Patricia L. M. Torres

Larval morphology of Macrovatellus haagi (Wehncke) and phylogeny of Hydroporinae (Coleoptera: Dytiscidae)

The three larval instars of Macrovatellus haagi (Wehncke) are described and figured for the first time. Detailed morphometric, chaetotaxic and porotaxic analyses are provided. They are compared with the immatures of other species of the genus and the tribe Vatellini. Tribal- and generic-level larval characters are identified based on the descriptions herein provided and those found in the literature. A Vatellini larva is distinguished by its very characteristic nasale, antennomere 1 and maxillary stipes elongate, prementum as long as broad, and very long siphon and urogomphi. Macrovatellus Sharp differs from Derovatellus Sharp by the presence of lateral spinulae on prementum, and secondary setation on antennomeres 1 and 2 and maxillary palpomere 1. Third instar of M. haagi differs from M. mexicanus Sharp by its one-segmented labial palpi and siphon shorter than cerci. A phylogenetic analysis based on 57 larval characters and including members of six tribes of the Hydroporinae was conducted. It supports the hypothesis of a derived condition of the tribe Vatellini within this subfamily. The clade Bidessini + Vatellini + Hyphydrini and the clade Vatellini + Hyphydrini are well supported. Several characters suggest a monophyletic origin of the tribe Vatellini, and two synapomorphies support monophyly of the genus Macrovatellus.

Hydaticus tuyuensis Trémouilles (Coleoptera: Dytiscidae): Larval Morphology and Phylogenetic Relationships within Dytiscinae

The three larval instars of Hydaticus (Guignotites) tuyuensis Trémouilles are described and illustrated for the first time, emphasizing the morphometry and chaetotaxy. Second- and third-instar larvae of the known species of the subgenus Guignotites Brinck are characterized by a trilobate median process of prementum. All larval instars of H. tuyuensis, however, have a bilobate process, similar to that present in the known species of the subgenus Hydaticus Leach. This implies that a trilobate process cannot be used as a diagnostic character for Guignotites. Alternatively, Guignotites as presently defined may not represent a natural group. A cladistic analysis of 57 larval characters suggests that the genus Hydaticus shares a common origin with the clade composed of the genera Eretes Laporte and Thermonectus Dejean, based on the following synapomorphies: (i) abdominal segment VII almost completely sclerotized ventrally; the absence of (ii) additional ventroapical pores on the third antennomere, (iii) setae FE4 and FE6, (iv) additional setae on the femur and (v) additional setae on the tibia; and the presence of (vi) setae on the median process of prementum and (vii) spinulae on the second labial palpomere. A bilobate or trilobate median process of the prementum and the submedial insertion of seta AN3 distinguish Hydaticus from the remaining genera of Dytiscinae studied.

The Unknown Larva of Anodocheilus Babington (Coleoptera: Dytiscidae: Hydroporinae: Bidessini): Description of A. maculatus Babington and Chaetotaxic Considerations

Abstract Larval morphology of the New World dytiscid genus Anodocheilus Babington is studied. For this purpose, the three larval instars of A. maculatus Babington are described and illustrated for the first time, with particular emphasis on the morphometry and chaetotaxy. First-instar larva of Anodocheilus can be distinguished from those of Liodessus Guignot and Amarodytes Régimbart (the only other bidessines known as first instars) in its more elongate siphon. All Bidessini genera known as first-instar larvae are characterized by the absence of pore ABc. This pore is consistently present in the remaining hydroporines. Third-instar larva of Anodocheilus has an elongate siphon and a short first urogomphomere. These features link the genus to Uvarus Guignot and Bidessus Sharp. The remaining known Bidessini genera have a short siphon and an elongate first urogomphomere. The presence of two contiguous pores on a very small bulge in the stipes of Anodocheilus larvae reinforces the hypothesis that hydroporines lost the galea secondarily.

A preliminary study on the phylogenetic relationships of Copelatus Erichson (Coleoptera: Dytiscidae: Copelatinae) based on larval chaetotaxy and morphology

The phylogenetic relationships of the diving-beetle (Dytiscidae) subfamily Copelatinae are not well known. Some authors postulated a sister-group relationship between Copelatus Erichson and the remaining Dytiscidae, relying mainly on the absence of a mandibular channel in Copelatus. Other authors suggested a more derived position of the genus. Larval characters have been underutilized in phylogenetic studies, mainly because the larvae of many taxa within the family and, in particular, within Copelatinae are unknown. A comprehensive approach aimed to study the phylogenetic placement of a member of this subfamily based on larval characters has not been produced so far. In this study, the phylogenetic relationships of Copelatus are explored based on a cladistic analysis of 24 taxa and 120 chaetotaxic and morphological characters from larvae. For this purpose, larvae of Copelatus longicornis Sharp are described and illustrated in detail for the first time, with particular emphasis on morphometry and chaetotaxy, with the latter being unexplored until now. The results support a derived position of Copelatus within Dytiscidae, with a sister-group relationship between this genus and a clade formed by the subfamilies Lancetinae, Coptotominae, Laccophilinae, Colymbetinae, Matinae, and Dytiscinae, and part of Agabinae. No evidence was found for a sister-group relationship between Copelatus and the remaining Dytiscidae so that the absence of a mandibular channel in this genus is likely a reduction. Copelatus is supported by three apomorphies within Dytiscidae: mandibular channel absent, internal margin of the stipes with three robust spinulae, and seta MX8 inserted subapically on the galea.

