Lachnodacnum luederwaldti, Orchymont, 1937

Clarkson, Bruno, Albertoni, Fabiano Fabian & FIKÁýEK, Martin, 2014, Taxonomy and biology of the bromeliad-inhabiting genus Lachnodacnum (Coleoptera: Hydrophilidae: Sphaeridiinae), Acta Entomologica Musei Nationalis Pragae 54 (1), pp. 157-194 : 182-185

Biology of Lachnodacnum luederwaldti

Almost all known specimens of this species were collected between the leaf bases of epiphytic and terrestrial bromeliads ( Fig. 18 ): we have recorded the species from the genera Aechmea Ruiz & Pav. , Billbergia Thunb. , Neoregelia L. B. Smith and Vriesea Lindl. A single adult was collected in the vegetation at the margin of a dam in Ecological Park Spitzkoft near Blumenau, Santa Catharina state in southern Brazil.

In the ¿eld, most egg cases were found attached to the basal portion of leaves within the bromeliad rosette (Fig. 19), usually on wet portions near the micro-pool or directly on the moist detritus. In captivity, adults laid eggs directly on the container wall near the water level or partially submerged. After hatching, the larva moves inside of the egg case, sometimes in a circular movement, before it cuts a hole in the silk layer of the egg case using its mandibles and leaving the egg case.

The larvae of all instars were observed submerged and sandwiched between the leaves. When they were not sandwiched, they were rapidly seeking for the place to be sandwiched. In the laboratory, when bromeliad leaves were not made available and the larva was not able to keep sandwiched after leaving the egg case, some larvae were observed to use the egg case as a shelter for a while. They opened the case in two places and stayed with the head in one aperture and with the spiracular atrium in the other. Eventually they went partly out of the shelter to hunt small crustacenas (copepods) that were near the shelter. It was not observed whether the larva that completely left the shelter returned. The larvae also fed on Enchytraeus sp. (Annelida: Enchytraeidae ) placed in the container, and were observed to feed on chironomid larvae in the ¿eld.

The pupae were found among the leaf bases, placed in a pupal chamber built by the third instar larva on the internal face of the more external leaves using the humid detritus available in the bromeliads rosette (Figs 20í22).

The adults are completely aquatic, living submerged in the ¿lm of water between the leaves of the bromeliads. In captivity, the adults also stayed submerged (Fig. 23). Usually they are not very active, but they forage among the leaves, probably feeding on the decaying material (detritus and decaying parts of bromeliad leaves) in the water. The unique specimen not directly collected inside a bromeliad was found at night on bush vegetation, which may indicate a nocturnal activity for dispersal.

Figures

Figs 18í23. Biology of Lachnodacnum luederwaldti Orchymont, 1937. 18 – micropool in the rosette of Neoregelia sp., a typical habitat; 19 – egg cases attached at the inner face of a bromeliad leaf; 20 – third instar larva and pupa in the detritus accumulated in the bromeliad rosette; 21í22 – pupa in the broken pupal chamber (21 – dorsal view; 22 – ventral view); 23 – adults staying submerged among bromeliad leaves in the rearing box. Figs 18í19, 23: photo B. Clarkson in Ubatuba Municipality, São Paulo; Figs 20í22: photo by F. F. Albertoni in Florianopolis, Santa Catarina.