Inherited bacteria that parasitically distort the pattern of sex allocation of their host, biasing allocation towards female progeny, are found in many arthropods. One such manipulation is male-killing, where male progeny of infected females die during embryogenesis. We here provide evidence for a male-killing bacterium in the coccinellid beetle, Adonia variegata. We then address 3 questions. First, is this male-killing bacterium one that is found in other hosts, or does it represent a new transition to male-killing within the eubacteria ? Using the sequence of the 16S rDNA of the bacterium, we found that the male-killing bacterium is a member of the Flavobacteria-Bacteroides group, most closely related to the male-killing bacterium in another lady bird beetle, Coleomegilla maculata. Secondly, is there any evidence that this bacterium affects female host physiology ? In a paired test under nutritional stress, we found no evidence for a physiological benefit to infection, and weak evidence of a physiological cost, in terms of reduced fecundity. Thirdly, is there any evidence of host involvement in the transmission of the bacterium to the germ line ? We found no evidence of host involvement. Rather, bacteria migrated to the ovariole independently of host cells. We conclude that thr bacterium is a parasite, and discuss how 2 different species of ladybird come to be infected with 1 lineage of bacterium, and why case studies of male-killing bacteria have generally found little evidence of any symbiont contribution to host physiological functioning.