Relative Importance Of Insects Research Articles

The Diet of Nestling Abdim's Stork Ciconia abdimii in Niger

Although the Abdim's Stork (Ciconia abdimii) is a common breeder in the Sahel zone across Africa, its diet during the breeding season has never been studied. Chick meals were sampled in stork nests in West and Central Niger during early July and late August, representing early and mid rainy seasons in the area. The diet consisted of amphibians (Bufo sp.) and a range of insects with grasshoppers (Orthoptera) as the dominant (23 species) group making up 30% and 59% of prey biomass in July and August, respectively. In terms of frequency of occurrence, the important Sahelian pest species Oedaleus senegalensis was the most common grasshopper in the stork chick diet. There was a marked seasonal difference in the relative importance of insects and vertebrates: in July amphibians made up 61% of diet by wet weight, and insects 38%, while in August insects made up 92% of prey wet weight, and amphibians only 6%. The high dependency on amphibians in July was a surprise, but suggests that toads may be the key prey for the adult storks during the incubation period when toads become active while major new insect generations have not yet emerged. The increased importance of insects later in the rainy season reflects the emergence of new generations of grasshoppers, where, in particular, the locally (too) abundant Oedaleus senegalensis becomes the main prey.

Breeding system and spatial variation in the pollination biology of the heterocarpic Thymelaea velutina (Thymelaeaceae)

Thymelaea velutina (Thymelaeaceae) is a unique dioecious and heterocarpic shrub, each female producing both dry and fleshy fruits. It is endemic to the Balearic Islands (western Mediterranean) and has suffered an important regression in recent decades, especially due to habitat loss. It lives in coastal areas, mainly in dunes, but a few populations occur up to 1300 m in the mountains of Mallorca. In the present study, we examined its breeding system and pollen vectors, determined whether seed production is pollen-limited, and quantified the relative importance of different insect visitors at coastal and mountain sites. Selective exclusions showed no differences between populations in the relative importance of insects and wind as pollen vectors. Pollen was limiting at both populations, though not consistently in time. Flowers of T. velutina were visited mostly by generalist insects, and species composition and abundance of flower visitors varied both in space and time. The flowering period is about a month later in the mountain than in the dune, and this results in a higher frequency of insect visits to plants in the mountain due to the higher insect abundance; insects were also more diverse in the mountain, although they visited a proportionally lower number of flowers than in the dune. Despite this spatio-temporal variation in the frequency of insect visits and in the importance of a particular insect group, the ambophilous system in this species (previously described as anemophilous) ensures a relatively high fruit set at the two different sites.

Cost of crop losses in processing tomato and cabbage in southwestern Ontario due to insects, weeds and/or diseases

The relative importance of insects, weeds and diseases to yield losses in processing tomato (Lycopersicon esculentum Mill.) and cabbage (Brassica oleracea L. var. capitata L.) was measured by comparing yields in the presence and absence of appropriate control programs. In the absence of any pest control, average crop losses exceeded 80% in both crops. Average yield losses due to weeds alone approached 80% in processing tomato and 60% in cabbage. Insects alone did not significantly reduce yield of processing tomato in either year. In the absence of insect control, significant yield loss in cabbage approached 50% in only one year. When diseases were not controlled, yield of processing tomato declined significantly by nearly 30% in one trial. Failure to control disease had no significant impact on cabbage yield in this study. Monetary losses and costs of each management program were calculated. Key words: Tomato, cabbage, yield loss, insects, weeds, diseases

Entomophily of the cloudberry (Rubus chamaemorus)

AbstractCloudberry (Rubus chamaemorus L.), a dioecious perennial plant of boreal circumpolar distribution, is greatly prized for its berries. We crossed two treatments, pollinator exclusion and supplementary hand‐pollination, to determine i) the relative importance of insects as pollinators, ii) if pollinator activity was a limiting factor for the sexual reproduction of the plant, and iii) the relative contribution of diurnal vs. nocturnal visitors to pollination. The activity of natural pollinators resulted in 97.5 and 88.5% fruit set, along with 76.7 and 62.5% seed set in 1998 and 1999, respectively. When insects were excluded, fruit‐set dropped significantly to 18.4 (1998) and 12.8% (1999) and seed‐set to 5.4 (1998) and 5.0% (1999) showing the importance of mid‐ and large‐sized insects as pollinators. Natural levels of insect activity were sufficient to ensure complete pollination in both years as supplementary hand‐pollination did not significantly increase either parameter in plots where pollinators had free access. Nocturnal insects may serve as pollinators (fruit‐set = 41%), although they were less effective than diurnal pollinators (fruit‐set = 93%).