Survival and behaviour of unfed stages of the ticksRhipicephalus appendiculatus,Boophilus decoloratus andB. microplus under field conditions in Zimbabwe

The survival and behaviour of the unfed stages ofRhipicephalus appendiculatus, Boophilus decoloratus andB. microplus in gauze columns were observed in long and short grass in the highveld of Zimbabwe. Ticks were exposed in the cool, hot and rainy seasons of 1980 and 1981. All species and stages survived longer in long grass than in short grass. Larvae from engorged female ticks released in the cool season hatched much later than incubator-reared controls. They were consequently not present during the cold weather and survived longer than larvae subjected to the low temperatures, in which the shortest survival-times were recorded. The survival of nymphs was insensitive to season. The longest survival-times were recorded in adults. Median survival-times of incubator-reared adults ranged from 165 to 375 days in short grass and from 333 to 493 days in long grass. These times were usually longer than those for adults which moulted in the field. Larvae of the three species and nymphs ofR. appendiculatus were active soon after hatching or moulting, irrespective of the season. In contrast, adults ofR. appendiculatus showed different patterns of activity in different seasons. Adults first appeared at the base of the columns in October/November and then gradually ascended to reach a maximum height in December/January. They remained high up in the columns until May/June when the weather became increasingly cold and dry. Larvae ofB. decoloratus climbed higher up in the columns in the long grass than did the larvae of the other two species.Larvae and nymphs ofR. appendiculatus and larvae ofB. microplus migrated up and down the columns daily, but larvae ofB. decoloratus and adults ofR. appendiculatus did not migrate.     

Phylogeny and taxonomy of the Prenolepis genus‐group of ants (Hymenoptera: Formicidae)

Abstract. We investigated the phylogeny and taxonomy of the Prenolepis genus‐group, a clade of ants we define within the subfamily Formicinae comprising the genera Euprenolepis, Nylanderia, gen. rev. , Paraparatrechina, gen. rev. & stat. nov. , Paratrechina, Prenolepis and Pseudolasius. We inferred a phylogeny of the Prenolepis genus‐group using DNA sequence data from five genes (CAD, EF1αF1, EF1αF2, wingless and COI) sampled from 50 taxa. Based on the results of this phylogeny the taxonomy of the Prenolepis genus‐group was re‐examined. Paratrechina (broad sense) species segregated into three distinct, robust clades. Paratrechina longicornis represents a distinct lineage, a result consistent with morphological evidence; because this is the type species for the genus, Paratrechina is redefined as a monotypic genus. Two formerly synonymized subgenera, Nylanderia and Paraparatrechina, are raised to generic status in order to provide names for the other two clades. The majority of taxa formerly placed in Paratrechina, 133 species and subspecies, are transferred to Nylanderia, and 28 species and subspecies are transferred to Paraparatrechina. In addition, two species are transferred from Pseudolasius to Paraparatrechina and one species of Pseudolasius is transferred to Nylanderia. A morphological diagnosis for the worker caste of all six genera is provided, with a discussion of the morphological characters used to define each genus. Two genera, Prenolepis and Pseudolasius, were not recovered as monophyletic by the molecular data, and the implications of this result are discussed. A worker‐based key to the genera of the Prenolepis genus‐group is provided.     

Effects of netropsin on yeast mitochondria

Netropsin binds tightly to AT rich regions of DNA and correspondingly is an efficient inhibitor of mitochondrial DNA replication in $\text{Saccharomyces}\text{cerevisiae}$. Netropsin treatment does not cause formation of large populations of petite cells. However, a large portion of cells grown in cultures with ethanol as carbon source are killed by 1 μg/ml netropsin. When petite induction by berenil or ethidium bromide is carried out in the presence of netropsin, the petite cells are killed. This appears to be an effect of netropsin action on the cells during the process of petite formation.