Adult dung beetles eat small particles of their food using soft mouthparts, but their larvae have biting jaws with which they chew material in their natal brood ball. It was assumed that microbes supplied by the parents help breakdown food material in the brood ball, which was thought to act as a fermentation chamber. It has been generally accepted that larval dung beetles gain access to nutrients in the dung via symbionts. Various dung treatments used here, including heat sterilisation and anti‐microbials, suggest that the maternal contribution to the brood ball is a pre‐digested meal for the newly hatched larva, and that microbes from the parents are not involved in larval feeding within this group of dung beetles. However, manipulation of the dung by the mother supplied the larva with smaller dung particles from the unsorted dung, and an additional ‘maternal gift’ secretion may provide partially digested dung, both of which affect survival of the larva. This overturns the largely untested dogma that larval dung beetles depend on microbial symbionts from the adults for feeding, but confirms that adult ‘conditioning’ of the dung is important for the larva in selecting out larger dung particles from the brood ball.

It has been well documented that baculovirus populations exhibit high levels of genetic variation. Due to the lack of sensitivity of the techniques currently used to study baculovirus genetic variation, relatively little is known about baculovirus genetic diversity at the individual insect level. Since denaturing gradient gel electrophoresis (DGGE) has key advantages over other methods used to study genetic variation in baculoviruses, DGGE assays were used to obtain a better understanding of the genetic variation within baculovirus populations in individual host insects. Helicoverpa armigera nucleopolyhedrovirus (HearNPV) was used as a model baculovirus system, and neonate H. armigera larvae were infected with one of two geographically distinct HearNPV isolates. DGGE assays for two lepidopteran-specific baculovirus genes, me53 and dbp1, detected many HearNPV genetic variants within individual host larvae, with up to 20 genetic variants detected in a 434-bp fragment of the dbp1 gene in a single neonate larva. High levels of HearNPV genetic diversity were detected in individual host larvae irrespective of the HearNPV isolate used to infect the larvae. This study sets a benchmark for HearNPV genetic variation in individual H. armigera larvae. The levels of HearNPV genetic diversity detected are higher than reported previously for a baculovirus population at the individual insect level.

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Environmental and infection variables may affect the genetic diversity of baculovirus populations. In this study, Helicoverpa armigera nucleopolyhedrovirus (HearNPV) was used as a model system for studying the effects of a key infection variable, inoculum dose, on the genetic diversity within nucleopolyhedrovirus populations. Diversity and equitability indices were calculated from DNA polymerase-specific denaturing gradient gel electrophoresis profiles obtained from individual H. armigera neonate larvae inoculated with either an LD 5 or LD 95 of HearNPV. Although the genetic diversity detected in larvae treated with an LD 95 was not statistically different from the diversity detected in the HearNPV inoculum samples, there was a statistically significant difference in the genetic diversity detected in the LD 5 -inoculated larvae compared with the genetic diversity detected in the HearNPV samples used for the inoculations. The study suggests that inoculum dose needs to be considered carefully in experiments that evaluate HearNPV genetic diversity or in studies where differences in genetic diversity may have phenotypic consequences.Baculoviruses are dsDNA viruses that are characterized by proteinaceous occlusion bodies (OBs) that enclose the virions (Funk et al., 1997;Theilmann & Blissard, 2008). The family Baculoviridae is divided into four genera (Alphabaculovirus, Betabaculovirus, Deltabaculovirus and Gammabaculovirus) based on phylogenetics, genome composition, host range, and morphological and pathological traits (Jehle et al., 2006). The alphabaculoviruses include the lepidopteran-specific nucleopolyhedroviruses (NPVs), which have virions that may contain a single nucleocapsid (SNPV) or multiple nucleocapsids (MNPV) (Theilmann & Blissard, 2008).Baculoviruses have been shown to have a high degree of genotypic variation between and within baculovirus isolates (Cory et al., 2005;Crook et al., 1985;Graham et al., 2004; Hitchman et al., 2007; Parnell et al., 2002;van Oers & Vlak, 2007). It has even been shown that baculovirus genetic variation can be detected within an individual host insect (Baillie & Bouwer, 2012b;Cory et al., 2005). Furthermore, Cory et al. (2005) showed that a number of the genetic variants isolated from a single host insect differed in phenotypic traits, including those for pathogenicity and kill time.The maintenance of genetic variation may be affected by host immune response specificity, tradeoffs between virus genotype fitness components, interactions of genotypes within the host, and differential selection of genotypes (Hitchman et al., 2007;Hodgson et al., 2001Hodgson et al., , 2002. Genetic heterogeneity must be important for the survival of baculoviruses as the less dominant (minority) viral variants are not lost from the virus population over time (Simó n et al., 2008). It has been shown that the minority genotypes affect the timing of mortality and the overall pathogenicity of the virus population (Simó n et al., 2005(Simó n et al., , 2008. The mixture of genotypes may consist of c...