Bagrada hilaris (Burmeister) 211
and New Worlds may be due to the bugs’ responses to differences in environmental conditions, incom-
plete evaluations of life stages in some studies, or a combination of these factors.
Many studies on the phenology of Bagrada hilaris have focused heavily on adult populations, so
immature stages often have not been clearly evaluated. In both the Old and New Worlds, adult bugs gen-
erally remain active throughout the year (Batra 1958, Narayanan 1958, Atwal 1959, Sandu 1975, Singh
and Malik 1993, Taylor et al. 2015). In India, Singh and Malik (1993) reported two peaks in adult popula-
tions, one in October and November during the seedling stages of rapeseed (Brassica napus L.) and Indian
mustard [B. juncea (L.) Czern.] and another in March and April at harvest. Also in India, Narayanan
(1958) found adults (and nymphs) most abundant from October through March. He also reported that a
few adults survive the summer heat in crevices in embankments near irrigation channels. In California,
Garrison (2011) reported adults and nymphs feeding on a variety of cruciferous plants in June and
September to November. He also reported that the bugs had spread to the Yuma region of Arizona
and were feeding on Brassica weeds, seed crops, canola, and cotton. In southern California, Reed et
al. (2013b) reported two main population peaks, one from April to May and another from September
to October, with adults overwintering in the soil near host plants. In Arizona, Palumbo (2015a) also
reported similar peaks (March to April and September to October) in adult populations on hosts such
as broccoli and cabbage (B. oleracea). In New Mexico, Bundy et al. (2012) reported nymphs and adults
from several hosts in the Brassicaceae from April through September in 2010 and 2011, shortly after
the bugs became established in the state. More recently (2012–2014), also in New Mexico, Taylor et al.
(2015) found adults and nymphs in the field each month of the year and eggs from February through
October. They also observed that, in the winter months, nymphs and adults could be found near the bases
of senesced host plants in adjacent debris.
Unlike most other stink bugs, Bagrada hilaris appears to spend much of its time off its host plant. In
India, Batra (1958) reported that the bugs moved from mustard hosts to shelter beneath weeds at night
and during the heat of the day. In South Africa, Gunn (1918) reported that nymphs moved from plants in
the late afternoon and during the night, hiding between leaves, in debris of fields and gardens, and under
soil clumps. In southern California, Reed et al. (2013a) reported that the bugs spend more of their time
off the plants in the soil during warm weather. In New Mexico, Taylor et al. (2015) found the bugs com-
monly on the soil near the bases of host plants throughout the year. In a field study in Arizona, Huang
et al. (2013) reported that temperature had a significant effect on populations of adult bugs, with peak
abundance occurring during the warmest time of the day. They also observed that environmental factors
such as humidity, wind speed, and dew point were not good predictors of adult activity.
Bagrada hilaris has been reared under controlled conditions in the laboratory and the egg and nymphal
stages have been described (see Taylor et al. 2015 for a summary). The subcylindrical or barrel-shaped
eggs are cream-colored to light brown when deposited, turning dark pink just before hatching (Figure
3.1B,C). Eye spots and an egg burster are visible as the eggs reach maturity (Rakshpal 1949, Taylor et al.
2015). Eggs are laid singly or in small clusters (Howard 1906; Pruthi 1946; Reed et al. 2013a, b; Taylor
et al. 2014) (See below for details on egg clutch size and ovipositional behavior). The egg incubation
period lasts ≈2–6 days at 28–40°C (Atwal 1959, Batra and Sarup 1962, Azim and Shafee 1986, Singh
and Malik 1993, Rohilla et al. 2004, Ghosal et al. 2006, Deep et al. 2014a). Taylor et al. (2015) reported
an average incubation period of ≈7.5 days at 25°C. Wintertime incubation periods of up to 20 days have
been reported (Mukerji 1958, Bhai and Singh 1961). Atwal (1959) and Deep et al. (2014b) found 100%
egg mortality at 45°C. First instars hatch, with the aid of an egg burster, through the pseudopercular
opening at the cephalic end of the egg (Taylor et al. 2015), a process that may take up to 20 minutes
(Rakshpal 1949).
The five nymphal instars are distinguished by distinct differences in morphology and color (Taylor et
al. 2015) (Figure 3.1E). First and second instars are reddish brown (first instar) to light brown (second
instar) with a red abdomen. Taylor et al. (2015) documented two color morphs of the third through fifth
instars of this species, with differing levels of melanization. These later instars often take on the bright
red, black, orange, and white markings of the adults. Fourth and fifth instars are distinguished by the
presence of wing pads, distinctly evident in the fifth instar.
Singh and Malik (1993) reported total nymphal stadia of 14–22 days, 14–20 days, and 29–37 days
under temperatures of 25.5–34°C, 28–30°C, and 28°C, respectively. Taylor et al. (2015) reported average