Dancing David
Penultimate Amazing
Okay, fair enough, again I feel I would have agreed more quickly if not right away. 'Sun angle' is an old term, but certainly has no bearing on deciduous trees, there degree days is the more important term.
There are some interesting stories about polarized light and possible uses of magnetism.
Now part of what I addressed before is that I was just saying that the genetic information is triggered and there is a response.
To my mind and perhaps incorrectly there are reasons in addition to genetics that the migratory butterflies live longer.
And so again (possibilities):
-mating and patrolling is turned off
This possibly effects the level of predation by birds and others.
Patrolling (not a technical term) is part of mating. Males cruises around nectars sources and between nectar sources. Females cruise around looking for larval food sources and returning to nectar sources. This makes the females in particular very vulnerable to predation, they land on potential sources and taste them by tapping with a foot. This landing in tasting in addition to the actual egg laying is a huge vulnerability.
Mating is in itself very stressful, again more so on the female. If you can find a large nectar sources in the magic month of August you will see what I mean, you will have a large number of males hanging out checking each other out. And when they sense a female they begin to chase her. She then engages in evasive action, which has some common characteristics, dart away, rise up, dart away. But then she has to avoid the nectar sources until the males settle down and then try to nectar.
The act of mating is a very vulnerable time for the male and female. The males bumps the female and narcs her out with hormones (if she does not succeed in getting away) and then he clasps her and flies for both of them.
Now I note that there is a pre migration phase (very short) where there is no mating pursuit behavior and just nectaring, sometimes you will see females laying and males chasing during this time. But generally the monarchs just nectar and rest.
-the impact of severe weather
And earlier I also mentioned thunderstorms, rainy weather in general, coupled with cooler temps is very hard on butterflies (especially the larvae). If we have a good soaking rain that lasts for days, there is a very high chance that it will damage adults, by getting them very wet, which makes them vulnerable to diseases.
But the more severe the weather, the more impact it has on the butterfly adults, one consequence of heavy rain is drowning. Birds caught on the ground often drown in a heavy downpour (or at least that is the story) and the same is very true of imagoes, they can be knocked off trees, and drowned or damaged while on the ground. Soil, wet soil is a great vector for disease.
They often do cute things like roost on the underside of a leaf or on the bark of a tree, and when the wind gets high enough this is not a very safe place to be, consequence drowning, disease and damage.
Then there are the wonders of hail bursts. I have seen all sorts of hail in summer thunderstorms, six inches of small hail, pea sized hail on up to gold ball hail are not uncommon. (I have seen some hail larger than gold ball, but that is rare here in Illinois). It pounds the crap out of plants, shredding leaves and knocking down plants, car dent are a real issue at times. This sort of hailstorm while localized is very damaging to butterflies.
So while there are likely genetic triggers involved in the life span of the migratory generation: these two things very highly could have some impact upon survival of the migratory generation.
If you are flying and nectaring, flying and roosting. You are less likely to suffer predation than when you’re are patrolling a local area and mating.
And while there is weather on the migratory pathways (especially the northern trip), there is not the effect where a hundred mile long (or states spanning) wave of severe weather rolls through an area and wipes out large number of adult butterflies. There are times in summer where these very large storm bands will come through repeatedly, covering a very large area repeatedly. High winds and heavy rains over a huge area over successive times.
So I assume that there is a level of storm damage that is not going to be there.
Now there are some strange things about the roosting populations that over winter. Some studies have shown that they are very much dominated by male butterflies (at least in the past).
They do spend a lot of time just roosting and maybe have a way to avoid freezing. They expend much less energy than during the mating period.
And they are still prone to predation by birds, one article says that two species of bird just gorge on the butterflies.
There are some interesting stories about polarized light and possible uses of magnetism.
Now part of what I addressed before is that I was just saying that the genetic information is triggered and there is a response.
To my mind and perhaps incorrectly there are reasons in addition to genetics that the migratory butterflies live longer.
And so again (possibilities):
-mating and patrolling is turned off
This possibly effects the level of predation by birds and others.
Patrolling (not a technical term) is part of mating. Males cruises around nectars sources and between nectar sources. Females cruise around looking for larval food sources and returning to nectar sources. This makes the females in particular very vulnerable to predation, they land on potential sources and taste them by tapping with a foot. This landing in tasting in addition to the actual egg laying is a huge vulnerability.
Mating is in itself very stressful, again more so on the female. If you can find a large nectar sources in the magic month of August you will see what I mean, you will have a large number of males hanging out checking each other out. And when they sense a female they begin to chase her. She then engages in evasive action, which has some common characteristics, dart away, rise up, dart away. But then she has to avoid the nectar sources until the males settle down and then try to nectar.
The act of mating is a very vulnerable time for the male and female. The males bumps the female and narcs her out with hormones (if she does not succeed in getting away) and then he clasps her and flies for both of them.
Now I note that there is a pre migration phase (very short) where there is no mating pursuit behavior and just nectaring, sometimes you will see females laying and males chasing during this time. But generally the monarchs just nectar and rest.
-the impact of severe weather
And earlier I also mentioned thunderstorms, rainy weather in general, coupled with cooler temps is very hard on butterflies (especially the larvae). If we have a good soaking rain that lasts for days, there is a very high chance that it will damage adults, by getting them very wet, which makes them vulnerable to diseases.
But the more severe the weather, the more impact it has on the butterfly adults, one consequence of heavy rain is drowning. Birds caught on the ground often drown in a heavy downpour (or at least that is the story) and the same is very true of imagoes, they can be knocked off trees, and drowned or damaged while on the ground. Soil, wet soil is a great vector for disease.
They often do cute things like roost on the underside of a leaf or on the bark of a tree, and when the wind gets high enough this is not a very safe place to be, consequence drowning, disease and damage.
Then there are the wonders of hail bursts. I have seen all sorts of hail in summer thunderstorms, six inches of small hail, pea sized hail on up to gold ball hail are not uncommon. (I have seen some hail larger than gold ball, but that is rare here in Illinois). It pounds the crap out of plants, shredding leaves and knocking down plants, car dent are a real issue at times. This sort of hailstorm while localized is very damaging to butterflies.
So while there are likely genetic triggers involved in the life span of the migratory generation: these two things very highly could have some impact upon survival of the migratory generation.
If you are flying and nectaring, flying and roosting. You are less likely to suffer predation than when you’re are patrolling a local area and mating.
And while there is weather on the migratory pathways (especially the northern trip), there is not the effect where a hundred mile long (or states spanning) wave of severe weather rolls through an area and wipes out large number of adult butterflies. There are times in summer where these very large storm bands will come through repeatedly, covering a very large area repeatedly. High winds and heavy rains over a huge area over successive times.
So I assume that there is a level of storm damage that is not going to be there.
Now there are some strange things about the roosting populations that over winter. Some studies have shown that they are very much dominated by male butterflies (at least in the past).
They do spend a lot of time just roosting and maybe have a way to avoid freezing. They expend much less energy than during the mating period.
And they are still prone to predation by birds, one article says that two species of bird just gorge on the butterflies.
