Life cycles of Helicoverpa armigera and H. punctigera
Life cycles of both H. armigera and H. punctigera take about 73 days (in absence of pupal diapause) in spring or autumn with average temperature of 16 – 18°C from eggs to adults, whereas in summer the life cycles take about 34 days with average temperature of 28°C from eggs to adults (Zalucki et al. 1986). Since both life cycles are relatively similar, details on both life cycles can be merged into one. Below is the details on characteristics of eggs, larvae, pupae and adults and life cycles of H. armigera (Figure 3) and H. punctigera (CABI, 2013):
Figure 3: Life cycles of H. armigera
(Images are not according to actual sizes)
Image courtesy of A.M. Varela, icipe extracted from http://www.infonet-biovision.org/default/ct/76/pests
(Images are not according to actual sizes)
Image courtesy of A.M. Varela, icipe extracted from http://www.infonet-biovision.org/default/ct/76/pests
Eggs:
Figure 4: Yellowish white colour showing eggs are newly laid
(Image is not accoding to actual size)
Image courtesy of A.B.S. King extracted from http://www.cabi.org/cpc/bigimage.aspx?imageURL=portfolio/compendia/Normal/helarm01.img
Newly laid eggs are characterised by yellowish white colour (Figure 4). Colour changes from yellowish white to dark brown after few days. Eggs are spherical-shaped with diameter of about 0.4mm to 0.6mm. When eggs are close to hatching, black head capsule is visible through the eggshell.
Larvae:
Figure 5: H. armigera larva found in tomato
(Image is not according to actual size)
Image courtesy of A.B.S. King extracted
from http://www.cabi.org/cpc/bigimage.aspx?imageURL=portfolio/compendia/Normal/helarm11.img
Larvae of H. armigera and H. punctigera undergo 6 or 7 developmental growth stages before developing into pupal stage. The neonate (newly hatched) larvae may grow up to 7mm long, with yellowish-white to reddish-brown colour and dark-spotted body. The dark spots on the body is due to the dark coloured spiracles and tuberculate bases. Neonate larvae usually eat soft leaves, flowers or flower buds, moving about their feeding sites. Moulting occurs when larvae are about to develop into following larval stage. Subsequent larval instars may grow up to 40mm long, showing distinctive characteristics: brown head; pale brown prothoracic and supra-anal plates and legs; black claws and spiracles; small tubercles on skin surface and crochets on prolegs are arranged in arc (Figure 5). Full-grown larvae may have variable colour and markings on the body. Hence it is rather difficult to determine the species identity at this stage. It is the late larval stage that causes damage to crops by consuming the affected plant parts. Larvae shift from foliar feeders to developing seeds and fruits as larval instar development progresses (Reed & Pawar 1982).
Pupae:
Figure 6: H. armigera pupa which is found in the soil
(Image is not according to actual size)
Image courtesy of http://helicoverpa.org/random_images/1
When the last larval instars are about to become pupae, the larvae will burrow and enter the soil to pupate. Pupae are characterised with 14-18mm in length, brown smooth surface and rounded anterior and posterior (Figure 6). Not all pupae will develop into adults without pupal diapause. The period of pupal diapause varies and highly dependent on temperature and photoperiod (Hackett & Gatehouse 1982).
Adults:
Figure 7: (a) Adult H. armigera with red circles showing pale patch on darker region of hind wing (distinctive feature); (b) Adult H. punctigera with blue circles showing no pale patch on darker region of hind wing
(Images are not according to actual sizes)
Image courtesy of (a) V.V.Neymorovets (VIZR) extracted from http://www.agroatlas.ru/en/content/pests/Helicoverpa_armigera/
(b) the Macleay Museum, University of Sydney extracted from http://lepidoptera.butterflyhouse.com.au/heli/punct.html
Adults H. armigera and H. punctigera are characterised with fine hairs antennae; wingspan of 35-40mm; tapered thorax with 14-18mm long; orange-brown forewings (female) or greenish-grey forewings (male); and pale brown hind wings. Adults H. armigera have distinctive feature whereby a pale patch is observed near centre of the dark region, as indicated by red circles (Figure 7a). In contrast, adults H. punctigera do not have any pale patch at the centre of the dark region, as shown in blue circles (Figure 7b).