Saturniidae of Finland

Aglia tau male, courtesy of Mario Meier

This page is dedicated to Kimmo Keinänen of Helsinki, Finland, who has greatly assisted me with the "Saturniidae" information below. Only two Saturniidae species are known from Finland.

"Aglia tau, flies here to ca 63 degrees north, or should I say from the southern coast up some 250-300 kilometers. Males fly during daytime, in 2000 and 2001 from 15th May to 26th May, but in 2002 from 3rd of May to 20th May. There have been 15-20 observations annually 35 km north of Helsinki. Males can be netted during day; you can catch one running after it.

(The moth is also seen in Sipoo and Järvenpää.)

"Saturnia pavonia flies about ten days earlier, males during daytime, very fast . These cannot be caught on the wing! They are captured when they approach a calling female. Pavonia is somewhat rare, but is found even in the extreme north of Finland. It is most common from the southern coast 150 km north, but is even found here at 70 degrees north (northern most region of Finland)!

(This species is confirmed in Järvenpää and Tuusula.)

"Females of both species come to light, but not often. I've seen one of each females, once, during 2000-2002."

The climate in Finland is comparable to (though a bit cooler than) that of New England or the Canadian Maritimes.
Lying between the 60th and 70th North parallels, with its capital, Helsinki, at the 60th parallel, nights can be very long and cool, especially during the months of the midnight sun. No wonder the male Saturniidae fly during the day!
Aglia tau probably fly as far north as Pietarsaaari, and Saturnia pavonia as far north as Inan.
Finland's climate is greatly influenced by its geographical position. It has both a maritime and a continental climate, depending on the direction of air flow. The mean temperature in Finland is several degrees (as much as 10°C in winter) higher than that of other areas in these latitudes, e.g. Siberia and south Greenland. The temperature is raised by the Baltic Sea, inland waters and, above all, by air flows from the Atlantic, which are warmed by the Gulf Stream.

When westerly winds prevail, the weather is warm and clear in most of the country due to the 'föhn' phenomenon caused by the Keel range. Despite the moderating effect of the ocean, the Asian continental climate also extends to Finland at times, manifesting itself as severe cold in winter and extreme heat in summer.

Spring, with a mean daily temperature from 0°C to 10°C., begins in early April in Åland and the southwestern archipelago and later in April elsewhere, except for northernmost Lapland, where it does not begin until early May.

Cocoons kept in artificial cold storage will begin emerging in April-May if temperatures are not kept below zero.

Summer, with a mean daily temperature consistently above 10°C., usually begins in late May in southern Finland and lasts until mid-September.

The regions north of the Arctic Circle (approximately 66 degrees North latitude; northern 1/3 of Finland) are characterized by 'polar days', when the sun does not set at all. The northernmost parts of Finland have 73 such days every year. Even in southern Finland, the longest day (around Midsummer) is nearly 19 hours long.

The warmest day of the year comes about one month after aphelion, i.e. around July 20, in the whole of Finland. I expect this would be around the time that most of the Saturniidae larvae in southern Finland would be spinning cocoons. In the northern regions, the added heat is probably necessary to keep larvae going rapidly before autumn cool weather arrives.

It can get qite hot in Finland with the highest summer temperatures in the Finnish interior from 32°C to 35°C. The cooling effects of the sea usually keep summer temperatures below 30°C in coastal areas.

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