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1962
Journal of the Lepidopterists' Society
249
ESPECIALLY FOR FIELD COLLECTORS
(Under the supervision of Fred T. Thorne, 1360 Merritt Dr., El Cajon, Calif., U.S.A.)
BUTTERFLY MIGRATIONS IN MARCH IN NORTHERN MEXICO
by Richard Heitzman
The freezing weather of 1961-62 spreading through southern Texas, killing the majority of the tropical growth in the area, resulted in very poor collecting for butterflies in the Rio Grande Valley. As a result of this my collecting partner William Howe and I decided to try for a few days collecting further south in Mexico. We entered Mexico through Matamoros on 21 March 1962 and headed south on the highway to CD. Victoria. About one hundred miles south of Matamoros a clogged fuel line caused a three hour delay which was used for collecting butterflies along the sides of the road. Butterflies were numerous, with many Phcebis and Kricogonia beating their way along the roadsides. We soon noticed that a small migration of Libytheana bachmanii larvata Strecker was in progress. All specimens observed were flying rapidly to the south from five to ten feet above the ground. Many specimens were caught and examined and all were found to be dull worn individuals. When released they would dash off to the south again. After we became aware that a migration was in progress, an attempt at counting was started, and in the next three hours, from 11 am until 2 pm, we counted 139 specimens. None were observed stopping at flowers or moist places along the road.
With the car operating again we continued south and about fifty miles north of CD. Victoria the first Danaus plexippus Linnaeus of the season was sighted. From this point on, scattered specimens were noted flying lazily to the northeast. UV light collecting during the evening surprised us by drawing in a big male D. plexippus. The next morning, 22 March, we left CD. Victoria heading south again for CD. Mante. We soon noticed a marked increase in the numbers of D. plexippus, and it was apparent that we were in the midst of a large migration. We started counting the ones that flew across in front of the car and found that 60 to 80 were passing for every mile traveled. These were only the ones flying directly in front of the car. The yellow flowers of the Palo Verde trees along the sides of the road were swarming with Monarchs. When we stopped the car and got out to look about, the species was everywhere, flying from a few feet above the ground far up into the sky until hardly
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Heitzman: Mexico
Vol.16: no.4
visible. All those flying were traveling at a leisurely rate to the northeast. These large numbers continued for the next 70 miles until we reached CD. Mante about 2:30 in the afternoon. The trees in the motel yard where we stayed were covered with resting Monachs. The owner told us they had appeared the day before, the same day that a heat wave jumped the temperatures about 30 degrees. For the next three days numbers of migrators were observed in the area but never approached the numbers of 22 March. When we returned to Brownsville, Texas, on 26 March, D. plexippus was common where not a one had been observed before. On 27 March we spent the day on Padre Island, about 30 miles east of Brownsville. Along the eastern shore many dead Monarchs were found washed up along the beach, apparently individuals that tried unsuccessfully to extend their flight across the Gulf.
3112 Harris Ave., Independence, Mo., U. S. A.
WILLIAM MARK DAVIDSON (1887-1961)
William M. Davidson, a member of the Lepidopterists' Society since 1948, died on 6 November 1961, at Orlando, Florida, where he had lived following his retirement in 1947.
He was born in Edinburgh, Scotland, 27 May 1887, and received his early education at Glen Almond School, Glasgow. In 1960 he emigrated to the United States, and he became a naturalized citizen in 1913. He was married in 1912 and had two children. He attended Stanford University and in 1910 received the A. B. degree. He was a Scientific Assistant in the U. S. Bureau of Entomology from 1911-20 and served as Assistant Entomologist and later Senior Entomologist in the U. S. Food Distributing Administration, 1920-46. His stations included Santa Clara and Sacramento, California, and Greenbelt, Maryland. He became a specialist in insecticides and in insects affecting citrus culture, especially the Orange Thrips and San Jose Scale.
Mr. Davidson published several short notes in the Lepidopterists News. His chief interest aside from Nearctic Lepidoptera was in bird banding. He was Secretary of the Florida Audubon Society from 1949 to 1961.
George W. Rawson, 603 Faulkner St., New Smyrna Beach, Fla., U. S. A.