A Description of the Mature Larva of Neoporus dimidiatus (Gemminger and Harold, 1868) (Coleoptera: Dytiscidae: Hydroporinae) with Notes on its Natural History

Mature larvae of Neoporus Guignot, 1931 collected from an Oklahoma stock pond and outlet stream were cultured into the adult stage, and identified as N. solitarius (Gemminger and Harold, 1868). Chaetotaxy of legs and urogomphi is comparable to that of previously described Neoporus, including secondary sensilla on the proximal urogomphal segment. Mandibular geometric parameters were as follows: MMD/ML, 0.10 ± 0.02; MBD/ML, 0.27 ± 0.03; angle of attack (AA), 46.6 ± 1.9°; lateral arc (Larc), 119.6 ± 2.9°; medial arc (Marc), 78.2 ± 5.2°. Respective cranial temporal curvature and orientation were 73.2 ± 8.6° and 13.9 ± 1.3°. Significant differences between dorsal and ventral intermandibular distances (DID = 0.71 ± 0.04 mm vs. VID = 0.49 ± 0.03 mm) appear to be major architectural and geometric features facilitating the oblique opening and closure of mandibles during prey capture and feeding

A Redescription of the Mature Larva of Thermonectus basillaris (Harris) (Coleoptera: Dytiscidae: Dytiscinae)

Mature larvae collected from Georgia ephemeral habitats were cul­tured into the adult stage and identified and described as Thermonectus basillaris.The legs of T. basillaris have fewer spiniform sensilla than reported for Acilius mediatus, and it appears that its two large dorsal stemmata are more massive than those of A. mediatus. These morphological differences indicate that nek­tonic larvae of T. basillaris and A. mediatus may be exploiting dif­ferent prey regimes

Mature Larvae of Hydroporus signatus Sharp (Coleoptera: Dytiscidae) as Substrates for Peritrichida

Mature larvae of Hydroporus signatus Sharp collected from a small eutrophic habitat served as substrates for Peritrichida (Ciliophora). The rate of infestation was 60% and there were indications of body site specificity for the colonies with most found attached to the cra­nium and/or mouthparts

Corrections for Identification of Mature Larvae of Rhantus calidus (Fabricius) and Hoperius planatus Fall (Coleoptera: Dytiscidae) in Georgia

Characters for identification of mature larvae of Rhantus calidus and Hoperius planatus in Georgia are evaluated and critiqued. Ma­ture larvae of R. calidus have only eight cereal sensilla (setae) while those of Hoperius have numerous medial and lateral sensilla. This is presented as an obvious and reliable character set for identification of R. calidus and H. planatus in Georgia

An Allometric Analysis of Ontogenetic Changes (Variation) in the Cranial Morphology of Larvae of Hydaticus bimarginatus (Say) (Coleoptera: Dytiscidae: Dytiscinae)

Distortion coordinates (Cartesian transformations) are used to compare the ontogenetic allometry in cranial morphology of first, second, and third instars of Hydaticus bimarginatus (Say). The most significant difference in the dorsoventral view is the expansion of the posterior lateral margins. Cranial expansion is likely due to an increase in the mass of the adductor muscles which are responsible for closing the mandibles. The ontogenetic shift in head orientation to a more subprognathic position evident in the analysis of lateral silhouettes indicates that second and third instars may be adapted to feeding on substrate associated prey. These differences are thought to reflect possible changes in prey regimes and habitat preference occurring during larval development

A Redescription of the First Instar of Rhantus calidus (Fabricius) (Coleoptera: Dytiscidae) with Notes on its Biology

First instars of Rhantus calidus (Fabricius) representing a Georgia population are described and illustrated. Dimensions are provided along with an analysis of the primary chaetotaxy of legs, head, and last abdominal segment. The presence of first instars at the study site demonstrated that R. calidus either requires or is at least tolerant of warmer temperatures for completion of its life cycle. Habitats with temperatures comparable to this site were likely present in a warm Atlantic coastal enclave during the last glacial maximum (LGM), making it probable that the LGM dytiscid fauna of Georgia included R. calidus

A Description of the Third Instar of Platambus flavovittaus (Larson and Wolfe, 1998) with Comments on the Larval Morphology of Platambus stagninus (Say, 1823) and a Key to the Agabini (Coleoptera: Dytiscidae) of Georgia

Mature Agabini larvae collected from a small temporary road-side habitat were reared to the adult stage and identified as Platambus flavovittattus (Larson and Wolfe, 1998). The mature larva is described and illustrated with an emphasis on leg morphology. Important differences between cranial temporal curvatures of P. flavovittatus and P. stagninus (Say, 1823) are described. A larval key is constructed to facilitate identification of Georgia agabine genera and species

Variation in Stemmatal Morphology of Larvae of Liodessus noviaffinis Miller (Dytiscidae: Hydroporinae: Bidessini)

Second and third instars tentatively identified as Liodessus noviaffinis Miller have six dorsolateral stemmata near the origin of each antenna. However, each stemma lacks a corneal (cuticular) lens on the surface exterior to its internal sensory pigmented components

TW Hydrae: evidence of stellar spots instead of a Hot Jupiter

TW Hydrae shows significant radial-velocity variations in the optical regime. They have been attributed to a 10 Jupiter Mass planet orbiting the star at 0.04 AU. In this work, we have tested whether the observed RV variations can be caused by stellar spots. We have also analyzed new optical and infrared data to confirm the signal of the planet companion. We fitted the RV variations of TW Hya using a cool spot model. Our model shows that a cold spot covering 7% of the stellar surface and located at a latitude of 54 deg can reproduce the reported RV variations. The model also predicts a bisector semi-amplitude variation <10 m/s, which is less than the errors of the RV measurements discussed in an earlier publication. The analysis of new optical RV data, with typical errors of 10 m/s, shows a larger RV amplitude that varies depending on the correlation mask used. A slight correlation between the RV variation and the bisector is also observed, although not at a very significant level. The infrared H-band RV curve is almost flat, showing a small variation (<35 m/s) that is not consistent with the optical orbit. All these results support the spot scenario rather than the presence of a hot Jupiter around TW Hya.Comment: accepted for publication in A&