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 big culprit here isn't civil or nautical twilight, which I've already discussed in another blog entry. It's astronomical twilight, the time when the Sun is 12Â° to 18Â° below the horizon. In cities and bright suburbs, or at full Moon, astronomical twilight is a non-issue; the sky is as dark as it ever gets by the end of nautical twilight. But at otherwise dark locations, the sky is still too light for serious deep-sky astronomy.