Data on activity and social behavior of the Chilean degu, Octodon degus, were gathered by direct observation of animals, some of which had been marked for individual recognition. Data from autopsies and external inspection of trapped animals suggested that most reproduction occurs in September at the latitude of Santiago. Degus are diurnal and show morning and evening activity peaks. Social organization is based on group territories, at least during the period after emergence of the young. Mound building (collecting a pile of sticks, stones, and cow dung) was associated with territorial marking. Females of the same social group may rear their young in a common nest burrow. Octodon degus burrows are sometimes used by Abrocoma bennetti, a similar sized rodent, and on two occasions nest burrows were found to be shared by young and mothers of both species.Octodon degus is a common rodent in central Chile and one of the most economically important. In some areas it is an agricultural pest. Degus do considerable damage to cultivated tuna, the edible fruit of the prickly pear cactus; Ipinza et aZ. (1971) reported that degus are known to damage wheat fields, vineyards, and orchards. Pefaur et aZ. (1968) reviewed the parasitological literature and reported that O. degus can host three species of parasites known to infect man. In the United States, this hystricomorph is becoming widely used in medical laboratories (Woods and Boraker, 1975).Despite the importance and abundance of O. degus, information on its natural history is almost completely lacking. Woods and Boraker ( 1975) provided a complete review of the literature on the species. In this paper I report observations made on a natural population of O. degus. METHODSThis study was carried out at the experiment station of the School of Agronomy of the University of Chile at Rinconada de Maipu (70 0 50'W, 33°31'S) near Santiago. The vegetation was a mixture of grasses and shrubs and was greatly influenced by cattle grazing. The dominant woody plants were Acacia caven and Proustia cuneifolia. Olivares and Casto (1971) described secondary plant succession at this site and the influence of Octodon degus on the herbaceous strata. Climatic data were given in Fulk (1975).Reproductive data were gathered by autopsy of kill-trapped animals and by inspection of live-trapped animals.Activity was monitored by making frequent 15-minute observations during the daylight hours for one day each month for six consecutive months beginning in May 1973. The number of animals seen in a delineated area around an elevated observation blind was considered a measure of activity. Between observations, air temperature in the shade 5 centimeters above the ground, sunlight intensity, and relative humidity were recorded.Information on social behavior was gathered by observing a nearby colony of degus from a similar blind. Before the start of observations, animals were live trapped, examined for reproductive condition, weighed, marked for individual recognition by hair clipping, 495

Use of bifocals, instead of single-vision glasses, by children with near-point esophoria seemed to slow myopia progression to a slight degree.

Myopia progression rates were slower during the 6-month periods that included all of the summer vacation than would be expected assuming no seasonal effect. Ocular growth was also slower in the summer; but that trend, in most cases, was statistically significant only for changes in vitreous chamber depth and not for axial length.

Six eyelashes, three from the upper lid and three from the lower lid, were epilated from 256 subjects and examined for Demodex. D. folliculorum (Simon) was found in 16% of the subjects. Mites were more abundant in older persons and in persons with diabetes. Mites also were associated with a scarcity of lashes in the lower lid. Hierarchical log-linear analysis showed that the associations of greater mite abundance with diabetes and with madarosis were independent of age. The 43 persons from whose lid margins Staphylococcus aureus was cultured seemed to have been more likely to have two or more mites than those without S. aureus (11.6 versus 5.2%), although this difference fell short of statistical significance (P = 0.125).