Zum Energieumsatz phytophager insekten im Buchenwald. I

Abstract

The energy turnover of weevil populations ofRhynchaenus fagi L.,Strophosomus (Schönherr) andOtiorrhynchus singularis L. (Curculionidae) was investigated in the following stages: a) Observation of habits and life-cycle; b) investigation of abundance-dynamics; c) establishing the energy budget of average individuals; d) calculation of the energy turnover of the populations. In the case ofRhynchaenus fagi the investigations were carried out with all developmental and maturity stages, in the cases ofStrophosomus sp. andO. singularis only with the imagimes. 1. The larva ofR. fagi mines the beechleaf. The development takes 5\2-6 weeks from oviposition (beginning of May) to the emergence of the beetle. The imago lives for about 12 months. There is a first eating period lasting until the end of July, followed by about 9 months of almost no food consumption; after hibernation there is the second eating period (May to June) and reproduction (beginning of May). Strophosomus sp. emerges on the ground in September and eats in the top shoots of the trees till the leaves fall; it feeds on fallen foliage on the ground during the winter and high in the trees again from May to July.Strophosomus sp. reproduces mainly parthenogenetically and dies no later than the end of August. O. singularis emerges mainly in May and June. After an intensive feeding period these females also deposit mostly unfertilized eggs. The beetles live for several years, imagines from different years living side by side. 2. Beginning in JulyR. fagi migrates increasingly to nearby spruce forests which are its favourite winter quarters in the Solling. Microclimate and thigmotaxis between the needles protectR. fagi from higher mortality. 3. Abundance and mortality of eggs, larvae, pupae and young beetles ofR. fagi were determined by counting the larvae and pupae on a large number of leaves and by marking leaves with a numbered label. For the beetles a linear progression of mortality was assumed from emergence to reproduction. In the case ofStrophosomus sp. the numbers of beetles emerging and the winter mortality were determined by means of eclector catches. Shaking samples yielded data concerning the mortality after hibernation. WithO. singularis the numbers of beetles emerging was established by means of eclectors. 4. In the case ofR. fagi the production of an average individual is 2.654 cal till the end of the pupal stage, 6.353 cal until death. 1.103 cal are taken up for cocoon and exuviae, 0.809 cal for egg production. From emergence to the end of July of the following yearStrophosomus sp. produces body substance of a calorific value of 28.630 cal, of which 9.690 cal are taken up for eggs. 5. A new calorimetric method was applied for the first time in determining the respiration ofR. fagi during its leaf-mining stages. The results agreed with the calculation of energy losses based on manometric measurement of O-consumption. With all weevil imagines manometric measurement of O-consumption was carried out under near-natural conditions. The imagines showed seas...

Morphology of the larvae of three Central European Strophosoma Billberg, 1820 (Coleoptera, Curculionidae, Entiminae) species

“…The data about the development of Strophosoma melanogrammum and S. capitatum (in part) have been mainly worked out and summarized by Grimm (1973) and Schauermann (1973). According to these sources both species develop in the Solling Mountains in the southern part of Niedersachsen (Germany) very similarly, and over a period of more than one year.…”

“…The eggs are usually laid in clusters in any kind of sheltered situations, e.g. in cracks of cork, between dry leaves of litter, in soil (probably in crevices), between leaf or flower buds of the host plant, on the ground in needles of pine shoots (Breese 1948;Grimm 1973) and, in the laboratory, between rolled or pleated absorbent paper or between paper and the substrate. The eggs are held together by a viscid fluid.…”

Feeding by short‐snouted weevils on seedlings of seven tree species planted beneath Norway spruce at differing stand densities

“…and related species, may damage seedlings during reforestation and in young conifer plantations with the purpose of producing Christmas decorations (Löf, 2000; Löf et al , 2004; Nielsen et al , 2006). The feeding behaviour of short‐snouted weevils and the resulting damage to seedlings has been described by several researchers (Grimm, 1973; Schauermann, 1973; Ehnström, 1985; Palm, 1996; Urban, 1999). Short‐snouted weevils mainly focus on needles and leaves when feeding on seedlings above ground, but they also frequently damage buds and young shoots, especially of broadleaved seedlings.…”