Observations were made on 26 Brazilian fireflies species of the genera Cratomorphus, Aspisoma, Photinus, Macrolampis, Bicellonychia, Pyrogaster, Photuris, Amydetes, Lamprocera, and Lucidota occurring in the eastern region of Sao Paulo State. These species are adapted to mesophyl tropical forests, secondary growths, marshy areas, and open fields. Cratomorphini larvae were often arboreal and preyed on snails and slugs. Cratomorphus sp₂and Aspisoma sp₂inhabited marshy areas and their larvae were natural enemies of the aquatic snails Biomphalaria tenagophila Orbigny and Stenophisa columella Say. Photurinae species inhabited marshy areas and humid woody environments and their larvae were always found at ground level. The entire life-cycle of Bicellonychia sp₈lasted 11 mo. Most adult fireflies were active for less than 1 h during humid and hot spring evenings, from October to December, although many species were found active during the August–April period. Wave-synchronized bioluminescent signals were observed in Bicellonychia sp₈. Glow patterns in the green region of the spectrum were predominant among forest dwelling fireflies, whereas flash patterns in the yellow-green and yellow region were more commonly observed among open-field dwelling fireflies. This trend may be adaptation to luminescent signal optimization in different photic environments or for different signal functions, such as sexual attraction, defense and illumination.