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observation. Since the outside colony and field populations were at 

 virtually the same latitude (Gainesville, Florida, 29°39.6' N; 

 D'Hanis, Texas, 29°20.0'N), they experienced almost identical 

 photoperiods. The photophase for October 16, 1983 was 11 hr 27 min 

 and 11 hr 28 min at D'Hanis and Gainesville, respectively. These 

 observations suggest that Lu . diabol ica is a long-day species, 

 depositing diapause eggs in response to shorter day length. The 

 percent diapause eggs increased from zero in early October to 100% in 

 December (Fig. 3-9). The critical day length, at which 50% of the 

 eggs were in diapause, occurred some time in November, which had a 

 mean photophase of 10 hr 41 min. Temperature may act indirectly in 

 long-day insects by modifying the degree of the diapause response or 

 by altering the position of the critical daylength (Saunders, 1976). 

 Therefore, some variation in onset of diapause may be expected from 

 year to year, depending on the mean fal 1 temperatures. Termination of 

 this winter diapause is probably temperature dependent and occurs in 

 the spring after a critical number of day degrees has accumulated 

 (Fig. 3-11). 



Quiescence in the larval stage has been reported by several 

 authors, with overwintering occurring in this stage. Most palearctic 

 species of sand flies are subject to a facultative diapause and pass 

 the winter as 4th stage larvae, low temperatures being the main, but 

 not the only factor which induces diapause (Adler and Theodor, 1957). 

 Addis (1945b), working in Texas with Lu. anthophora was unable to 

 obtain pupation of 4th instar larvae over a period of two months when 

 they were fed a mixture of dried rabbit feces and blood. When a few 

 drops of all known components of vitamin B complex were added to the 



