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The African root and tuber scale Stictococcus vayssierei Richard is the only known hypogeal species of the family Stictococcidae. Its wide range of host plants together with concurrently field observed differences in host preference provided evidence of polyphagy or the involvement of more than a single-scale species. To establish the baseline information for future taxonomic studies, newly emerged larvae were collected from infested cassava from three sites in the humid forest zone of southern Cameroon. A glass binocular magnifier was used to observe morphological changes of live individuals and slide-mounted individuals of all developmental stages were examined with a compound microscope. Stictococcus vayssierei females went through three developmental stages-two larval instars and an adult stage. The first and second instars were purple-red, while the adult was brown. Body size and the degree of sclerotization of the dorsal line increased in each developmental stage. White waxy secretions on the basal periphery of the second instar, and both dorsum and periphery of the adults, distinguished them from the first instar, which lacks the white waxy secretions. On slide-mounted specimens, certain aspects of the anal complex (i.e. number of opercular plates and -setae) were found to be the most discriminating features of S. vayssierei life stages. These results are useful for further studies on the diversity of subterranean stictoccocid scales.Résumé. La cochenille Africaine des plantes à racines et tubercules Stictococcus vayssierei Richard est l'unique espèce souterraine décrite appartenant à la famille des Stictococcidae. La large gamme des plantes attaquées ainsi que les différences de préférence observées suggèrent l'implication de plus d'une espèce de cochenille hypogée. Pour réunir des informations de base pouvant permettre une prochaine étude taxinomique, des larves femelles nouvellement pondues ont été collectées sur des tiges de manioc infestées provenant de trois localités de la région de forêt humide du sud Cameroun. Les changements morphologiques pendant le développement ont été observés à l'aide d'une *loupe binoculaire et d'un microscope après montage entre lames et lamelles des échantillons de chaque stade de développement. Le développement des femelles de S. vayssierei passe par trois stades dont deux stades larvaires et un stade adulte. Le premier et le deuxième stade sont de couleur rouge pourpre alors que le troisième est de couleur marron. En plus de l'augmentation de la taille, on constate au cours du développement la sclérotisation de l'anneau anal et de la ligne dorsale. On note également la présence de sécrétions cireuses blanchâtres près de la périphérie basale du deuxième stade et sur la cuticule dorsale du troisième stade, ce qui les distingue du premier stade qui ne présente pas de sécrétions cireuses blanchâtres. Cependant, sur les échantillons montés entre lames et lamelles, il apparaît que le nombre de plaques et de soies operculaires présentes sur le complexe anal sont les caractères...

Extrafloral nectaries (EFNs) and hemipteran honeydew are often discussed as two alternative mechanisms encouraging ant visitation in mutualistic ant-plant relationships, but little is known about the processes that generate distribution pattern in species-rich insect communities. A case study on the interaction between ants, EFNbearing plants and hemipterans was investigated along a gradient of increasing disturbance from regenerated forest to mixed crop field. Ants, EFN-bearing plants and hemipterans sampling was conducted in these vegetations during the wet and the dry seasons in five locations. Results showed that partitioning of ant species between season and vegetation was significantly different from random. High specialization index was observed in hemipterans/plants and ant/hemipterans interactions. Low specialization index was observed between ants and EFN-bearing plants mainly in the mixed crop field. Ant species were mostly found in non-aggressive co-occurrence at nectar sources. At the species level, specialization index was high for Anoplolepis tenella (0.86 ± 0.06) and also for its associated hemipterans Stictococcus vayssierei (0.97 ± 0.02). This association is detrimental to food crop especially cassava. These results outline the effect of vegetation and food source on the structure of the ant assemblage and interaction in tropical forest zone.

Stictococcus vayssierei is a major pest of root and tuber crops in central Africa. However, data on its ecology are lacking. Here we provide an updated estimate of its distribution with the aim of facilitating the sustainable control of its populations. Surveys conducted in nine countries encompassing 13 ecological regions around the Congo basin showed that African root and tuber scale was present in Cameroon, Central African Republic, Congo, Democratic Republic of Congo, Equatorial Guinea, Gabon and Uganda. It was not found on the sites surveyed in Chad and Nigeria. The pest occurred in the forest and the forest-savannah mosaic as well as in the savannah where it was never recorded before. However, prevalence was higher in the forest (43.1%) where cassava was the most infested crop, compared to the savannah (9.2%) where aroids (cocoyam and taro) were the most infested crops. In the forest habitat, the pest was prevalent in all but two ecological regions: the Congolian swamp forests and the Southern Congolian forest-savanna mosaic. In the savannah habitat, it was restricted to the moist savannah highlands and absent from dry savannahs. The scale was not observed below 277 m asl. Where present, the scale was frequently (87.1% of the sites) attended by the ant Anoplolepis tenella. High densities (>1000 scales per plant) were recorded along the Cameroon-Gabon border. Good regulatory measures within and between countries are required to control the exchange of plant materials and limit its spread. The study provides information for niche modeling and risk mapping.https://www.cambridge.org/core/terms. https://doi.