Figure 1.

Experimental design. (a) Within generation priming experiment. Second instar larvae (8 days) were collected from the food and starved. Half were orally primed with virus solution of concentration equivalent to LD₁ and the other half were primed with control solution. When these larvae reached fourth instar (14 days) they were orally challenged with virus solution of concentration equivalent to LD₅₀. To determine the level of infection that resulted from prime inoculation some larvae primed with virus were challenged with control solution. This figure outlines the procedure for one experimental block. This study was carried out in six blocks. (b) Transgeneration priming experiment. Third instar (11days) F₁ generation larvae were removed from six containers established from the same large outbred insect stock, kept separately and starved. Larvae from three containers were primed with virus of concentration equivalent to LD₁ and larvae from the other three containers were primed with a control solution. These primed larvae were left to develop and make six F₂ generations. The small number of larvae that became infected following the virus prime treatment were removed immediately once they showed symptoms. Third instar (11 days) F₂ generation larvae from each container were then challenged with virus solution of concentration equivalent to LD₅₀. This figure outlines the procedure for one experimental replicate. This study was carried out in six blocks with three replicates of virus prime and three replicates of control prime per block.