ABSTRACT
Background & objectives: A longitudinal study was carried out to investigate the species composition, seasonal abundance, parity and feeding preference of indoor sampled mosquitoes in Abeokuta, south-western Nigeria. Methods: The mosquitoes were sampled weekly from five stratified locations using Center for Disease Control (CDC) light-traps between August 2005 and July 2006. The mosquitoes were examined for abdominal condition and dissected for age composition. Microscopic and precipitin techniques were also employed for the determination of host blood source. Results: A total of 2969 mosquitoes which belong to 10 species of mosquitoes were collected during the study period. Mansonia africana (35.65%) constituted the most abundant species followed by Culex quinquefasciatus (32.23%) and Anopheles gambiae complex (13.52%). Other species in decreasing order of abundance were Coquilletidia maculipennis (8.2%), Aedes albopictus (5.9%), Ae. aegypti (1.93%), M. uniformis (1.81%), Cx. duttoni (0.25%), Cx. tigripes (0.25%) and An. funestus (0.25%). Seasonal abundance revealed a significant difference (p <0.05) in the population of mosquito vectors collected during the wet season as compared to the dry season and their abundance was positively correlated with rainfall. The results showed that the majority of the vector species collected were unfed and nulliparous. Moreover, the blood meal test was positive for human blood. Conclusion: The preponderance of mosquitoes observed in the study is of public health concern since they serve as vectors of most tropical diseases including malaria.
ABSTRACT
The volume of secretion obtained from adult Zonocerus variegatus (Orthoptera: Pyrgomorphidae) was influenced by the type of food plants. Insects fed on leaves of cassava Manihot esculenta, bitter leaves Vernonia amygdalina, and a mixture of M. esculenta and Acalypha wilkesiana gave a good volume of secretion while Chromolaena odorata, Elaeis guinensis, Aspilia africana and Citrus sinensis did not favour secretion production. No significant difference was recorded in the volume of secretion obtained from Z. variegatus from the two seasons irrespective of the food plant. Similarly, food plants gave no significant difference on the volume of secretion between the two seasons.
Subject(s)
Animals , Scent Glands , Orthoptera/physiology , PlantsABSTRACT
The odours of the whole body and the secretion of Zonocerus variegatus were easily recognised and perceived by human volunteers. However, the secretion odour is not related to the odour of the food plant consumed by the grasshopper. The repellency of Z. variegatus becomes more pronounced in the 6th. and adult instars whose gland lumens contain an appreciable volume of secretion. The secretion odour is so strong that even dilution does not affect its repulsiveness to humans. The secretion had pharmacological properties: it induced contraction in rat (Rattus rattus) stomach smooth muscle preparations and guinea pig (Cavia porcellus) ileum, and induced oedema formation in the rat hind paw. The secretion was not lethal to the animals used in this study, effects were temporary and recovery occurs after a short time.