Abida Butt

Predatory potential of three hunting spiders inhabiting the rice ecosystems

Present study was designed to assess the prey preference behaviour of three most dominant hunting spiders [Lycosa terrestris Butt, Anwar and Tahir 2006 (Araneae: Lycosidae), Pardosa birmanica Siman 1884 (Araneae: Lycosidae) and Oxyopes javanus (Thorell 1887) (Araneae: Oxyopidae)] of rice ecosystems both in the laboratory and in the field. Two types of laboratory experiments, i.e., choice and no choice feeding, were performed using only adult male and female specimens of the spiders. No choice test showed that each of the three hunting spiders readily consumed larvae and nymphs of rice pests offered. Female hunting spiders consumed more prey compared to male hunting spiders. Results of choice feeding test indicated that L. terrestris and P. birmanica preferred nymphs of rice insect pests while O. javanus preferred larvae of rice insect pests. Results of direct observations showed that in August, dipterous insects were the most numerous rice pests consumed by L. terrestris, P. birmanica and O. javanus, comprising over 56.3, 38 and 48% of their respective diets. In contrast, in September, the proportion of dipterous insects decreased dramatically and hoppers become the most numerous pests, comprising over 50, 51 and 41% of all prey and spiders consumed by L. terrestris, P. birmanica and O. javanus, respectively. In October, aquatic Heteroptera were frequently observed in their diets. Predatory potential of these hunting spiders differed statistically in the laboratory as well as in the field. It is concluded from the results of present project that studied species of spiders could successfully be used to control insect pests of rice ecosystems.

Foraging strategies and diet composition of two orb web spiders in rice ecosystems

Abstract We conducted a field study in September 2007 and 2008 to analyze the foraging activity, natural diets, and predatory efficacy of Tetragnatha javana (Thorell 1890) (Araneae: Tetragnathidae) and Neoscona theis (Walckenaer 1842) (Araneae: Araneidae) on selected prey. The relationship between body measurements (carapace width, leg length, total body length, and body weight) and web dimensions (capture area, capture thread length, number of radii, number of spirals, and mesh height) of both species was also investigated. Most of the observed T. javana constructed their webs between two adjacent rice plants, while N. theis placed theirs at the top of rice plants. Both species required approximately an hour to complete a web, which differed significantly from each other in height, diameter, and capture area. Both species constructed only a single web per day. Web building activity of both species was intense from 17:00 to 18:00, while prey-handling activity was high from 19:00 to 20:00. In both species, peaks of feeding were recorded just after the peaks of prey handling (21:00). The main prey orders caught in the webs of both species were Lepidoptera, Diptera, Homoptera, Coleoptera, Hymenoptera, and Orthoptera. The time required to reach and capture lepidopteran (adults of stem borer and leaf folder) and homopteran prey was similar for both species. However, the time required to reach and capture orthopteran (grasshopper nymphs) prey was significantly longer for T. javana than for N. theis. Capture area increased with carapace width, and capture thread length increased with carapace width and body weight, while leg length and body length did not relate to either of these web variables. The number of radii, number of spirals, and mesh height did not correlate with any of the body size measurements. We concluded that both species can be used effectively to reduce insect pests of rice fields.

Genetic diversity in cytochrome c oxidase I gene of Anopheles mosquitoes

Abstract Genetic diversity in cytochrome c oxidase I (coxI) among 7 species of Anopheles mosquitoes from Pakistan, and 37 species from different geographical regions of the world, was recorded. Automatic Barcode Gap Discovery (ABGD) analysis revealed a clear gap between intraspecific and interspecific distances of 7 species from Pakistan. However, genetic distances of 37 Anopheles species failed to adequately differentiate species in a global context. Intraspecific and interspecific divergences for 7 Anopheles species of Pakistan varied from 0.0% to 2.5% (mean = 0.49%) and 8% to 22.3% (mean = 12.77%), respectively. Similarly, intraspecific distances for 37 species from different parts of world ranged from 0.0% to 11.2% (mean = 0.65%) while values of interspecific divergences ranged from 3.4% to 35% (mean = 11.75%). Although phylogenetic tree revealed separate clades for 7 Anopheles species of Pakistan, it failed to produce separate clades for 37 species of the world. It is concluded that although standard barcode region is helpful for identifying Anopheles mosquitoes, combination of multi-locus approaches and morphology may be required to accurately identify species in this genus.

Effect of different agricultural practices on spiders and their prey populations in small wheat fields

Abstract The influence of different agricultural practices (viz., edge crop, zero tillage sowing and low input of fertilizers) on the density and diversity of spider populations of small wheat fields present in close vicinity were compared in experiments conducted from 2007–2009. The study was conducted in district Sheikhupura, Punjab province, Pakistan. Five fields with different management activities were sampled for spiders using pitfall traps and a visual search method. A total of 23,097 specimens of spiders belonging to 47 species, 21 genera and 12 families were recorded during the study. There was a difference in the density and richness of spiders and high density was recorded in the zero-tillage sown fields and lowest in low-input fields. However, the diversity and evenness did not differ with the habitat types. The analysis of agrobiont species distribution showed that hunting spiders were abundant in zero-tillage sown wheat and orb webs in wheat fields edged with Brassica napus crop. Density of spiders in fields was associated with aphid and collembolan density. Based on this study we can suggest that diversification of management activities can be helpful to maintain spider diversity in the crop which can be helpful in pest management activities.

A study of web structure of Neoscona theisi (Araneae: Araneidae) under field conditions

Abstract Present study was designed to record variation in the web parameters (mesh size, capture thread length, capture area, symmetry, and height) of adults and young Neoscona theisi constructed in natural conditions. Relationships of studied web parameters with several body measures (carapace width, IV leg length, and body mass) were also assessed. Data showed that webs constructed by adult spiders have larger capture area, capture thread length (CTL), and mesh size. Body mass was the important body measures to describe variations in capture area, CTL, and mesh size. Carapace width also influenced CTL and asymmetry of the web. However, studied body measures were not the predictors of web height above ground. From this study, it was concluded that variations in web design of N. theisi is affected by body mass and carapace width of the spider which may be helpful to estimate their biological control potential in different agroecosystems.