ABSTRACT
Distribution pattern of animals, modification of their life cycle and behaviours have been governed by climatic changes. It affects the insect from egg to adults. Eggs always face lot of stress either from biotic or abiotic threats. This study examined the flooding of Dysdercus cingulatus eggs with seawater alone and in combination with fresh water on the egg hatchability, survival and development, fecundity and hatchability of the hatched nymphs and adults, respectively under laboratory conditions. Flooding of egg in salt water, slightly and insignificantly increased the nymphal developmental period (24.2 days) of the insect. However, treatment has no impact on the survival of nymphs (95.4%). Fecundity (135.2 eggs female-1), hatchability (77.51%) has been gradually decreased while the amount of sea water increased in the treated water. Results revealed that entering of seawater into the agriculture fields alter the reproduction of insects subsequently change the food web in the ecosystem.
ABSTRACT
Rhynocoris fuscipes is a potential predator of many economically important pests in India. In the present study, its venomous saliva (VS) was collected by milking and diluted with HPLC grade water to different concentrations (200, 400, 600, 800 and 1000 ppm). Microinjection of Rhynocoris fuscipes VS was more toxic than its oral administration in Helicoverpa armigera (cotton bollworm) and Spodoptera litura (tobacco cutworm). Thus, R. fuscipes VS was found to be toxic to third instar S. litura and H. armigera with respective LD50s of 846.35 and 861.60 ppm/larva at 96 hours after microinjection. The current results showed that VS of Rhynocoris fuscipes caused mortality of H. armigera and S. litura. Active peptides from VS may be isolated, identified and assessed for their impact in order to ascertain how they alter the physiology of these pests, information that could be applicable in pest management programs.(AU)
Subject(s)
Animals , Saliva , Pest Control , Spodoptera , Reduviidae , MortalityABSTRACT
The reduviid predators Rhynocoris marginatus (Fab.) and Catamirus brevipennis (Servile) use their venoms to paralyze their preys. We detected the antibacterial activity of R. marginatus and C. brevipennis venoms against seven Gram-negative and four Gram-positive bacteria by using the disc diffusion method. Rhynocoris marginatus venom exhibited antibacterial activity against four Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Salmonella typhimurium) and one Gram-positive (Streptococcus pyogenes). Catamirus brevipennis venom showed antibacterial activity against six Gram-negative (Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus vulgaris, and Salmonella typhimurium) and three Gram-positive (Bacillus subtilis, Staphylococcus aureus, and Bacillus sphaericus) bacteria. Both C. brevipennis (90.91%) and R. marginatus (45.45%) venoms were more effective against Gram-negative bacteria (80% and 70% for R. marginatus and C. brevipennis, respectively). The venoms of both reduviid predators are composed of low molecular weight proteins (7-33 kD).