Cues for shelter use in a phytophagous insect

Many insects spend a large proportion of their life inactive, often hiding in shelters. The presence of shelters may, therefore, influence where insects feed. This study examines stimuli affecting the use of shelters by adults of the pine weevil, Hylobius abietis (L.) (Coleoptera, Curculionidae). This species is an economically important forest pest in Europe since the adults feed on the stem bark of newly planted conifer seedlings. When there are hiding or burrowing places present in close proximity to a seedling, pine weevils may hide there and repeatedly return to feed on the same seedling. Experiments were conducted in a laboratory arena with above-ground or below-ground shelters and in the presence or absence of wind. Pine weevils were highly attracted to shelters both above and below ground. Weevils in shelters were often observed assuming a characteristic "resting" posture. Experiments with opaque and transparent shelters showed that visual stimuli are used for orientation towards shelters and also increase the probability of an individual remaining in a shelter. The presence of wind increased the weevils' propensity to use shelters both above and below ground. The present study indicates that shelters have a major influence on the behavior of the pine weevil and possible implications of the results are discussed

Erroneous conclusions about current geographical distribution and future expansion of forest insects in Northern Sweden: comments on Hof and Svahlin (2015)

We question the validity of the results and the conclusions from a study entitled The potential effect of climate change on the geographical distribution of insect pest species in the Swedish boreal forest that was recently published in Scandinavian Journal of Forest Research. The main problem is that for several of the species the current geographical distributions presented in the paper (based on modeling of a limited set of occurrence data) are vastly underestimated compared with distribution maps in standard reference literature and other available occurrence data. As a consequence of that the predicted major future range expansions of these important pest species are also erroneous

Snytbaggen

Barrträdsplantor som planterats efter avverkning blir ofta dödade av snytbaggens gnag. Men genom olika åtgärder kan skadorna minskas till en acceptabel nivå. Vilka metoder du bör välja beror bland annat på var i landet hygget ligger. Denna broschyr syftar till att förklara vilken effekt på plantskadorna olika åtgärder ger och hur de kan kombineras i olika delar av Sverige

The structure of feeding behavior in a phytophagous insect (Hylobius abietis)

Analysis of the feeding behavior of animals using such a high temporal resolution that meals can be defined may improve our understanding of the mechanisms regulating feeding. Meals can be distinguished in an ethologically meaningful manner by using the ‘meal criterion’, the shortest non-feeding interval between feeding bouts recognized as meals. However, such a criterion has only been determined for a few insect species. Applying a recent method developed for assessing meal criteria for vertebrates, we determined the meal criterion for Hylobius abietis (L.) (Coleoptera: Curculionidae) based on data from video recordings of single individuals feeding on seedlings of Norway spruce, Picea abies (L.) Karst. (Pinaceae). The pine weevil is an economically important pest insect because it feeds on the stem bark of planted conifer seedlings. Weevils had 4-5 meals per day. Each meal lasted about 24 min during which about 13 mm2 of bark per meal were removed. Females had longer total meal durations and longer non-feeding intervals within meals than males. Girdling seedlings did not affect the weevils’ feeding properties. The size of meals was significantly correlated to the duration of non-feeding intervals before and after them. This study is one of few describing the feeding behavior of an insect at a temporal resolution that allows individual meals to be distinguished. With more meal-related data from insects available, differences in meal properties may be interpreted based on phylogeny, ecology, and physiology. Our results may also assist in the setup and interpretation of studies of plant-insect interactions, and facilitate the evaluation and development of methods to protect plants against herbivores

Diel behaviour and time budget of the adult pine weevil, Hylobius abietis

The pine weevil (Hylobius abietis (L.); Coleoptera: Curculionidae) has a high economic impact on forest regeneration in Europe. The general biology of the pine weevil has received considerable attention, but there is insufficient knowledge about its diel behaviour and time budget. Therefore, the feeding and locomotion behaviour of individual adult weevils on Norway spruce (Picea abies (L.) Karst.) seedlings is observed for 24 hour-periods in the laboratory. Both girdled and non-girdled seedlings are used to assess how the weevils’ behaviour is influenced by the plants physiological response to the girdling. The locomotion pattern shows a distinct maximum during the beginning of the dark phase whereas most feeding occurs during the second half of the dark phase and the first hours of the subsequent light phase. The girdling treatment increase the time that weevils spend on the seedlings during the first part of an observation session, but has no effect on their feeding pattern. The weevils’ time budgets on girdled and non-girdled seedlings are similar. On average, they spend 34 % of their time in locomotion and 6 % on feeding. Females spend more time feeding than males (7.1 % vs. 4.2 %), possibly because they have higher food requirements, e.g. for egg production. Females also spend more time in total on the seedlings than males (26.3 % vs. 7.0 %). This study reveals, in high temporal resolution, the diel feeding and locomotion behaviour and time budget of male and female pine weevils