Most of the basic features of an adult fly develop within the puparium in 48 hours.
Full development requires 3–21 days depending on temperature. The threshold for pupal development is about 11 °C (52 °F).
Typical times for pupal development at different temperatures are as follows:
| °C |
°F |
Days to adult emergence |
| 16 |
61 |
18– 21 |
| 18 |
64 |
12– 15 |
| 20 |
68 |
10– 11 |
| 25 |
77 |
7 – 9 |
| 30 |
86 |
4 – 5 |
| 35 |
95 |
3 – 4 |
Upon completion of adult development, the adult pushes off the anterior end of the puparium. A circular slit appears in segment six (fifth visible segment) of the puparium and the detached cap splits into two parts. This is done with the ptilinum, an inflated sac that protrudes from the frontal region of the head just dorsal to the base of the antennae of the adult fly (Figure 14).
Eversion of the ptilinum is by changes in blood pressure and contraction is by muscles. Once its head is free, the fly crawls out of the puparium. It crawls about while the wings unfold and the exoskeleton hardens and dries. When completely withdrawn, the ptilinum leaves only the crescent-shaped suture (frontal lunule) above the antennae.
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