Limited Differences in Insect Herbivory on Young White Spruce Growing in Small Open Plantations and under Natural Canopies in Boreal Mixed Forests.

In managed boreal forests, both plantations and natural regeneration are used to re-establish a cohort of conifer trees following harvest or disturbance. Young trees in open plantations generally grow more rapidly than under forest canopies, but more rapid growth could be compromised by greater insect damage. We compared insect damage on white spruce ( (Moench) Voss, Pinaceae) growing in plantations with naturally regenerated trees under mature forest canopies in boreal forests (Québec, Canada).

Defensive Traits during White Spruce () Leaf Ontogeny.

Changes during leaf ontogeny affect palatability to herbivores, such that many insects, including the eastern spruce budworm ( (Clem.)), are specialist feeders on growing conifer leaves and buds. Developmental constraints imply lower toughness in developing foliage, and optimal defense theory predicts higher investment in chemical defense in these vulnerable yet valuable developing leaves.

Improved performance of the eastern spruce budworm on black spruce as warming temperatures disrupt phenological defences.

Phenological shifts, induced by global warming, can lead to mismatch between closely interacting species. The eastern spruce budworm, Choristoneura fumiferana, an important outbreaking insect defoliator in North America, mainly feeds on balsam fir, Abies balsamea, which has historically been well synchronized with the insect. But as climate change pushes the northern range limit of the budworm further north into the boreal forest, the highly valuable black spruce, Picea mariana, historically protected against the budworm by its late budburst phenology, is suffering increased defoliation during the current outbreak.

Ontogenetic shift from aposematism and gregariousness to crypsis in a Romaleid grasshopper.

Traits of chemically-defended animals can change as an individual grows and matures, and both theoretical and empirical evidence favour a direction of change from crypsis to aposematism. This study examines the suite of traits involved in an unusual opposite shift from aposematism to crypsis in a neotropical toxic-plant-feeding Romaleid grasshopper, Chromacris psittacus (Gerstaecker, 1873). Field surveys, behavioural observations and a rearing experiment compare host plant choice, aggregation, locomotion and thermoregulation between life history stages.

Top-down and bottom-up controls on an herbivore on a native and introduced plant in a tropical agricultural landscape.

The recent introduction in a tropical agricultural environment of a weedy open-habitat plant () and subsequent host range expansion of a common forest-edge butterfly () onto that plant provides an opportunity to examine reconfiguration of tritrophic networks in human-impacted landscapes. The objectives of this study were (1) determine if the caterpillars on the exotic host are more or less limited by plant defenses (bottom-up forces) and if they experience enemy release (decrease of top-down pressure) and (2) define how anthropic open pasture habitat influences the herbivore's tritrophic niche. Field and laboratory monitoring of larval survival and performance on a native () host plant and the exotic () host plant were conducted in the Mindo Valley, Ecuador.

Detoxification of host plant phenolic aglycones by the spruce budworm.

This study examines the post-ingestive fate of two host-plant derived small-molecule phenolics (the acetophenones piceol and pungenol) that have previously been shown to be toxic to the outbreaking forest pest, spruce budworm (Choristoneura fumiferana). We test first whether these compounds are transformed during passage through the midgut, and second whether the budworm upregulates activity of the detoxification enzyme glutathione-s-transferase (GST) in response to feeding on these compounds. Insects were reared on either foliage or artificial diet to the fourth instar, when they were transferred individually to one of two treatment diets, either control or phenolic-laced, for approximately 10 days, after which midguts were dissected out and used for Bradford soluble protein and GST enzyme activity analysis.

How does synchrony with host plant affect the performance of an outbreaking insect defoliator?

Phenological mismatch has been proposed as a key mechanism by which climate change can increase the severity of insect outbreaks. Spruce budworm (Choristoneura fumiferana) is a serious defoliator of North American conifers that feeds on buds in the early spring. Black spruce (Picea mariana) has traditionally been considered a poor-quality host plant since its buds open later than those of the preferred host, balsam fir (Abies balsamea).

Spruce budworm feeding and oviposition are stimulated by monoterpenes in white spruce epicuticular waxes.

Monoterpenes, source of the distinctive odor of conifers, are generally considered plant defensive compounds. However, they are also known to act as long-range insect attractants, as they are volatile and permeate forest airspaces. Moreover, they are lipid soluble and can be absorbed into plant epicuticular waxes.

Butterflies of the high-altitude Atacama Desert: habitat use and conservation.

