Melissodes tristis Cockerell 1894

Melissodes (Eumelissodes) tristis Cockerell

This is a widely distributed polylectic species occurring in southwestern United States and Mexico. LaBerge (1961) has recorded 881 females visiting 131 plant species representing 93 plant genera, without specifying which were taking pollen. Among these, he reported 104 females from Larrea (which he incorrectly assigned to the Leguminosae), based upon 11 collections, as against 336 from 134 collections from Compositae, the preferred group of hosts for most species of Eumelissodes. He interprets collection data as indicating that the species has three generations a year in Texas, New Mexico, and Arizona, the first in the latter half of April and the first half of May, the second and largest in early to middle July, and the third in the first half of September. In southeastern Arizona there is usually some Larrea in bloom during these periods, at least in a year with the minimum necessary spring and summer rains.

This species was found in significant numbers at nearly all of our collecting sites in southeastern Arizona and New Mexico. The females collect large quantities of Larrea pollen and are regarded by us as polylectic regulars. In the San Simon Valley, females usually appeared at the flowers between 0600 and 0700, disappearing between 1600 and 1700. They were most active in the morning, with the peak of pollen collecting between 0800 and 0900. Males were present from 0900 until about 1300 but were rarely numerous. During the morning hours the females usually forage on the outer flowers in the upper half of the plant. As the day progresses, they are more commonly active inside the plant.

Males sleep gregariously on successive nights on the same or adjacent dry stems and flower heads, near but not touching one another, with head downward and antennae extended; nonnesting females sleep individually near the males and occasionally among them (Linsley, 1962a). In the San Simon Valley the most commonly observed sleeping substrate is dried stems of Heterotheca subaxillaris.