Cicadas are found in Connecticut, where they are a loud and noticeable part of the summer insect population. These large, winged insects are known for the distinct sounds the males produce to attract mates. The state is home to two different types of cicadas, each with a unique life cycle and emergence pattern.
Annual Versus Periodical Cicadas in the State
The two main groups of cicadas in Connecticut are distinguished by the length and synchronization of their life cycles. Annual cicadas, often called Dog-Day cicadas, belong to the genus Neotibicen and appear every summer, typically from mid-July through September. Although they have a multi-year life cycle (two to five years developing underground as nymphs), their non-synchronized emergence ensures a portion of the population matures and appears annually.
Periodical cicadas, belonging to the genus Magicicada, have a longer, synchronized life cycle, appearing only once every 13 or 17 years in massive numbers. This long, prime-numbered cycle is thought to be a strategy to avoid the buildup of specialized predators. When they emerge, these insects rise from the earth in unison to reproduce during their brief adult lives.
Which Specific Broods Emerge in Connecticut
Periodical cicadas are categorized into specific groups called “Broods,” identified by Roman numerals that emerge on a predictable cycle. Connecticut is home to one currently active 17-year brood: Brood II. Since its last major emergence occurred in 2013, the next anticipated appearance will be in 2030.
Brood II is the state’s most widespread periodical population, with historical records dating back to 1843. The state was also historically home to Brood XI, a 17-year group restricted to northeastern Connecticut. Brood XI has not been recorded since its last confirmed emergence in 1954 and is now considered extinct. The potential extinction of Brood XI is linked to its range being at the northern edge of the species’ climatic tolerance. The only reliable, extant periodical cicada population in the state remains the 17-year Brood II.
Predicting Local Emergence and Distribution
The timing of a periodical cicada emergence is tied to environmental conditions underground, not solely the calendar year. Nymphs begin to emerge from the soil when the temperature at a depth of 7 to 8 inches consistently reaches 64 degrees Fahrenheit. This temperature threshold causes the mass emergence to occur in late May or early June in Connecticut.
The distribution of the active Brood II cicadas is restricted to the central portion of Connecticut. These populations are often found near the state’s traprock or basalt ridges, with historical presence recorded in areas like Hamden. Annual cicadas, conversely, are widely distributed across the state and are the source of the droning sound heard throughout the summer months. Their appearance begins in mid-summer, after the periodical cicadas have completed their brief adult life cycle.