(a to f) Parasite number (a and b), and percent (c and d) and number (e and f) of metacyclics in Leishmania infantum-infected Lutzomyia longipalpis (a, c and r) or L. major-infected Phlebotomus papatasi (b, d and f) sand flies. (g to j), Haptomonads parasite sphere (HPS) in Lu. longipalpis. (g and h) HPS image in E1 (g) or E2 (h) sand flies. Bar, 50 μm. (i) HPS diameter. (j) In situ SEM of HPS. Blue, Haptomonads. Bar, 25 μm. E1, sand flies engorged on an infected blood meal (BM). E2, infected sand flies engorged on a subsequent uninfected BM. Red arrow, subsequent BM. Bar, Median. Cumulative data shown from four (a, c and e) or two (b, d, f and i) independent experiments; (a to f) n for each condition is specified in Supplementary Table 2. (g and h) images are representative of two independent experiments. P<0.05, ***P≤0.001, ****P≤0.0001 determined by Mann-Whitney’s U-test for parasite number and by N1-Chi-squared test for percent metacyclics.