Although H. charithonia is to some extent static, maintaining a home range, adults do move between territories. Butterflies with Mexican origins migrate north into Texas, following the retracting temperature gradient. Rainfall has no effect on migration patterns. Arrival dates and duration of stay depend on the distance traveled: the longer the distance traveled, the shorter the duration of stay.
Roosting to deter predators
Adults roost in groups of up to 60 individuals on a nightly basis, returning to the same roost every night. These roosts provide protection to adults, the large groups deterring predators and retaining warmth. Solitary individuals, or very small roosts, avoid exhibiting proper warning signals so as not to attract predators. Pre-roosting interactions, which consist of sitting near one another, chasing each other briefly while fluttering, or basking, occur between butterflies from separate roosts, indicating that the butterflies are aware of other roosts in their home range. Despite this, the zebra longwing chooses to form smaller aggregations. The optimal roost size for predator deterrence is five individuals; roost size is also influenced by resource availability and foraging. H. charithonia roosts to display collective aposematism, deterring predators by conspicuously advertising their unpalatable taste.
H. charithonia adults form communal roosts nightly. Communal roosting occurs when individuals aggregate at a particular site for more than a few hours. Roosting begins as early as three hours before sunset and usually ends within two hours after sunrise. Since roosting is at night, adults need to be able to see at low light levels to locate roost sites, either when looking for twigs, tendrils, and dry leaves to land on to start a roost, or when searching for conspecifics that are already roosting. Their eyes also help them to recognize color patterns in conspecifics. UV rhodopsins in the eye help them to distinguish between 3-OHK yellow pigments, or ultraviolet colors, and other yellow pigments, which to the human eye is indistinguishable. At shorter distances, the butterflies recognize conspecifics via chemical cues. These chemical cues include volatile and nonvolatile substances. The significance of this chemical communication remains largely unknown for Heliconius in general. However, in H. melpomene, (E)-?-ocimene was found to attract males and females in diurnal situations.
At eclosion, the ratio is highly female biased, but the rest of the year the sex ratio is overall male biased (68% males). This is because males typically stay near their natal sites to find a mate, while females move around to find oviposition or feeding sites on Passiflora plants. Because females are very mobile, males rarely mate with relatives, and inbreeding rates are very low.
No comments:
Post a Comment