A COLLECTING TRIP TO COLOMBIA, SOUTH AME:rICA 



BY E. B. WILLIAMSON 



INTRODUCTION 



This trip to Colombia was made in the winter of 1916-19x7 for the 

 purpose of collecting dragonflies. The expenses were met by the Museum 

 of Zoology and by the members of the collecting party, Jesse H. and E. B. 

 Williamson, and the expedition will be known as the University of Michi- 

 gan-Williamson Expedition. Dragonfly collecting had been done in Central 

 America and in British Guiana by E. B. Williamson, and Colombia was se- 

 lected for the present trip as offering a readily accessible, intermediate and 

 relatively desirable region. . Enthusiastic accounts of Dr. Eigenmann and 

 Dr. Ruthven increased the writer's interest in the possibilities of Colombia as 

 a collecting ground for dragonflies. 



The time of year chosen for our trip was largely determined by in- 

 formation furnished us by Mr. M. A. Carriker, Jr., the well known bird 

 student and collector, whose long residence in Colombia enabled him to give 

 us accurately the data which we needed. This referred primarily to Santa 

 Marta, which we had selected as our landing place, and to the adjacent coun- 

 ti-y. At Santa Marta there are only two seasons, a dry season from Decem- 

 ber to March, inclusive, and a rainy season from April to November, in- 

 clusive. The first four months of the rainy season, April to July, inclusive, 

 are bright and showery. September, October and November are cloudy and 

 misty. The maximum drought is in Februai-y and March. The highest wa- 

 ter stage in rivers is reached in September to November, and the lowest in 

 March and April. Most birds nest in May, June and July, and most plants 

 flower in April, May and December. These conditions prevail moi-e or less 

 up the Magdalena River to Honda, but in the interior there are two rainy 

 and two dry seasons, the two dry seasons being December to Febiuary, in- 

 clusive, and June to August, inclusive. Other months are more or less rainy. 

 In some localities rains may occur at any time throughout the year but espe- 

 cially in October. These Colombian seasons do not correspond with the sea- 

 sons at Georgetown, British Guiana, where Mr. Rodway gave the writer 

 the following data: short rainy season, November 15-February 15 ; short dry 

 season, February 15-May 15; long rainy reason, May 15-August 15; long 

 dry season, August 15-November 15. From other sources it was- learned 

 that in British Guiana most birds nest in May and June ; showers may be- 

 gin in April; highwater stage is reached June 30-July 15; October and No- 

 vember are low water stages ; September is one of the most pleasant months, 

 and the short rainy season of November 15-February 15 is the most dis-^gree- 

 able time of the year, being misty or drizzly. 