The butterfly fauna of the high-altitude desert of Northern Chile, though depauperate, shows high endemism, is poorly known and is of considerable conservation concern. This study surveys butterflies along the Andean slope between 2400 and 5000 m asl (prepuna, puna and Andean steppe habitats) as well as in high and low-altitude wetlands and in the neoriparian vegetation of agricultural sites. We also include historical sightings from museum records.

Rapid behavioural gregarization in the desert locust, Schistocerca gregaria entails synchronous changes in both activity and attraction to conspecifics.

Desert Locusts can change reversibly between solitarious and gregarious phases, which differ considerably in behaviour, morphology and physiology. The two phases show many behavioural differences including both overall levels of activity and the degree to which they are attracted or repulsed by conspecifics. Solitarious locusts perform infrequent bouts of locomotion characterised by a slow walking pace, groom infrequently and actively avoid other locusts.

Plasticity of collective behavior in a nomadic early spring folivore.

Collective behavior in the forest tent caterpillar (Malacosoma disstria) meets the thermal constraints of being an early spring folivore, but introduces other constraints in food choice. These are minimized by state-dependent, inter-individual, and ontogenetic variations in responses to social cues. Forest tent caterpillars use pheromone trails and tactile communication among colony members to stay together during foraging.

Effects of polymorphic melanism and larval diet on life history traits of Malacosoma disstria moths.

In this study we investigated the presence and possible genetic basis of polymorphic melanism in the forest tent caterpillar (Malacosoma disstria) moth. Adult moths were classified into pattern-based phenotypes and wing darkness was measured to quantify the degree of melanization. We found that two distinct phenotypes, melanic and simple, are present in these moths.

Defensive responses by a social caterpillar are tailored to different predators and change with larval instar and group size.

Gregariousness in animals is widely accepted as a behavioral adaptation for protection from predation. However, predation risk and the effectiveness of a prey's defense can be a function of several other factors, including predator species and prey size or age. The objective of this study was to determine if the gregarious habit of Malacosoma disstria caterpillars is advantageous against invertebrate natural enemies, and whether it is through dilution or cooperative defenses.

Larval nutrition affects life history traits in a capital breeding moth.

Fitness depends not only on resource uptake but also on the allocation of these resources to various life history functions. This study explores the life-history consequences of larval diet in terms not only of larval performance but also of adult body composition and reproductive traits in the forest tent caterpillar (Malacosoma disstria Hübner). Caterpillars were reared on their preferred tree host, trembling aspen (Populus tremuloides), or on one of three artificial foods: high protein:low carbohydrate, equal protein-to-carbohydrate ratio or low protein:high carbohydrate.

Influence of dietary nutritional composition on caterpillar salivary enzyme activity.

Caterpillars are faced with nutritional challenges when feeding on plants. In addition to harmful secondary metabolites and protein- and water-limitations, tissues may be carbohydrate-rich which may attenuate optimal caterpillar performance. Therefore, caterpillars have multiple strategies to cope with surplus carbohydrates.

Do food protein and carbohydrate content influence the pattern of feeding and the tendency to explore of forest tent caterpillars?

This study examines whether the ratio of protein to carbohydrate affects the timing of meals and the propensity to explore of forest tent caterpillars (Malacosoma disstria). The behavior of fourth instar caterpillars was observed on three semi-defined artificial diets varying in protein (p)-carbohydrate (c) ratio. These diets were (a) p14:c28, (b) p28:c14, and (c) p35:c7.

Resource distribution mediates synchronization of physiological rhythms in locust groups.

Synchronized behaviour is common in animal groups. In ant colonies, synchronization occurs because active ants stimulate their neighbours to activity. We use oscillator theory to explain how stimulation from active neighbours synchronizes activity in groups of solitarious locusts via entrainment of internal physiological rhythms.

How well do specialist feeders regulate nutrient intake? Evidence from a gregarious tree-feeding caterpillar.

Nutritional regulation is a powerful mechanism used by generalist feeders to obtain the balance of nutrients they require from nutritionally diverse, perhaps unbalanced, foods. We examined nutritional regulation in a species with a narrow individual diet breadth: the forest tent caterpillar, Malacosoma disstria. Fourth instar caterpillars were provided with artificial foods consisting of different ratios of protein to digestible carbohydrate in no-choice, choice and compensatory feeding experiments.

Mechanosensory-induced behavioural gregarization in the desert locust Schistocerca gregaria.

Desert locusts show an extreme form of phenotypic plasticity, changing between a cryptic solitarious phase and a swarming gregarious phase that differ in many aspects of behaviour, physiology and appearance. Solitarious locusts show rapid behavioural phase change in response to tactile stimulation directed to the hind femora. Repeatedly touching as little as one quarter of the anterior (outer) surface area of a hind femur produced full behavioural gregarization within 4 h.