Isolation and morphological study of ecologically-important insect “Hermetia illucens” collected from Roorkee compost plant

INTRODUCTION
Black Soldier Fly (BSF) was first reported
in 1930 in Hillo sugar companies in
Hawaiian Islands (Duponte & Larish,
2003). Scientifically known as Hermetia
illucens, it belongs to the phylum
Arthropoda, class Insecta, order Diptera
and family Stratiomyidae and is spread in
tropical and warmer climatic regions
around 45°N to 40°S latitude (Üstüner et
al., 2003); however, it is believed that it
originated from America (Callan, 1974).
This fly is seen quite rarely in North India
(Ashuma et al., 2007). There have been
many studies around the globe, on the
utilization of BSF larvae for the treatment 

of organic waste on which voraciously
(Sheppard et al., 1994; Li et al., 2011a; Li
et al., 2011b; De Marco et al., 2015; Diener
et al., 2011a; Diener et al., 2011b).
Traditional landfill composting takes
years to decompose organic waste, whereas
vermiculture reduces it to 3 months;
nonetheless, BSFL can decompose and
valorize organic waste in a week, thus
reducing the overall process time
significantly. Various researchers have
found these larvae in composts (Gujarathi
& Pejaver, 2013). BSFs lack chewing
organs in their mouth, only posses a
sucking tube, which is the reason they only
drink water during their adult stage and
survive on their own fat 

Fig. 1. Images of BSF at various stages of its life cycle reported by other researchers: (a) Adult (b) Larvae
(Gujarathi & Pejaver, 2013) (c) Pupae (Li et al., 2016)
and protein, stored from their larval stage.
Figure 1 shows the photographs of adult fly
and larvae as reported by other researchers.
The larvae develop through 6 larval
instars, usually growing to 18-20 mm in size
(Rozkosny, 1997). Artificial breeding of BSF
has been reported to be quite challenging and
requires controlled temperature, humidity
and light intensity for each stage of its life for
successful completion of its life cycle. The
present study reports for the first time
sighting of BSF at Roorkee in the state of
Uttarakhand, India, located in the foothills of
Himalayan mountains. We also report
morphological images of BSF larvae, pupae,
and adult, using Field Emission Scanning
Electron Microscopy (Fe-SEM).
MATERIALS AND METHODS
BSF pupae were recovered from an old batch
of compost in a bushy area. Afterwards, a
compost trap, made up of food waste, cow
dung, and saw dust, was set in the area from
which a sum of 200 BSF larvae were
recovered (Fig. 2). The collected larvae were
fed on Gainesville diet and reared in the
insect-rearing unit located indoor. After 12
days of organic waste feeding, the larvae
turned into pupae, about 30mm in size, from
an initial length of 6 mm. The average
temperature and humidity was 30±2°C and
60±5%, respectively during the entire
experiment and the flies emerged from about
30% of the total pupae. In a similar manner,
BSF larvae are still being harvested through
setting up of compost traps and further trials
are being carried out for waste reduction.
Figure 2 shows the life cycle of the BSF as
observed in our laboratory and also an
enlarged image of larvae feeding on organic
substrates.
For Scanning Electron Microscope
(SEM) imaging, individual samples of
larvae, pupae, and fly were stored at -20°C,
later to be taken out and washed with 70%
ethanol solution, and the samples received no
other treatment. The specimens were coated
with gold, using a sputter gold coater, and
were examined with FE-SEM (Field
Emission Scanning Electron Microscope
Quanta 200 FEG, Netherlands), the
resolution and magnification was <2nm and
12X-1000Kx, respectively, operating in a
voltage range of 200V-30kV.
RESULTS AND DISCUSSION
The collected BSF larvae, brought from the
compost plant to the insect-rearing unit were
fed on Gainesville diet, to grow up to 30 mm
long. The larvae in the compost heap
consumed the organic waste, developing into
pupae (Fig. 3b) in about 20 days. It took
them at least 14 days (approx.) to become
flies (data not shown). Figures 3, 4, and 5
show FE-SEM images of various life stages
of BSF. 

Fig. 2. (a) Life cycle of BSF, (b) Black Soldier Fly Larvae at IIT Roorkee rearing unit

Fig. 3. SEM image of various body parts of wild BSF larvae (a) the lavae, (b) the head, (c) the mouth part,
(d) the skin with dense hair cover, (e) hair folicles in the hair-covered body, and (f) the thoraic segment

The SEM images of the BSF larvae show
dense hair cover throughout the larva body.
The head is hemicephalic. As already
reported by Kim et al. (2010), H.illucens'
mouth possesses scavenger features. It has a
very well-developed mandibular-maxillary
complex with a pointed labrum. SEM images
of the head and the mouth clearly show the
mandibular brush, maxillary palp, the
antennae, and the prementum. The external
skin, i.e. the exoskeleton, appears to be hard
and porous with visible hair follicles (Fig. 3).
It was also observed that the exoskeleton is
quite resistant to acidic atmosphere, allowing
the larva to survive in pH conditions as low
as 5.
SEM images of BSF pupae are almost
similar to BSF larvae, with the only visible
difference being that the larvae have a
denser hair cover in its body than the pupae
(Fig. 4).
In this study it was observed that the
head of the BSF is composed of dense hair
cover. Also the head of the H. illucens is
very tightly connected to its thorax, while
the mouth is not retracted into the thorax.

Fig. 4. SEM picture of Wild BSF pupae (a) the Thoraic segments; (b) the hair, covering the thoraic
segments; (c) the porous exoskeleton; (d) magnified view of the hair; (e) magnified hair, showing dense
hairy cover; and (f) the Thoraic segment

Fig. 5. SEM picture of adult wild BSF (a) the head, compound eye, and Prothorax; (b) compound eye and
antannae; (c) magnified view of the compound eye; (d) the antannae; (e) the wings; (f) magnified view of
the wings; (g) magnified view of the side edge of wings; (h) magnified view of sub-costa of the wings; (h)
magnified view of the legs; and (i) magnified view of female genitalia
Paulk and Gilber (2006) studied the
external anatomy and physiological
capabilities of Prosternal Organ (PO), i.e. a
head posture proprioceptor, located at the
base of the neck in H.illucens (Fig. 6).
They also observed 130 mechanosensory
hair sets around the PO, which-they
reported- to be determinant in head
movement postures of BSF.

Fig. 6. The prosternal organ in H.illucens: (a) SEM of the ventral cervical region of a female H. illucens;
(b) SEM of the PO region of H. illucens (Paulk & Gilber, 2006)
The compound eye showed homogenous
hexagons. The magnified image of BSF
wings showed dense false hairs on its
surface, almost having a curvature in one
direction and uniformly distributed
throughout the wings. The legs were also
found to be extensively covered by long
hairs.
CONCLUSION
H. iilucens larvae attained a length of 30mm
after 12 days of voracious feeding. The FESEM
analysis shows that several stages of
BSF have a similar attribute of dense hairy
morphology. The mouth of the H. illucens
shows a well-developed mandibularmaxillary
complex, resembling the
characteristics of scavengers, which makes
the insect a suitable candidate for organic
waste consumption. The literature describes
BSF larvae as a potential agent to turn trash
into value added resource in the form of
stored protein, fat, and carbohydrate in its
body mass. The only challenge in this
process is artificial rearing of BSF.
Acknowledgement
This research was funded by the
Department of Biotechnology (Govt. of
India), Biotechnology Industry Research
Assistance Council (BIRAC) and The Bill
and Melinda Gates Foundation (BMGF)
under the grant number
BIRAC/GCI/0066/02/13-RTTC.