Diel activity patterns and arrestment behaviour in host associations of green mirids (Creontiades dilutus)

Many plant bugs (Miridae) are generalist herbivores that feed on multiple host species. The reasons these bugs move across hosts and the behavioural mechanisms responsible for their retention at specific hosts remain elusive. Green mirids (Creontiades dilutus) are endemic to Australia. These insects are important pests of cotton (Gossypium hirsutum) and even in low numbers can cause substantial damage to crops. These bugs are also present in relatively much higher numbers on pigeon pea (Cajanus cajan) planted alongside cotton fields, and evidence shows they move across these crops in both directions. Observations of these highly mobile insects in the field are challenging, but indirect evidence suggests that they may be nocturnal. This study evaluated: (1) the diel (24 h) period in which C. dilutus adults were most active, (2) whether they respond to plant volatiles immediately prior to landing on host substrates, and (3) if their presence on a host is in response to attraction or arrestment cues. The results suggest that C. dilutus bugs are typically most active early in the evenings, after remaining motionless during the day (unless disturbed). Their movement (at night) was arrested by hosts prior to touching plant tissues. There was no evidence to suggest that these bugs are attracted by volatiles beyond 2 cm. These outcomes demonstrate that insect behaviours need to be investigated within their typical activity periods, and that arrestment cues possibly play a central role in the host finding process of generalist C. dilutus and probably, therefore, other mirid species.