June 1997 Therevidae Collecting Expedition to Sierra San Pedro Martir, Baja California, Mexico

by Michael E. Irwin

The first week of June was hectic. I had only returned from a two-week expedition to Guatemala on the last day of May. On June 4, I flew out of Champaign, Illinois, to meet up with Ev and Marion Schlinger in Santa Ynez, California. We used the Schlinger’s 4X4 Jeep Grand Cherokee for the trip to Baja California. The vehicle was packed to the brim with malaise traps and other collecting and camping gear, and by noon on June 5, Ev and I were headed south. We spent the night in Brawley, California, and crossed the border into Mexico on June 6. Our first destination was a desolate cattle ranch at the eastern base of the Sierra San Pedro Martir just west of Santa Clara. After considerable searching, the outwash of Diablo Canyon was located and we positioned three malaise traps at water holes in that wash. As the sun set, we gingerly picked our way along nonexistent roads and through a huge watermelon patch to the sleepy town of San Felipe where we spent the night.

The next day was rather chaotic. We had made plans to cross the Baja California peninsula at a small place called Valle de la Trinidad. After several inquiries, we located the correct road across the peninsula. We drove along this dirt track for some distance before encountering a swarm of activity. Numerous, shiny, over-sized, souped-up 4X4’s were jammed together and nearly cut off the road. Upon working their way to the front of this metallic jumble, we were told that this was the weekend of the Baja 500 car race and that the sliver of a road we were hoping to traverse was part of the raceway. Our only option was to reversed our tracks and take a diagonal paved road to Ensenada. En route, we placed three malaise traps in unique and promising habitats. Because the Baja 500 crowd had invaded Ensenada in huge numbers, we were fortunate to locate a hotel with a vacant room.

It was on June 8 that we headed southward along the Pacific Ocean, cut eastward at San Telmo, and finally got to our primary destination, the Parque Nacional de Sierra San Pedro Martir, a massive mountain range that divides Baja California into an eastern sector (San Felipe side) and a western sector (for about 200 km south of Ensenada). The highest peak in the range is about 3,100 meters (10,200 feet). As we climbed upward, we placed malaise traps at strategic localities that reflected the transitional vegetation zones. The climb was gradual with several successive ranges, each rising higher than the last. The vegetation changed from sparse chaparral to dense ribbonwood cover to manzanita thickets to oak woodland to mixed pine and finally pure Jeffrey pine stands. We set up camp in a dry meadow at about 2,450 meters. It froze every night but reached around 24° C. each afternoon. Clouds began to accumulate in the afternoons but, fortunately, no rain fell during the four days we camped in that meadow.

June 9 was spent placing malaise traps at strategic waterholes at elevations above 2,300 m. This was a memorable day because we discovered thousands of therevids at one of the higher waterholes, most belonging to one species, Ozodiceromyia nanella. That evening, the expedition organizers, Dr. Ernesto Franco, Department of Crop and Soil Sciences, Michigan State University; Dr. Horacio de la Cueva, Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (CICESE); and Dr. James Berry, state ecologist, Department of Parks and Recreation, Sacramento, CA, greeted us after returning from a two-day hike. They brought good news, that the collecting and export permits for therevids had been granted and had arrived from Mexico City.

The morning of June 10 was spent with Jim, Ernesto, and Heracio. They showed us magnificent vistas from the observatory, views of rugged country that stretched eastward across the Gulf of California and into Sonora and westward to the Pacific Ocean and beyond. In the afternoon, Ernesto and Horacio broke camp and headed to Ensenada. Meanwhile, we checked the malaise traps each day and curated the material to the level possible in the field.

On June 11, we broke camp, and Ev and I began to pull down the malaise traps while Jim drove to Ensenada. It was late in the afternoon when we left the national park and, fortunately, we were able to overnight at the Melin Guest Ranch, half way down the mountain towards San Telmo. A warm shower was very welcomed that evening.

June 12 was a travel day. We took the dirt track from Colonet to Valle de Trinidad, picked up the malaise trap we had placed there several days earlier, went to Santa Clara and the Canyon del Diablo, removed the malaise traps that were left in the wash there, then headed toward Ensenada, gathering en route the two traps that were placed along that road a week earlier. It was dark when we arrived.

The morning of June 13 was spent curating much of the malaise trap material gathered during the previous day’s travel. After lunch, we headed towards Tecate, crossed the border, and spent the night near Oceanside, California. The next morning we continued north to Santa Ynez. The trip lasted nine days. During that time, 17 different sites were sampled (see table below).

This expedition resulted in a number of species not known to occur in Baja California. Some material was collected dry and was pinned while some was collected in 95% ethanol for molecular studies. Fourteen therevid species were collected at those sites. They are presented in a table below, along with the vegetation zones and approximate elevation of the collections. Note that the various species seem to partition the environment, some occupying wider niches than others. This material will play a critical role in determining the distribution, ecological and evolutionary relationships among the lineages within this family.

The expedition received financial assistance from the Schlinger Foundation and the National Science Foundation’s Partnership for Enhancing Expertise in Taxonomy (PEET) program. It also was aided by the Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (CICESE), Baja California, Mexico, and its scientists, Drs. Horacio de la Cueva and Ernesto Franco. Thanks is also given to the Instituto Nacional de Ecologia, Direccion General de Vida Silvestre, Secretaria de Medio Ambiente, Recursos Naturales y Pesca of Mexico City for providing a permit to collect and study Therevidae in Baja California. Our special thanks go to Jim Berry who first suggested that we accompany him and the Mexican team to the Sierra de San Pedro Martir.