Jigger (sand flea) infested foot. Tunga penetrans (chigoe flea or jigger) is a parasitic insect found in most tropical and sub-tropical climates. It is native to Central and South America, and has been inadvertently introduced by humans to sub-Saharan Africa. Synonyms for Tunga penetrans include Sarcopsylla penetrans, Pulex penetrates, and many others. In its parasitic phase it has significant impact on its host, which include humans and certain other mammalian species. A parasitical infestation of T. penetrans is called tungiasis.
According to data provided by the U.S. Navy Oceanography Portal (http://www.usno.navy.mil/USNO/as...), astronomical twilight lasts much longer (nearly 2 hours) during the summer compared to the winter months (only about 30-40 minutes).
The amount of visible light on the longest day of the year in the Northern Hemisphere. Day length refers to the period from sunrise to sunset. Civil twilight refers to the time before sunrise and after sunset when the sun is 6Âº or less below the horizon.