Natural living condition of sampled locusts. (A) Sample locations of the migratory locust. Tibetan population was located on Tibetan Plateau (TP) with average altitude over 4 km, and North China population on North China Plain (NP) with average altitude below 50 m. (B) Partial oxygen pressures (p O2) of sample locations. The formula for atmosphere pressure in terms of altitude was given in the CRC Handbook of Chemistry and Physics (1996 edition) and was modified to calculate p O2. The p O2 was calculated using the formula , where p O2 is pressure in kilopascals and Z is altitude in meters.