sentence1: When a mosquito drinks the blood an infected person, the insect also swallows the malaria parasite, which then must incubate and multiply before migrating into the insect's saliva. The process can take weeks. And because mosquitoes are small-bodied and cold-blooded, outside temperatures make a big difference in how long it takes before they can transmit the disease. If it happens too slowly, the insects die before they can infect anyone. In general, the malaria parasite does better at warmer temperatures, which is why the disease occurs most often in tropical environments. But with mathematical models, Thomas has found that, even when conditions are warm, highly fluctuating temperatures over the course of a day slow down the rate of parasite incubation and larval development in the mosquito.
sentence2: Warm weather facilitates the spreading of malaria.