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Volume 28, Number 2
175
We have found a report of aestivation in one species of Saturniidae, Rothschildia lebeaui ? aroma Schaus (Quezada 1967, Rev. Biol. Trop. 19: 211-240), whose pupa spends the six months of the dry season waiting for the first rains to fall. The dry season in this country starts in November and ends in April. The wet season starts in May and ends in October. Consequently the case we are reporting happened during part of the wet season and part of the dry. It is true that the weather was somewhat chaotic during 1972, there being a long spell of dry weather during July (20 days) and August (15 days), and then copious rain during November and the beginning of December.
Alberto Muyshondt, 101 Avenida Norte 322, Lomas Verdes, San Salvador, El Salvador.
AN INVASION OF EASTERN COLORADO BY VANESSA CARDUI (NYMPHALIDAE)
My notes for the Spring of 1973 show that cardui first came to my attention at Fountain Valley School (11 miles SE of Colorado Springs, Colo.) on 19 April. That day had started with near freezing temperatures and a light snow flurry. At noon I saw two cardui flutter over the lawn. A week or ten days of warmish weather followed with early morning temperatures as high as 44° F. Around 1430 on 28 April I was driving south from Denver on State Highway 83. About five miles north of Parker I met swarms of cardui drifting toward the northeast. I estimated about 100/150 passing directly in front of me each mile. This continued almost all of the way home, about 70 miles. There was a break going over the Platte-Arkansas Divide.
Examination of the insect, as flying at Fountain Valley, showed the specimens to be badly worn to tattered and the ground color to be quite pale. The concentration on the lawns may have reached 500 per acre. These butterflies were feeding at dandelion flowers and later apple blossoms. The numbers held reasonably steady until 11 May when another wave arrived. These specimens were considerably larger, and much fresher and darker in color. A careful estimate made around 1530 that afternoon placed the numbers on the lawns (30 acres) at about 1,000 per acre and on the prairie (2,000 acres sampled) about 150 per acre. These concentrations remained relatively constant until the weekend of 19-20 May and the two succeeding days when the weather was rainy and cold. By 23 May there were very few cardui around, just about the normal situation.
On 18 May driving south on 1-25 to New Mexico, the numbers of cardui flying across the highway were high enough to materially reduce the efficiency of the automobile's radiator. It was necessary to stop after about 100 miles to clean the radiator and scrape the squashed remains from the windshield. This situation continued through the 18th and 19th.
There are very few thistles in the vicinity of Fountain Valley School. It will interesting to see if we have an abnormally large crop of cardui in early summer. If we do, it will be important to discover the alternate foodplant here. The several large patches of thistie known to me along highway 83 in Douglas County will be watched with interest.
Postscript: Larvae used Helianthella and two species of Lupinus after the few thistles were stripped to the ground.
F. Martin Brown, Fountain Valley Rural Station, Colorado Springs, Colorado 80911.