Reference : Hisn al-Muslim 97

أَعـوذُ بِكَلِمـاتِ اللّهِ التّـامّـاتِ مِنْ شَـرِّ ما خَلَـق
(ثلاث مرات إِذا أمسى)
A`ūdhu bikalimāti-llāhit-tāmmāti min sharri mā khalaq.

I seek refuge in the Perfect Words of Allah from the evil of what He has created. 
(Recite three times in Arabic in the evening.)

Reference:
Whoever recites this three times in the evening will be protected from 
insect stings, Ahmad 2/ 290, An-Nasa'i, 'Amalul-Yawm wal-Laylah no. 590, 
At-Tirmidhi 3/187, Ibn As-Sunni no. 68. According to Al-Albani, Ibn Majah's 
(2/266) chain of transmission is sound (Sahih), and following Ibn Baz 45, 
At-Tirmidhi's report is good (Hasan).

Chapter: In the morning and evening