Submitted to: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/1999
Publication Date: N/A
Interpretive Summary: Most economically important insects are migrants; therefore, it is important to understand the processes of insect migration and colonization to better combat pests. Much of the interpretation of the significance of insect pest migration has been based on laboratory and field studies of milkweed bugs, especially Oncopeltus fasciatus. Here we show for the first ttime that males of the large milkweed bug, and two related species, are responsible for producing pheromones which help guide colonizing females to new habitats. In addition, it was discovered that parasites of the bugs usurp the pheromones as cues to find bugs to parasitize. This information expands the knowledge of how insects find new habitats, including agricultural crops, and will enable pest control descisions to be more scientifically based.
Technical Abstract: Research on insect migration has justifiably emphasized females - the so-called "oogenesis-flight syndrome" - since it is the females that place eggs into new habitats. The large and small milkweed bugs, Oncopeltus fasciatus and Lygaeus kalmii, respectively, have featured prominently in studies of insect migration and sequestration of host plant toxins for chemical defense. Here we report that males of these species, and males o another well-studied lygaeine (Neacoryphus bicrucis), produce pheromones in the metathoracic scent glands which in Heteroptera are usually considered to serve only a defensive role, and that these pheromones are exploited by a tachnid parasitoid as a host-finding kairomone. The pheromones are mixtures of C6 and C8 saturated and unsaturated esters reminiscent of lepidopteran pheromones, and the key compound of the O. fasciatus pheromone has now been correctly identified as (E)-2,7-octadienyl acetate. It is proposed that the concept of the oogenesis-flight syndrome for these kinds of insects must be expanded to accommodate the role of males in the migration process. The hypothesis is presented that male-produced pheromones play a significant role in guiding the colonization process in vagile Heteroptera. In addition, data is presented suggesting that there is a trade-off between the amount of pheromone produced by males of a colonizing species and the host breadth of the species.