“…However, the expression of clk and cyc is approximately phase coincident in the heads of the mosquitos A. aegypti , A. gambiae , and C. quinquefasciatus , peaking in the early morning, and in foragers such as the ant Solenopsis invicta , peaking in midday (Gentile et al., ; Ptitsyn et al., ; Ingram et al., ). Nevertheless, in most analyzed species thus far, only one of these genes is rhythmically transcribed, either clk in the heads of D. melanogaster and the house fly M. domestica , peaking during the night–day transition, or cyc , which peaks in the heads of the firebrat Thermobia domestica in the evening, in the brains of A. mellifera foragers in the late night, in the heads of A. pisum in the late night, and in the optic lobes of the cricket Gryllus bimaculatus at midnight (Rubin et al., ; Codd et al., ; Cortes et al., ; Kamae et al., ; Moriyama et al., ; Uryu et al., ). Based on these observations, some authors have proposed the following three patterns of clk and cyc expression: the Drosophila ‐like pattern with rhythmic clk only, the mammalian‐like pattern with rhythmic cyc (because in mammals the transcript abundance of the cyc homologue oscillates instead of clk ), and situations similar to that shown in D. pulex with simultaneous cycling of clk and cyc mRNAs (Tomioka and Matsumoto, ).…”