This sentence is saying that the higher number of insects you see during the growing season and the lower numbers seen throughout the rest of the year is because of the relationships between insects and temperature, where warmer temperatures result in greater insect populations. This pattern, fewer insects during colder months and more insects during warmer months, is called diapause and means that insects, and also some other animals, go into a dormancy until environmental conditions are more favorable for survival.

An increase in temperature of 2-4 degrees C could significantly reduce corn yields and other vegetables, making it even harder for people to get the necessary nutrients they need.

Read more at Inside Climate News: https://insideclimatenews.org/news/11062018/climate-change-research-food-security-agriculture-impacts-corn-vegetables-crop-prices

The growing season is the time of year when crops are grown because the temperature and rainfall during that time are most ideal for plant growth. The growing season will vary depending on where you are in the world.

metabolic rate is the amount of energy an organism uses up in a span of time. An organism with a higher metabolic rate will use up more energy than an organism with a low metabolic rate. Metabolic rate may change over time as well. This paper discusses how insects have greater metabolic needs in warmer temperatures and so they need to eat more to sustain their greater energy needs.

This equation is basically saying that the changes in crop losses due to pests can be determined by adding up the change in insect metabolism and the change in where the insects are located. If the metabolic needs of insects increases or the area that they live in increases, then crop losses will also go up.