Influence of insecticide treatments on ant-hemiptera associations in tropical plantations.

In this survey conducted in southern Cameroon, we compared ant-Hemiptera associations on plantations treated with insecticides, on plantations 2 years after insecticide treatments ceased, and on control lots that never received insecticide treatments. By eliminating arboreal-nesting ants, insecticides favored the presence of "ecologically dominant" ground-nesting, arboreal-foraging species that occupied the tree crowns. The reinstallation of arboreal ants was slow as 2 yr after insecticide treatment ceased differences with the control lots were significant. This intermediary period also illustrated that arboreal ants can found and develop colonies on trees occupied by ground-nesting species. Certain arboreal species were more frequent during this intermediary period than on the control lots, showing that the period of installation in the trees was followed by competition between arboreal ants. We confirm that ground-nesting ants tend a wide range of hemipteran families, including well known agricultural pests, whereas arboreal ants, particularly dominant species, were mostly associated with Coccidae and Stictococcidae that do not pose problems to the supporting trees. A tree effect was also noted for both ant and hemipteran distribution. We concluded that because of insecticide use, ground-nesting ants pose problems through their associated Hemiptera. On the contrary, dominant arboreal ants, strong predators, benefit their supporting trees by excluding ground-nesting species and tending mostly nonpest Hemiptera. Nevertheless, certain of them, carpenter species or species likely to tend Pseudococcidae, have to be eliminated through integrated management.

[Blood lipid and apolipoprotein concentrations in a healthy urban population of Northern Cameroon: variation with age and sex]. / Concentration des lipides et apolipoprotéines sériques dans une population urbaine saine du Nord-Cameroun: variation selon l'âge et le sexe.

We determined plasma lipids and apolipoproteins A-I and B in 142 subjects from Ngaoundere, in the north of Cameroon, as a means of evaluating atherosclerotic risks. The mean triglyceride concentration was 0.836 +/- 0.174 g/l; mean total cholesterol concentration was 1.276 +/- 0.251; mean HDL cholesterol concentration was 0.162 +/- 0.222; mean apolipoprotein A-I concentration was 0.577 +/- 0.096 and mean apolipoprotein B concentration was 0.836 +/- 0.174. These values differ from those reported for Caucasian populations but are similar to those reported in other studies in Cameroon. All lipid factors except HDL cholesterol concentration increased significantly with age (p < 0. 05). There were also differences between the sexes, with mean triglyceride, LDL cholesterol, HDL cholesterol and apolipoprotein B concentrations significantly higher (p < 0.01) in men than in women. There was no significant difference between the sexes, however, in total cholesterol and apolipoprotein A-I concentrations. Thus advanced age and being male are risk factors for atherosclerosis in this population.