Descriptions of the preimaginal stages of Lancetes marginatus (Steinheil) and L. biremis Říha (Coleoptera: Dytiscidae), and comparative notes with other Lancetes larvae

Abstract All the preimaginal stages of Lancetes marginatus (Steinheil) and third instar larva of L. biremis Říha are described and figured for the first time. Detailed analyses of the morphometry, chaetotaxy and porotaxy are provided, and comparisons with the immatures of other species of the genus are included. The larvae described have multifragmented urogomphi, the only larval synapomorphy that defines the genus Lancetes Sharp. Third instars also present a secondary subdivision in some of the cephalic appendages, which is a synapomorphy of Lancetes plus Dytiscinae. First instar larva of L. marginatus is distinguished from the remaining known first instars of Lancetes by the absence of primary pores FRe and MXa, and the presence of one additional minute seta on the dorsal surface of antennomere 4 and one additional pore on the urogomphus. The third instar of L. marginatus is unique by the absence of secondary dorsal setae on the femur. The pupa of L. marginatus differs from that of L. angusticollis by the presence of fewer setae on the head, pronotum and abdominal terga V to VIII.

Larval morphology of Thermonectus succinctus (Aubé 1838) (Coleoptera: Dytiscidae: Dytiscinae), with biological notes and chaetotaxic analysis

Abstract The three larval instars of Thermonectus succinctus (Aubé 1838) are described and illustrated for the first time, emphasizing the morphometry and chaetotaxy. Biological notes are included. Thermonectus Dejean is distinguished from other Aciliini genera by its slightly bifid median process of the prementum, which bears two spine-like setae (LA8). First instars of T. succinctus differ from those of Acilius Leach and Graphoderus Dejean in the lower number of additional anterodistal setae on the femur. The shape of seta TA1 and the presence of an additional posterior pore on the tibia separate first instars of Graphoderus from those of Acilius and T. succinctus. Regarding the mature larva, T. succinctus differs from T. alfredi Griffini 1898 in its smaller size, from T. basillaris (Harris 1829) in the lack of a row of minute hairs along the internal margin of the galea, and from T. nigrofasciatus ornaticollis (Aubé 1838) in the shorter length of seta LA8.

Immature Stages of Hydrobiomorpha spinosa (Orchymont, 1928) (Coleoptera: Hydrophilidae)

The preimaginal stages of the Neotropical species Hydrobiomorpha spinosa (Orchymont) are described and figured for the first time. They are compared to the larvae of the New World species Hydrobiomorpha casta (Say) and to unidentified African and Australian larvae. Bionomical notes on this species are included.

Description of immatures of Berosus decolor Knisch, 1924 (Coleoptera: Hydrophilidae: Berosini), with emphasis on chaetotaxy and morphometry

The preimaginal stages of Berosus decolor Knisch, 1924 are described for the first time, including illustrations of the egg case and all larval instars. Larval morphology of this species is studied emphasizing chaetotaxic and morphometric analyses. The egg case lacks a mast and contains 2‒3 eggs; all larval instars are characterized by the following features: presence of 6 teeth on anterior margin of nasale; left epistomal lobe carrying 14‒16 strong and curved setae (gFR2); seta FR1 elongate, inserted posteriorly to seta PA7; pore FR14 absent; parietale with spinulae in the area between setae PA5 and PA12; mandibles asymmetrical; seta MN1 minute; first antenommere with a digitiform projection on distal inner margin; antennal sensilla AN8 and AN9 absent; maxillary sensilla MX10 hair-like, MX11 and MX16 with an intermediate shape between hair-like and spine-like; labial sensilla LA4 and LA15 absent; seta LA2 present, minute; abdomen with 7 pairs of tracheal gills. The morphology of the egg cases and larvae within the genus Berosus are compared and discussed.

Description of immatures of the genus Tropisternus Solier, subgenus Pristoternus Orchymont (Coleoptera: Hydrophilidae), with emphasis on the chaetotaxy and morphometry of larval forms

The egg cases, larvae, and pupae of Tropisternus (Pristoternus) latus (Brullé, 1837), T. (P.) ovalis Castelnau, 1840, and T. (P.) laevis (Sturm, 1826) are illustrated and described for the first time. The egg cases are built with or without a mast, which can be ribbon-like or globular; all larval instars have seven anterior denticles in the anterior margin of nasale, and the antennal seta AN8 is present; the pupae bear 6 or 8 styli on the abdominal segments II-VI, the pleural styli can be either short or very long, and horn-like projections may be present on the abdominal segments II-VI. A comparison of the morphology of the egg cases, pupae and larval chaetotaxic and morphometric characters within the genus Tropisternus is presented.

The Unknown Larva of the Minute Diving Beetle Genus Brachyvatus Zimmermann, 1919 (Coleoptera: Dytiscidae: Bidessini)

ABSTRACT: The three larval instars of Brachyvatus acuminatus (Steinheil, 1869) (the type species of the bidessine genus Brachyvatus Zimmermann, 1919) are described and illustrated for the first time including detailed morphometric and chaetotaxic analyses of the cephalic capsule, head appendages, legs, last abdominal segment and urogomphi. Larvae of this genus are characterized by the absence of the primary pore ABc, which is a synapomorphy of the tribe Bidessini. Brachyvatus larvae can be separated from those of all other known Bidessini genera by the following combination of characters: very small size; lateral branches of nasale well visible in dorsal view; ventroapical spinula on third antennomere absent; meso- and metatergite of instar I with anterotransverse carina; siphon short; long urogomphi with secondary setae; seta PA3 absent; setae UR2 and UR4 inserted contiguously; natatory setae present on tibiae in instars II–III.