Field-caught gravid femaleChironomus crassicaudatusMalloch in central Florida laid egg masses mostly in the morning at onset of photophase in the laboratory. Fifty-seven percent of these females laid a second egg mass in their adult life. Number of eggs averaged 1,338 and 245 per mass in the first and second mass, respectively. Average egg incubation period was 2 d, with initiation and cessation of egg hatch occurring at 1.5 and 5 d after oviposition, respectively. Relationship of body size and fecundity of femaleC. crassicaudatuswas studied by measuring wing length and examining number of eggs per mass and parity. Body size of nulliparous and of parous females had a significant linear relationship with dry body weight. Larger females had a significantly higher number of eggs per mass and percentage parity than small females.