Egg masses of some stream‐dwelling caddisflies (Trichoptera: Hydrobiosidae) from Victoria, Australia

Abstract

Eggs are a largely neglected life stage in most ecological studies of aquatic insects, despite the importance of oviposition behaviour and fecundity estimates for many research questions. Incorporating egg stages into ecological research requires that ecologists can identify and quantify eggs, but descriptions of eggs and egg masses are scarce for many groups and particularly for Australian taxa. This paper focusses on stream-dwelling caddisflies in the family Hydrobiosidae and provides species-level identifications, morphological descriptions and images of egg masses of some species that commonly occur in south-eastern Australia. All the species we identified laid plaque-shaped egg masses attached to the underside of river rocks that protrude above the water surface. These egg masses can be identified in the field with the naked eye or the aid of a low-magnification hand lens. Interspecific variations in egg mass morphology were primarily thickness and firmness of the spumaline layer, egg mass size and arrangement of eggs within the mass. We also provide some ecological information on clutch sizes and the physical characteristics of oviposition sites, and we discuss various ways in which these taxa could be exploited as model systems for ecological research.

Variations in fecundity over catchment scales: Implications for caddisfly populations spanning a thermal gradient

“…However, available measures of body size (see Section 2) suggest no commensurate increase in the size of A. obliquum females to accommodate such a difference in egg numbers. It is possible that a larger range of body sizes (or forewing lengths) is required to detect between‐species patterns in clutch size and body size (Lancaster & Glaister, ).…”

“…We surveyed the clutch sizes of three species of caddisfly Ulmerochorema rubiconum , Apsilochorema gisbum , and Apsilochorema obliquum (family: Hydrobiosidae). Egg masses of these species are described by Reich () and Lancaster and Glaister (). All three species oviposit exclusively on emergent rocks (rocks that protrude from the water) making it easy to locate egg masses (Reich, ).…”

“…Hydrobiosidae). Egg masses of these species are described by Reich (2004) and Lancaster and Glaister (2018). All three species oviposit exclusively on emergent rocks (rocks that protrude from the water) making it easy to locate egg masses (Reich, 2002).…”

Terrestrial–aquatic transitions: Local abundances and movements of mature female caddisflies are related to oviposition habits but not flight capability

“…There are at least three distinctly different oviposition habits within this set of nine species. The five hydrobiosids and one hydropsychid, Cheumatopsyche AV3, lay their eggs as plaque‐shaped masses attached to the underside of emergent rocks in riffles (Lancaster & Glaister, ; Reich, ; Reich & Downes, ). The second hydropsychid, Asmicridea edwardsi , also oviposit plaque‐shaped masses attached to rocks in riffles, but on both submerged and emergent rocks (Reich, ).…”

“…For example, some species lay eggs on submerged rocks in pools (Deutsch, ; Lancaster, Downes, & Arnold, ), whereas others oviposit in riffles and primarily on rocks that protrude above the water surface, i.e. emergent rocks (Hoffmann & Resh, ; Lancaster et al, ; Lancaster & Glaister, ; Reich & Downes, ). However, numbers of such emergent rocks vary between riffles and there is often a correlation of oviposition site densities with egg mass densities, and sometime with larval densities also (Lancaster & Downes, , ).…”