorsal setae on the tibia.
References
Alarie, Y. (1995) Primary setae and pores on the legs, the last abdominal segment, and the urogomphi of larvae of Nearctic Colymbetinae (Coleoptera: Adephaga: Dytiscidae) with an analysis of their phylogenetic relationships. The Canadian Entomologist, 127, 913–943.
https://doi.org/10.4039/Ent127913-6
Alarie, Y. (1998) Phylogenetic relationships of Nearctic Colymbetinae (Coleoptera: Adephaga: Dytiscidae) based on chaetotaxic and porotaxic analysis of head capsule and appendages of larvae. The Canadian Entomologist, 130, 803–824.
https://doi.org/10.4039/Ent130803-6
Alarie, Y. & Larson, D.J. (1998) Larvae of Agabinus Crotch: generic characteristics, description of A. glabrellus (Motschulsky), and comparisons with other genera of the subfamily Colymbetinae (Coleoptera: Adephaga: Dytiscidae). The Coleopterists Bulletin, 52, 339–350.
Alarie, Y., Spangler, P.J. & Perkins, P.D. (1998) Study of the larvae of Hydrotrupes palpalis Sharp (Coleoptera: Adephaga, Dytiscidae) with implications for the phylogeny of the Colymbetinae. The Coleopterists Bulletin, 52, 313–332.
Aubé, C. (1838) Hydrocanthares et gyriniens. In: Dejean, P.F.M.A. (Eds.), Species général des coléoptères de la collection de M. le Comte Dejean. Vol. 6. Méquignon Père et Fils, Paris, pp. i–xvi + 1–804.
https://doi.org/10.5962/bhl.title.8863
Bertrand, H. (1972) Larves et nymphes des coléoptères aquatiques du globe. F. Paillart, Abbeville, 804 pp.
https://doi.org/10.1002/iroh.19730580416
Gustafson, G.T., Short, A.E.Z. & Miller, K.B. (2016). New species of diving beetles in the subgenus Platynectes s. str. from the Guiana Shield (Coleoptera: Dytiscidae: Agabinae). Acta Entomologica Musei Nationalis Pragae, 56, 79–102.
Kawada, R. & Buffington, M.L. (2016) A scalable and modular dome illumination system for scientific microphotography on a budget. PLoS ONE, 11, e0153426.
https://doi.org/10.1371/journal.pone.0153426
Lawrence, J.F. (1991) Order Coleoptera. In: Stehr, F.W. (Ed.), Immature Insects. Vol. 2. Kendall/Hunt, Dubuque, IA, pp. 144–658.
Michat, M.C. & Archangelsky, M. (2009). Phylogenetic relationships of Leuronectes Sharp (Coleoptera: Dytiscidae: Agabinae) based on larval morphology and chaetotaxy. Insect Systematics and Evolution, 40, 209–228.
https://doi.org/10.1163/187631209X440078
Michat, M.C., Alarie, Y. & Miller, K.B. (2017) Higher-level phylogeny of diving beetles (Coleoptera: Dytiscidae) based on larval characters. Systematic Entomology, 42, 734–767.
https://doi.org/10.1111/syen.12243
Miller, K.B. & Bergsten, J. (2014) The phylogeny and classification of predaceous diving beetles (Coleoptera: Dytiscidae). In: Yee, D.A. (Ed.), Ecology, Systematics, and the Natural History of Predaceous Diving Beetles (Coleoptera: Dytiscidae). Springer, New York, pp. 49–172.
Nilsson, A.N. & Hájek, J. (2018) A World Catalogue of the Family Dytiscidae, or the Diving Beetles (Coleoptera, Adephaga). Version 1 January 2018. 306 pp. Available from: http://www.waterbeetles.eu/documents/W_CAT_Dytiscidae_2018.pdf (accessed 14 September 2018)
Ribera, I., Vogler, A.P. & Balke, M. (2008) Phylogeny and diversification of diving beetles (Coleoptera: Dytiscidae). Cladistics, 24, 563–590.
https://doi.org/10.1111/j.1096-0031.2007.00192.x
Toussaint, E.F.A., Hendrich, L., Hájek, J., Michat, M.C., Panjaitan, R., Short, A.E.Z. & Balke, M. (2017) Evolution of Pacific Rim diving beetles sheds light on Amphi-Pacific biogeography. Ecography, 40, 500–510.
https://doi.org/10.1111/ecog.02195
Watts, C.H.S. (1963) The larvae of Australian Dytiscidae. Transactions of the Royal Society of South Australia, 87, 23–40.
Wiley, E.O. (1981) Phylogenetics. The theory and practice of phylogenetic systematics. John Wiley & Sons, New York, 439 pp.