It is at least 221 years before the cycle twice is met and evidence of hybridization is found

, published this week in The Journal of Communication-Biology
reported genetic evidence of 13-year and 17-year interbreeding. The discovery was surprising because 13 and 17 years were close relatives, but rarely met.1
left: A female 17-year-old magicada cassini lays eggs in a branch (Chris Simon); right: two 17-year-old magicic cassisani mating (Satoshi Kakishima).
spent most of their lives underground, and the larvae survive by sucking the juice of the roots of the tree. After living underground for 13 or 17 years, the same species of dragonflies broke through at the same time and became adult insects. The rest of their lives - less than a month - are dominated by reproduction. There are seven species of periodic slugs, divided into three groups, each containing a 17-year species and one or two 13-year species. With a few exceptions, 13 and 17 years occur at the same time every 221 years, and their geographical distribution does not significantly re-occur.species and
groupings of the 2nd cycle.
and colleagues at Kyoto University in , Japan, sequenced RNA from seven periodic species to gain a deeper understanding of their relationship. Surprisingly, the authors found evidence that in each group, 17 years of interbreeding occurred with their closest relatives of 13 years. Despite hybridization, these slugs have maintained their respective life cycles for up to 200,000 years. However, the authors cannot give a precise genetic explanation for this parallel heterogeneous evolution. In order to better understand how periodic tyring maintains different life cycles during evolution, further genome-wide sequencing of them is needed in the future. (Source: Science.com) 3
: Two 17-year-old magicada septendecim resting on a branch (Teiji Sota);