J Forensic Sci, 2010

doi: 10.1111/j.1556-4029.2010.01485.x
Available online at: interscience.wiley.com

CASE REPORT
PATHOLOGY BIOLOGY

Kumara Thevan,1 B.Sc.; Abu Hassan Ahmad,1 Ph.D.; Che Salmah Md. Rawi,1 Ph.D.;
and Bhupinder Singh,2 M.B.B.S.

Growth of Chrysomya megacephala

(Fabricius) Maggots in a Morgue Cooler*

ABSTRACT: In estimating the postmortem interval (PMI) using maggots obtained during autopsy, the forensic entomologist makes decisions
regarding the effects of low-temperature storage of the body on the insects. In this case report, a corpse was found in an abandoned house in the residential area of Bukit Mertajam, Penang, Malaysia. The maggots were found to be alive inside the mouth of the deceased although the corpse had
been in the morgue cooler for 12 days. The maggots were reared and identified as Chrysomya megacephala (Fabricius). The emerged adult flies were
kept as a stock colony, and the duration of development under the indoor fluctuating temperature regime was studied. The total duration of developmental process of this species was 9.5 0.5 days, and the PMI estimated was 3.2 0.6 days. This case report demonstrates the survival of
Ch. megacephala maggots for 12 days and their growth inside the morgue cooler.
KEYWORDS: forensic science, forensic entomology, Calliphoridae, postmortem interval, maggot mass, Malaysia
The growth and development of calliphorid (Diptera: Calliphoridae) larvae is of great interest to forensic science, especially for
estimation of a postmortem interval (PMI) (1). To obtain an estimate of the minimum PMI, one requires accurate identification of
the species recovered from the case, data on the temperature regime
prior to the taking of the samples, and relevant information on the
duration of development of the species at various temperatures (2).
Furthermore, the developmental rate of calliphorid larvae is influenced by the temperature of their immediate environment (1). There
are two main physiological responses to low temperatures: diapause
and quiescence (3,4). Diapause is a delay in development evolved
in response to regularly recurring periods of adverse environmental
conditions (3), whereas quiescence mainly stops development for a
short time and acts like an anesthetic. Quiescence is induced by the
immediate effect of temperatures ranging from 0 to 10C and
involves a deceleration of insect metabolic activity (4). However,
when a maggot mass is formed, the maggot mass temperature
may be sufficient to allow continued development and is essential
in allowing development (5). The objectives of this case study were
to highlight (i) the importance of the case history in PMI estimation
and (ii) the growth of blowfly maggots stored in a morgue cooler.
Case Report
On July 25, 2007, an unknown male corpse was found in an
empty house in the residential area of Bukit Mertajam, Penang,

1
School of Biological Sciences, Universiti Sains Malaysia, 11800 Penang,
Malaysia.
2
Institute of Forensic Medicine (Northern Region), Penang Hospital,
10990 Residensi Road, Penang, Malaysia.
*Funding provided by Universiti Sains Malaysia (USM) RU research
grant 1001 PBiology 815009.
Received 22 April 2009; and in revised form 6 Aug. 2009; accepted 13
Sept. 2009.

 2010 American Academy of Forensic Sciences

Malaysia (5 21N, 100 28E). The corpse was in active decay
stage and fully clothed. The autopsy was performed on the same
day the corpse was found, and no entomological specimens were
collected. After 5 days of the corpse being kept in the morgue
cooler, we were informed that maggots had infested the corpse.
The entomological specimens were collected on July 30, 2007, at
12.30 pm. Specimens taken were nonhairy maggots, which were
collected from the mouth (alive) and on the legs (dead). On
attempting rearing, the maggots failed to survive. Pending police
investigations, the corpse was still kept in the mortuary. On August
6, 2007, at 11.30 am, the second sampling was carried out. The
samples were one newly emerged adult (wings not developed), and
nonhairy pupae were found outside the morgue cooler (14 pupae).
Then, 34 nonhairy live maggots were taken from the mouth
(Fig. 1). There were no live maggots found inside the morgue
cooler beside the one in the mouth of the deceased. On rearing,
these live maggots survived and were identified as Ch. megacephala (Fabricius) using taxonomic keys provided by Greenberg &
Kunich (6). The temperature of the morgue cooler was at 4 3C,
and the temperature of the maggot mass inside the mouth was
12C. Unfortunately, the temperature of the scene of death was not
available.
In Malaysia, there is a lack of any published data regarding the
development time of Ch. megacephala under indoor fluctuating
temperature of Malaysian tropical climate. For the purpose of this
study, the emerged adults were maintained as a colony, and the
immature life cycle of this species was studied at room temperature
to simulate the scene of death. In this experiment, beef meat was
used as the rearing medium, and nine replicates were made. The
eggs were collected from the colony and were transferred into the
rearing containers [11.5 (h) 10.0 (w) 10.0 (L) cm] with 2.5 m
thick soil inside it. The maggots were fed with fresh beef meat
ad libitum. The developmental data, temperatures, and relative
humidity of the rearing were recorded from the time the eggs were
collected until the emergence. From each replicate, an average of
1

JOURNAL OF FORENSIC SCIENCES

FIG. 1The live maggot mass of Chrysomya megacephala (arrow) forming froths in the mouth of the corpse (photo taken during the first
sampling).

