Ilybius pleuriticus LeConte, 1850

Hicks, B. J. & Larson, D. J., 2000, Descriptions And Recognition Of Larvae Of Some Northern North American Species Of Ilybius Erichson (Coleoptera: Dytiscidae), The Coleopterists Bulletin 54 (1), pp. 36-59 : 41

Ilybius pleuriticus LeConte

Instar I. Colour. Dorsal surface of head, thorax and abdomen with a contrasting pattern of longitudinal dark brown and pale yellowish­brown stripes. Legs, urogomphi and ventral body surface pale yellowish brown. Head ( Fig. 1C ). HL 5 1.18 mm; HW 5 1.09 mm. Sides of head parallel. Legs ( Fig. 5 ). Femora with one proximal setae in PV series. Abdomen ( Fig. 2C ). Abdominal segments with numerous setae and spinulae. Terga 1–7 with dark spiniform setae; two dorsal, two ventral submedial and one lateral on each side. Sterna 1–3 with two small pale submedial setae; sterna 4–7 with two dark submedial spiniform setae, other small lighter coloured setae present but not prominent. LAS 0.44 times UT. Siphon relatively long, SI/LAS 5 0.38. Urogomphus with U4 spiniform, pale in colour and 0.27 times the length of U3; U2 and U3 longer, setiform and dark in colour.

Instar III. Colour ( Fig 6C ). Body darker than previous instars but still with evident contrasting pattern of pale and dark stripes. Head ( Fig 7C ). HL 5 2.44 mm, HW 5 2.29 mm. Sides of the head narrowing anteriorly. Legs ( Fig. 10 ). Femora secondary dorsal setae: profemur—five to seven; mesofemur five to seven, metafemur seven or eight; femora with spinulae in AV series. Abdomen ( Fig. 11C ). Dorsal surface with numerous short spiniform setae, primary setae setiform. LAS/UT 5 0.63

Ecology. Both adults and larvae of I. pleuriticus were collected from large bog pools and along the edges of ponds. They were common among emergent vegetation but were also collected further out from the edge. In one instance, a gravid female was collected in a temporary pool and this adult laid several eggs that hatched in mid­September. The collection of instar I larvae and the hatching dates support the general univoltine life history pattern described by Hicks and Larson (1995) for Ilybius from Newfoundland.

Figures

Fig. 1. Dorsal surface of the head of instar I larvae of three species of Ilybius Erichson. A I. biguttulus, B I. discedens, C I. pleuriticus.

Fig. 5. Ilybius pleuriticus. Instar I, right legs, anterior and posterior aspects.

Fig. 2. Last three abdominal segments and urogomphi, dorsal aspect, of instar I larvae of three species of Ilybius Erichson. A I. biguttulus, B I. discedens, C I. pleuriticus.

Fig. 6. Dorsal body surface of instar III larvae of three species of Ilybius Erichson. A I. biguttulus, B I. discedens, C I. pleuriticus.

Fig. 7. Dorsal body surface of head of instar III larvae of three species of Ilybius Erichson. A I. biguttulus, B I. discedens, C I. pleuriticus.

Fig. 10. Ilybius pleuriticus. Instar III, right legs, anterior and posterior aspects.

Fig. 11. Last two abdominal segments and urogomphi, dorsal aspect, of instar III larvae of three species of Ilybius Erichson. A I. biguttulus, B I. discedens, C I. pleuriticus.