Cohort studies on mosquito (Diptera: Culicidae) larvae living in the water-filled floral bracts of Heliconia aurea (Zingiberales: Musaceae)

Abstract. 1. An experimental and observational study of the three species of mosquito larvae living in the water-filled floral bracts of Heliconia aurea at Rancho Grande, Venezuela, was designed to determine if each mosquito species forms instar cohorts and excludes conspecifics of younger instars. This study was motivated by a statement of Maguire (1971) who suggested that mosquito larvae in Puerto Rican Heliconia inflorescences form instar cohorts and exclude younger mosquitoes from the floral bracts.
2. Field observations of naturally occurring populations of mosquito larvae from fifty-three H.aurea inflorescences give no indication that cohorts are formed for Wyeomyia felicia and Culex bihaicolus . However, there is strong evidence that cohorts of Trichoprosopon digitatum occur. These cohorts are not structured by larval competition but by female preference of the youngest bracts as oviposition sites and by large T.digitatum larvae feeding on smaller con-specifics.
3. Field experiments show that first instar W.felicia and C.bihaicolus survive as well over a 6 day period in the presence of third instar conspecifics as they do when all mosquito larvae in an experimental bract are first instars.     

Comparison of two sampling methods for domestic populations of Triatoma infestans in north-west Argentina

Abstract. In mud-and-thatch houses of Santiago del Estero Province, northwest Argentina, where no insecticides had been sprayed officially to control domestic infestations of the Chagas disease vector Triatoma infestans (Klug) (Hemiptera: Reduviidae), two knockdown (KD) insecticidal collection procedures were compared with the standard flush-out (FO) method for sampling T. infestans. Bugs were collected by FO using 0.2% tetramethrin in bedrooms of (1) 41 houses of Amama village employing 1 man-hour of capture effort per house, and (2) 19 houses of Trinidad and Mercedes villages employing 4 man-hours/house. From the same houses, 2-5 days after the manual FO collection, bugs were collected by KD indoor-spraying of deltamethrin 25mga.i./m² in Amama, or burning of one γ-HCH (=γ-BHC) fumigant tablet 3.1g of γ-isomer) per bedroom in Trinidad and Mercedes. The majority of infestations were detected by both methods, the proportion of positive houses being 81% at Amama and 95% at the other villages. Although the FO method was more sensitive, at least because it was applied first, the KD method detected infestations in 25% of houses where bugs were not found by FO. Bug densities estimated by FO or by subsequent KD in each house were significantly correlated: r = 0.795 for deltamethrin; r= 0.882 for y-HCH. Compared with FO collections of T.infestans large stages, i.e. adults plus fourth and fifth instar nymphs, the KD catch averaged 0.88x with deltamethrin and 0.57× with γ-HCH, regardless of the apparent population density of bugs per house. However, the KD method has practical advantages of speed and standardization.     

Acetate Oxidation by Bloodstream Forms of Trypanosoma cruzi*

Bloodstream forms of Trypanosoma cruzi had a substantial increase in respiration in the presence of acetate. Oxidation of acetate took place via the tricarboxylic acid cycle and involved an antimycin A-sensitive respiratory pathway. Oxygen uptake in the presence of acetate was as sensitive to antimycin A inhibition as was CO₂ production. There was a 6–7% residual O₂ uptake which was not inhibited by high antimycin concentrations. Human anti-T. cruzi sera had no effect on oxygen uptake.     

Host‐associated genetic divergence and taxonomy in the Rhinusa pilosa Gyllenhal species complex: an integrative approach

A combined taxonomic, morphological, molecular and biological study revealed that stem‐galling weevils from the genus Rhinusa associated with toadflaxes from the genus Linaria (Plantaginaceae) are composed of three different species: Rhinusa pilosa, Rhinusa brondelii and Rhinusa rara sp.n. The authentic field host plants are respectively, Linaria vulgaris, Linaria purpurea and Linaria genistifolia/ Linaria dalmatica. These weevil species can be distinguished from each other by a few subtle morphological characteristics, mainly in the shape of the rostrum and of the integument. An analysis of the mitochondrial [cytochrome oxidase subunit II gene (COII) and 16S ribosomal RNA gene (16S)] and nuclear (elongation factor‐1α, EF‐1α) sequence data revealed high genetic divergence among these species. Uncorrected pairwise distances on mtCOII gene were 14.3% between R. pilosa and R. brondelii, 15.7% between R. pilosa and R. rara, while R. brondelii and R. rara were approximately 11% divergent from each other. Divergences obtained on 16S and nuclear EF‐1α genes were congruent. However, substantial intraspecific mitochondrial divergence was recorded for all studied populations of R. pilosa s.s. showing two mtDNA lineages, with estimated COII and 16S divergences of 4% and 1.6%, respectively. Nuclear pseudogenes (Numts) and Wolbachia influence, although recorded within both lineages, were excluded as possible causatives of the mtDNA divergence, while EF‐1α indicated absence of lineage sorting. Species from the R. pilosa complex are estimated to have diverged from each other approximately 7.2 million years ago (mya; late Miocene), while R. brondelii and R. rara diverged from each other about 4.7 mya (early Pliocene). This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:EEDD6248‐01DB‐4B4A‐B79D‐C5606393E3AA .