Wolbachia, belonging to Alphaproteobacteria, is ubiquitously found in arthropods and filarial nematodes, and is known to manipulate the reproduction of its hosts in various ways, such as feminization, male killing, induction of parthenogenesis or induction of cytoplasmic incompatibility. We found that the Wolbachia infection frequencies of the butterfly Colias erate poliographus were high (85.7–100%) in seven Japanese populations. Crossing experiments and rearing revealed that the Wolbachia strain exhibited strong cytoplasmic incompatibility and perfect vertical transmission in C. erate poliographus. Moreover, a comparison of the survival rates between infected and cured broods suggested that Wolbachia infection had beneficial effects on host fitness. Our findings suggested that the high infection frequencies in Japanese populations have been accomplished by these advantageous traits of the Wolbachia strain. Furthermore, the multilocus sequence typing (MLST) scheme revealed that the Wolbachia in C. erate poliographus is a novel strain (ST141), belonging to supergroup B.

The outcome and the evolution of host-symbiont associations depend on environmental constraints, but responses are difficult to predict since they arise from a complex interaction between the host, the parasite and the environment. The situation can be even more complex when multiple parasite genotypes, with potentially different responses to environmental changes, coexist within a single host. In this paper, we investigated the effect of the temperature (from 14 to 26 °C) during the host development on the density of 3 strains of the intracellular bacterium Wolbachia that coexist within the wasp Leptopilina heterotoma. In this species, Wolbachia induces cytoplasmic incompatibility, a sperm-egg incompatibility that allows it to spread and persist in host populations. Using real-time quantitative PCR we found that (i) Wolbachia density is temperature-specific and highest at 26 °C; (ii) the order of the abundance of the 3 Wolbachia strains does not vary with temperature changes; (iii) the response of bacterial density to temperature occurs within a single insect generation, during the egg-to-adult developmental period; (iv) in this species, temperature-related changes in Wolbachia density do not influence cytoplasmic incompatibility.

Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) is an indigenous, gregarious, larval endo/parasitoid which is widely distributed in Africa and attacks mid- to late instars of stemborers. There is renewed interest in using Co. sesamiae for biological control to reduce the problems caused by stemborers. However, Wolbachia sp., a bacterial symbiont of some populations of Co. sesamiae, poses some threat to the successful use of the parasitoid for stemborer control. This bacterium's common effect is cytoplasmic incompatibility between infected males and uninfected females. Polymerase chain reaction (PCR) tests were carried out on parasitoid samples collected from 5 locations in Kenya and 8 other countries in eastern Africa. Wolbachia presence was detected in Co. sesamiae populations from Coast and Machakos in Kenya, and from samples collected from 6 other eastern and southern African countries. No infection was detected from western Kenya, Uganda and Malawi. Cross mating among 3 infected populations (North Coast, South Coast and Machakos) and 2 uninfected populations (Kitale and Kuja) was done to establish which populations were reproductively compatible. Biological parameters, such as brood size and percent females were compared among the different crosses. One-way incompatibility, indicative of Wolbachia infection, was observed from the crosses between males of either Mombasa or Machakos arid females from Kitale. Selection of compatible Co. sesamiae populations is critical to successful augmentation biological control programmes.

Endosymbiotic bacteria of the genus Wolbachia infect a number of invertebrate species in which they induce various alterations in host reproduction, mainly cytoplasmic incompatibility (CI). In contrast to most other maternally transmitted parasites, manipulation of host reproduction makes the spread of Wolbachia possible even if they induce a physiological cost on their hosts. Current studies have shown that fitness consequences of Wolbachia infection could range from positive (mutualist) to negative (parasitic) but, in most cases, Wolbachia do not have strong deleterious effects on host fitness and the status of association remains unclear. Here, we show that in the Drosophila parasitoid wasp Leptopilina heterotoma, Wolbachia infection has a negative impact on several host fitness traits of both sexes. Fecundity, adult survival and locomotor performance are significantly reduced, whereas circadian rhythm, development time and offspring sex-ratio are not affected. Although the cost of bacterial infection can be overcome by effects on host reproduction i.e. cytoplasmic incompatibility, it could influence the spread of the bacterium at the early stages of the invasion process. Clearly, results underline the wide spectrum of phenotypic effects of Wolbachia infection and, to our knowledge, Wolbachia infection of L. heterotoma appears to be one of the most virulent that has ever been observed in insects.

The use of incompatible males (IM) of (A) mating type to suppress the Iraqi (B) strain of Ephestia cautella, when the release ratio was 80:1:1 (A males: B males: B females, respectively), brought about a highly successful protection of uncovered loose dates against infestation with (B) strain in a simulated date store. Surprisingly the protection effect of IMs lasted for 230 days which commercially covers almost the whole period of date storage.

Since strain A males are believed to compete poorly against wild strain B males, the competitiveness of F1 males was measured in order to determine if they might be promising candidates for subsequent trials of the control of E. cautella by the release of incompatible males.