Eggs are off-white, and laid in clusters of 25-500.

One-day-old larvae are only about 2 mm in length, and almost transparent.

By the time the maggots are 3 or 4 days old, they have grown to about 1 cm (1/2 inch) long.

Note & disclaimer: These are generalizations only. Maggot sizes and ages are very dependent upon species of fly, local temperature, food source, and other environmental factors. The actual size and age of your maggots may be different.

The eggs and maggots seen here on a sterile petri dish (TSA-blood agar) are Phaenicia sericata.




 

Time of Death using maggot life cycle of the species Caliphora Vomitoria, the common blow fly

The blow fly has a superb sense of smell. It will discover the body within hours after death as the blood begins to breakdown within the body. 

Egg:  The eggs of the blowfly are very small and cannot be seen until two days have passed after being deposited on the corpse. 

mm scale

 Larvae:
The blowfly has three instars (stages of development) of larvae. The first instar is approximately 5 mm long after 1.8 days, the second instar is approximately 10 mm long after 2.5 days, the third instar is approximately 17 mm long after 4-5 days. Identifying the right instar is the easiest part, and is done relatively easy based on size of larvae, the size of the larva's mouth parts and morphology of the posterior spiracles the dot on the posterior end used for breathing. The time it takes to reach the different instars depends very much on microclimate, i.e. temperature and humidity

 Prepupae:
At the end of the third instar the larva becomes restless and starts to move away from the body. The crop (a neck part for temporary food storage) will gradually be emptied for blood, and the fat body will gradually obscure the internal features of the larvae. We say that the larva has become a prepupa. The prepupa is about 12 mm long, and is seen 8-12 days after oviposition.

Pupa:

The prepupa gradually becomes a pupa, which darkens with age and is seen as a hardened exterior as seen 18-24 days after oviposition. The metamorphosis into a fly will occur within the pupa.  The presence of empty pupa should therefore tell the forensic entomologist that the person in question has been dead in more than approximately 20 days.