Previous studies which investigated macroinvertebrate colonization of submerged wooden substrates in streams and lakes did not consider the wood species. In this study, the genus of randomly collected twigs and branches from two streams was determined microscopically using morphological and structural characteristics of the wood genera. The macroinvertebrate colonization of the wooden substrates was analysed with respect to the different kinds of the twigs and branches. Additionally, an exposition experiment was conducted with the most commonly found wood genera, alder (Alnus) and oak (Quercus), in two different states of decay (freshwood and conditioned wood). The colonization experiment stressed the results of the natural wood samplings that the wood genus plays only a minor role in the colonization by macroinvertebrates.

Abstract. The larvae of Lypephaeopa (Stephens, 1836) are found on dead wood substrates in streams and lakes. Gut content analy ses, scanning electron microscopy of larval mouthparts, and gallery structure revealed characteristics of this habitat preference. The guts of the larvae contained mainly wood fragments whereas other food items (detritus, algae, fungi, inorganic particles) were much rarer. The suitability of the mouthparts to scrape wood surfaces, and the adaptative elongation of the silk-secreting spinneret, which facilitates the construction of retreats consisting of a tunnel-like silken net incorporating mainly wood fragments, are discussed. Retreat-construction under laboratory conditions indicated that larvae exploit new feeding areas by steadily extending their galleries.Tips of the maxillary palps bear five sensilla styloconica and five sensilla basiconica, almost all bearing an apical pore. Three sen silla styloconica, two with an apical peg, and two small inconspicious sensilla basiconica are located on the galea. Possible function of these sensilla is discussed on the basis of studies on the closely related sister-group of Lepidoptera.

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

An important aspect of the association of Lype phaeopa (Stephens) with submerged wood is the oviposition behavior of adult females, which preferably oviposit their eggs on moist emergent or submerged parts of woody debris with a structured surface. The eggs are commonly deposited in cracks and crevices using the elongated ovipositor. Ovipositor morphology and various sensilla on the tip and along the ovipositor were studied by scanning electron microscopy and their possible function discussed. Structure of these sensilla and pre-oviposition behavior of the females point to a preference for certain oviposition sites on woody debris. This may be a key factor for the distribution and development of the larvae.

Previous investigations of interactions between aquatic invertebrates and decomposing wood substrates used wood decay classification systems based on external characteristics such as texture, shape, and color. These methods may be inaccurate for the assessment of wood decay because external appearance does not necessarily represent the physical state of decomposing wood. We tested an alternative method based on relative wood density adapted from terrestrial wood decomposition studies. We compared rating the physical condition of submerged twigs and branches by the loss of relative density to the traditional method based on external characteristics. Rating wood decay using loss of relative density showed distinct advantages compared to estimates by external characteristics. Measuring density delivered reproducible data independent of wood size or investigator bias. There was a correlation between decreases in relative wood density and increasing water content. In contrast, maximum water content was not correlated with the decay class rated by external characteristics. In addition, decay rating using external characteristics was influenced by the size of the woody debris. Rating wood decay using relative density is a simple and useful tool for characterizing woody debris in different stages of decay.