This is an interesting question and one that I initially felt I would only be able to speculate on. But, thanks to my copy of the extraordinary book by E.O. Wilson and Holldobler - "The Ants" - I actually found some authoritative information. It may boil down to the fact that every species of animal has the "ideal" circumstances for their activity periods - foraging, nest building, etc. Those adapted to any particular habitat are going to do best at a certain range of temperatures and moisture conditions. Honeybees may not emerge for food gathering until temperatures reach a certain minimum and may halt their outside activity when the temperature reaches a certain maximum acceptable for them.
Likewise, ants react to temperature and humidity, and in particular the exposed workers outside of the nest. A colony in the soil can somewhat moderate their own living conditions by maintaining the temperature and humidity levels by clustering together or moving deeper in the soil. But, if the ideal conditions do not exist above soil level or within the first few inches of the surface the colony may forego swarming flights or workers may not emerge to forage. For ant species that have evolved in a desert environment, such as red harvester ants, the ideal humidity may be much lower than that of the Red Imported Fire Ant, which evolved in tropical rainforests. Ants evolved to live in the Upper Midwest or in Canada would prefer outside conditions to be at temperatures lower than ants native to Florida or Arizona, so a heat wave in Wisconsin could cause the ants to hole up in their colony until things return to the ideal state.
This can be said of many other insects as well - they are affected in some way by the weather. A particularly mild and dry winter is going to cause some insects to have population surges in the spring and others to not do as well. It often depends on what their food sources are, and a warm and rainy early spring could lead to more vegetation early in the year and thus more plant-feeding bugs to take advantage of this. This in turn might lead to more predatory insects that now have a greater food supply of the plant feeding bugs.
Ants may be at the top of the list when it comes to the affect of weather, as they all are social insects and thus work as a group for the benefit of the entire colony. When something outside the colony, such as the weather, is not conducive to their success they will withdraw and wait for things to return to normal.
Mr. Pest Control
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