five maggots was randomly collected, every morning and evening

until the maggots reached the pupal stage. These maggots were
warm-water killed (52 10C) and preserved in Kahles solution.
The instar stages of the preserved maggots were recorded by determining the number of posterior spiracles slits under the stereomicroscope, and the lengths of the maggots were measured. For the
first and second instar, a slide of the posterior spiracles was prepared and observed under the light microscope. After the rearings
were completed, the developmental times (days) were calculated as
shown in Table 1, and the graph of larval length against developmental time (hours) was constructed (Fig. 2).
Results and Discussions
The average length of the dead Ch. megacephala (Fabricius)
maggots found on the legs during the first specimen collection was
13 mm (third instar). The recently emerged adult found outside the
body freezer failed to develop its wings and died. The 14 pupae

collected from outside the morgue cooler emerged on August 8,

2007, between 10 am and 4 pm. The live larvae that were collected
from the mouth of the deceased on first sample collection averaged
10 mm in length (third instar), and on the second sampling, the
length of the maggots was 13.5 mm (third instar). The reared live
larvae that were collected on second sampling turned into pupae on
August 8, 2007, at 4 pm and emerged on August 11, 2007, at
5 pm. The developmental time of the maggots from the time of
second sample collection until the pupal stage was 52.5 h. The
pupation period was 73 h (3 days). The mean temperature of the
rearing room was 29.5 1C, and the relative humidity was 61
79%.
Ch. megacephala also known as the Oriental latrines fly, is a
species of medical importance (7) and has been identified playing
an important role in forensic cases (8). This species, formerly Australasian and Pacific in distribution, is now widespread in Africa
and the Americas (9). In Malaysia, Ch. megacephala is now the
predominant species infesting human corpses (10). In this case
report, during the sampling periods, the live maggots were observed
to form froths above the maggot mass in the mouth (Fig. 1). When
the corpse was taken out from the morgue cooler, the maggots
went deep into the throat, and we managed to extract 34 maggots
only. The maggots grew 3.5 mm in length between the first and
second sample collection period (6 days). Under sub-optimal conditions, blowfly larvae can delay pupariation (9). In this case study,
the maggots of Ch. megacephala were found alive, infesting the
corpse placed in the morgue cooler for a total of 12 days in darkness (except during the sampling period), inside the mouth of the
deceased at the ambient temperature of 4 3C. A potential error
of 8.612.8% in PMI estimation was reported, if the assumption
that no insect development takes place during the preautopsy refrigeration is made (11); while others found low temperature (4C)
because of refrigeration affects the normal development of blowflies (12). This probably explains the shortened pupal period from
normal 3.9 days (Table 1) to 3.0 days (case specimens). In this
case study, the PMI was estimated by comparing their length with
the graph constructed in Fig. 2 because of several reasons: (i) the
most accurate estimation would be using the size of the oldest dead

TABLE 1The accumulated developmental time (days) of Chrysomya megacephala at the indoor rearing temperature of 29 2C and relative humidity of
5975%.
Immature Stages
Accumulated developmental time (days)

Eggs First Instar

Second Instar

Third Instar

Post Feeding

Pupa

Emergence

0.8 0.2

1.6 0.0

3.3 1.3

4.5 0.4

5.1 0.5

9.0 0.5

FIG. 2The larval length against developmental time (hours) of Chrysomya megacephala (nine replicates) at 29 2C.

THEVAN ET AL. GROWTH OF CHRYSOMYA MEGACEPHALA

maggots collected in the first sampling because there was no

degree-day reference data of this species at 12C available; (ii) we
did not know the exact temperature experienced by the maggots
throughout the 12-day period for the degree-days method to be
used, and there is evidence that maggots can thermoregulate their
temperature when maggot mass formed (13,14); (iii) the corpse
was found indoors and temperature data from nearby weather data
cannot be used while the temperature data of the scene of death
was not recorded; (iv) the use of larval length to determine PMI
was acceptable if both the scene of death and reference data were
at the almost similar environment (indoors) where the temperature
fluctuates little (15). The PMI was estimated between 64 h
(2.6 days) and 94 h (3.9 days) based on the length of the dead
maggots collected in the first sampling. If the PMI estimation on
the case was carried out using the length of live Ch. megacephala
maggots collected from the second sample (13.5 mm), the PMI
estimated would be still within the range estimated earlier; however, in reality the maggots were actually more than 12 days old.
Thus, the potential for blowfly larvae to undergo significant development while being stored in the morgue is a possibility that forensic entomologists should consider during an investigation involving
samples collected from autopsy (11). It was suggested that if the
time of death may be of interest in cases with insects colonization
of human corpses, preferably a person with experience in the field
of forensic entomology should be present at the crime scene or at
least during the autopsy (16,17). However, this is not a standard
practice in Malaysia, and without the knowledge of the case history
and the thermal history of the maggots, the forensic entomologist
must be cautious in estimating the PMI.
Acknowledgments
We thank Mr. Chan Kok Cheng, Mr. Mahashim Mahamud,
and Mr. Abdullah Shaari for their help during the period of
sample collections. Lastly, we thank Dr. R.H.L. Disney for
comments on the manuscript.
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Additional information and reprint requests:
Prof. Abu Hassan Ahmad, Ph.D.
School of Biological Sciences
Universiti Sains Malaysia
11800 Penang
Malaysia
E-mail: aahassan@usm.my