1. Trees present herbivorous insects with the greatest diversity of resources of any plant growth form. Both ontogeny and shading can alter suitability for arboreal insect herbivores.2. We conducted a longitudinal study of tagged 'mature' (>12 months old) Eucalyptus camaldulensis leaves to compare the suitability of understorey and canopy trees for the leaf senescence-inducing psyllid, Cardiaspina albitextura. We quantified sugars and tannins as possible predictors of nymphal abundance.3. Canopy leaves hosted double the number of nymphs as understorey leaves. Variation among individual trees (understorey and canopy) was the most important source of heterogeneity explaining psyllid abundance, although relative leaf age significantly influenced oviposition on canopy leaves. The diversity of foliar sugars was higher among canopy leaves than among understorey leaves. There was significant between-tree diversity in total hydrolysable tannins (HTs) and total condensed tannins (CTs) among understorey trees but not among canopy trees. Heterogeneity among understorey and canopy trees was explained by greater diversity of ellagitannins (HTs) than of CTs. 4. Shading is detrimental to the survival of nymphs on both host types, but sugars are unlikely to explain variation in suitability. Vescalagin (an ellagitannin) was negatively correlated with the abundance of nymphs on both host types.

Insect herbivores assess plants by integrating responses elicited by a variety of external and internal cues and signals mediated by physical and chemical traits. We investigated host assessment behaviours of adult females of the Eucalyptus‐feeding psyllid, Glycaspis brimblecombei Moore (Hemiptera: Aphalaridae), on 10 species and subspecies (comprising preferred and non‐preferred hosts) using video recordings, electrical penetration graph (EPG) technology, and histological examination of tissues surrounding secondary veins. Our video recordings indicated that the shortest first searching time (mean 7.5 s) occurred on preferred hosts. Females placed on novel (non‐preferred) hosts jumped off leaves in <10 s. We found that host acceptance occurred surprisingly rapidly after stylet penetration, e.g., between 7 and 11 s on preferred eucalypts, suggesting a strong role for gustatory cues. Our histological studies provided no evidence of physical barriers to phloem access. Females produced eight EPG waveforms, as observed for other psyllids and aphids, but the durations of PG (xylem activity) and PE2 (phloem ingestion), in particular, were unlike those recorded for any other hemipteran. On preferred hosts, phloem ingestion represented 21.5% (mean duration 4 h 18 min) of individual feeding bouts, whereas on non‐preferred hosts, there was almost no ingestion from phloem. Xylem ingestion on non‐preferred hosts represented 20.1% (mean duration 4 h 1 min) of feeding bouts, presumably to imbibe water. Thus, contrary to widespread belief, female G. brimblecombei did not feed exclusively from phloem even on preferred hosts, but also regularly ingested from the xylem. This is surprising considering that nymphs construct lerps consisting of approximately 16% sugars, and suggests that adults feed from phloem for shorter periods than offspring. Rapid assessment of hosts could also mean that positive stimuli induced by sugars are opposed by negative gustatory stimuli experienced in non‐vascular tissues. The most likely source of such stimuli are water‐soluble polyphenolic compounds that are widespread in cell vacuoles.

Electricity industry is changing by organizational and legislative evolutions dealing with economical and environmental affairs. Besides rapid development in energy generation decreased the related variable costs, considering environmental issues. In this study energy generation technologies are evaluated both from economical and environmental views. Applying Analytical Hierarchy Process (AHP) which is extremely applicable and known as one of the efficient methods to analyze complicated multi criteria problems it is achieved interesting results from evaluation. The main goal of this evaluation which is presented in this essay is to extract total preference weights for generation technology. Total preference weights are determined considering four criteria in fossil fuel power plants and renewable energy resources power plant using this evaluation pattern. For three power plant of gas, steam and combine cycle the total preference weights are calculated by considering seven criteria. For the next eight power plants of wind, small hydro, photovoltaic, solar thermal, micro turbine, biomass, geothermal and fuel cell total preference weights is considered according to seven criteria. Optimum capacity is calculated and determined. Sensitivity analysis is made on two most important criteria of this model named 1-operation and investment cost, and 2-fossil resources scarcity for power plants. 1-Multiple criteria of objective function, 2-possibility of sensitivity analysis on criteria weights and 3-concurrent inspection of qualitative and quantitative criteria in optimization of objective function are three advantages of the proposed model comparing common applying method such as (mono-objective software WASP)