It is easy for humans to minimize the design that is needed for life to exist on Earth. How do you feed massive numbers of birds, especially in the spring when winter has taken away most of their food sources, and their food needs are maximized as they lay eggs and feed baby birds? In the past scientists have shrugged their shoulders and imagined that there are food sources we don’t recognize that fill this gap until the summer season generates sufficient seeds and insects to sustain the growing populations. Similar problems exist for many other animals like bats that depend on insects for their nutritional needs.
In the April 2017 issue of Scientific American (page 84), there is an interesting report about previously unknown migrations of insects. We have known about monarch butterflies for some time, but this study by British researchers shows that migrations of insects are massive. Over southern Britain alone there are 3.3 trillion insects migrating. That is an average of 3200 tons of bugs moving through the skies over Britain every year. The study also reports that similar patterns have been observed in Texas, India, and China.
The complexity of this migration is astounding. Insects don’t live long enough for one bug to complete the migration. Researchers found that in some cases six generations were involved to complete a migration. The insects do not just get randomly blown about. They travel in a well-programmed pattern taking advantage of wind direction and speed. The elevation at which they fly to get the strongest support for their journey is carefully chosen. For a number of reasons, spring migrations are different from fall migrations.
Over the years we have presented data on some amazing migrations. We have had several discussions about the Arctic tern and how it makes its incredible 12,000-mile journey. Research has shown that the Arctic tern uses multiple cues including magnetism, sight, smell, and even sound. We have also talked about whales, salmon, and sea turtles and the way they benefit multiple ecosystems by their migrations. Now we have a new migration that has just been discovered and is equivalent to 20,000 flying reindeer.
The animals making this migration are insects. According to the study, 2-5 million of them fly over the United Kingdom each year. The study is reported in the December 23, 2016, issue of Science by a team headed by Jason Chapman. Tracking these arthropods involves the use of special radar designed to detect insects. The team estimates that the total biomass of these arthropods is 3200 tons which is 7.7 times more than the biomass of the songbirds in the same area. These are tiny creatures with some of them weighing less than 10 milligrams.
Chapman notes that these arthropods are not just accidentally caught up in the wind. Some of them climb to the top of a plant to launch their flight. Some stand on tiptoe and put out silk until the wind catches them and carries them away. The animals only launch when the wind is to the north from May to June, and in August and September, they launch when the wind blows to the south. Chapman concludes “these arthropods must have some kind of built-in compass plus a preferred direction and the genetics that change that preference as they or their offspring make the return migration.“