6 E. B. Williamson 



With Mr. Carriker's data before us, we should have selected February 

 or March to May or June as the most favorable four months for our work, 

 but as other engagements prevented this we selected December-March as the 

 best months at our disposal. 



In selecting a time or season for zoological collecting in the tropics one 

 must of course take into consideration other factors than those of ram-fall. 

 The most essential of these factors are the group or groups of animals 

 especially sought, and the elevation at which collecting is contemplated. In 

 my case, experience in tropical collecting covers only the first six months 

 of the year and regions north of the equator. Without presuming to gen- 

 eralize from such limited experience, I believe that insect collecting generally 

 will prove profitable throughout the dry season in well watered lowlands up 

 to an elevation of five hundred and possibly in some cases one thousand 

 meters ; that high elevations tend during the dry season to become progres- 

 sively less productive as the elevation increases and as the season becomes 

 drier; that the most quiescent state of tropical animal life is attained as 

 the end of the dry season (April to June) is reached, and that at this tmie 

 many rarer lowland species which are to be found at no other season rqjpear 

 or attain their maturity ; and that the appearance of similar rarer species in 

 the higher altitudes awaits the showery rains (April to June) which re- 

 juvenate the fauna of both the high mountain valleys and the lowland 

 swamps with the sudden appearance of many species, often in great numbers. 



ITINERARY 



Jesse H. Williamson left Seattle, Washington, in October. I left my 

 home at Bluffton, Indiana, in November, and we met at Panama December 

 5. On December 6 and 7 Charles T. Tribolet and I collected at two small 

 streams in the Canal Zone. Several stream species were teneral ; of Perilestes 

 and Psaironcura rcmissa only tenerals were seen ; Coryphacschna adncxa was 

 pairing and ovipositing at a small back-water pool along the railroad track. 

 On December 7 it began raining before noon and rained hard the balance 

 of the day. December 8 was also rainy and no collecting was attempted. 

 The two days, December 6 and 7, mark the beginning and end of Mr. 

 Tribolet's career as a dragonfly hunter. While in the Canal Zone, v/e were 

 hospitably entertained at the home of Mr. and Mrs. Raymond Shady, former 

 lesidents of Wells County, Indiana. 



Enroute from Colon to Santa Marta, we collected about Puerto Co- 

 lombia, Colombia, on December 10 and 11. The country was very dry and 

 sandy, and back for three or four miles we found no running streams, only 

 small pools in creek beds. The so-called Arroyo Grande is a muddy, brack- 

 ish backwater at this season. Some of the coastal dragonflies which con- 

 gregate in great soaring flocks were abundant here. These flocks, usually 

 rather loosely organized, may consist of as many as six species, and hun- 

 dreds or thousands of individuals may be in view at one time. 



We landed at Santa Marta December 12. The surrounding hills are 

 dry and support a scanty vegetation at this season, cacti producing most of 



