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Mixed Diglossini, Nov. 2, 1963, V. 
[[circled]] 49 [[/circled]]

[[left margin]] Carbo [[/left margin]] neath them. But, in any case, the change in the behavior of the [[male symbol]] immediately afterwards would seem to be conclusive in this connection.

[[left margin]] Carbo [[/left margin]] The fact that the [[male symbol]] stopped singing after copulation would suggest that the cop was successful. Does the fact that the A [[male symbol]] started to pounce with increased frequency after the presumed copulation attempt last week suggest that his copulation was unsuccessful???

[[left margin]] Carbo [[/left margin]] The behavior of the [[female symbol]] B Carbo this morning was rather peculiar in one respect. She kept returning to the inside of one bush, as if she were nest-building, but I never actually saw her carry n. m. Has she selected the site of the nest before beginning to build????

A few thoughts have occurred to me.

[[left margin]] General [[/left margin]] There must be a correlation between population density and the maintenance of strong and long-sustained pair bonds. It is only forms which have dense populations (e.g. C. lafresnayei and most ssp. of carbonaria s.l.) that can afford not to have such bonds. All the rarer forms (e.g Conirostrum spp., Cys, Carbos, and - probably - Pects) have to form close and long-sustained pairs. Otherwise individuals would have trouble finding sexual partners at the right times. 

[[left margin]] Brun Myst General [[/left margin]] There is some evidence that brunneiventris is a newcomer to Bolivia. (1). It does not form close pairs. In this respect, it differs from all other local forms of diglossini. (2). Bruns & Mysts are more similar to one another, in color pattern, than are Bruns and the Peruvian ssp. of lafresnayei (ie. unicincta, pectoralis, and albilinea). This evidence is valid only if selection pressure favors making the 2 species as different as possible (south of the special Ater-Laf area).