ANNUAL PATTERNS OF AERIAL INSECT DENSITIES AT ALTITUDES FROM 500 TO 2400 METERS IN EAST-CENTRAL TEXAS INDICATED BY CONTINUOUSLY-OPERATING VERTICALLY-ORIENTED RADAR

Aerial insect densities were monitored continuously with an automated, vertically-oriented x-band radar system in the Brazos River Valley ar ea of Burleson County near College Station, TX during most of 1990 and 1991. The-primary emphasis of the research was the study of long-dist ance movement and flight behavior of noctuids which are important pest s of several agricultural crops. The sensitivity of the radar system w as such that noctuid-sized insects could be detected at a maximum alti tude of about 2450 m. Aerial densities of flying insects were determin ed by automatic counting of radar-detected targets in 64 discrete rang e intervals spanning the altitude range from ground level to 2432 m. I nsect densities were typically highest near ground level, they decreas ed nonlinearly with increasing altitude, and they were considerably re duced at altitudes above 800 m. There were apparent periodicities in t he aerial densities during both years which were probably caused by in teractions of the flight behaviors of several insect species, insect r eproduction cycles, and the effects of seasonal weather patterns. The data indicated that continuously-operating vertically-oriented radar s ystems can provide information useful to the understanding of the spat ial and temporal character of insect movement.