Photophase influence on the reproductive diapause, seasonal morphs, and feeding activity of Euschistus heros (Fabr., 1798) (Hemiptera: Pentatomidae)

Abstract

Laboratory studies were conducted to verify the influence of photophase on diapause incidence in the Neotropical brown stink bug, Euschistus heros (Fabr., 1798), fed with soybean [Glycine max (L.)] Merrill pods. Nymphs were maintained at three different photophases: 10 h, 12 h, and 14 h, with constant temperature of 25 +/- 1 degree C and relative humidity of 65 +/- 5%. With 14 h, approximately 100% of the adults showed mature reproductive organs; the shoulder (spine) length was significantly greater (2.96 and 2.79 mm for females and males, respectively) than those of bugs maintained at the photophase of 12 h (2.60 mm for females and males) and 10 h (2.59 and 2.53 mm for females and males). At the longer photophase (14 h), E. heros showed better reproductive performance and greater feeding activity than insects reared at 10 h and 12 h; in all photophases bugs tended to reduce feeding from the 1st to the 6th week of life. Body color was considered an unreliable parameter to indicate diapause incidence. However, at 14 h, 60% of the insects were dark brown and 40% were reddish brown. These results indicate that E. heros enters reproductive diapause with photophase of 12 hours or less, showing immature reproductive organs or with intermediate development, with shoulder (spine) less developed and reduced feeding activity.

Phenological and Physiological Changes in AdultPiezodorus guildinii(Hemiptera: Pentatomidae) Due to Variation in Photoperiod and Temperature

“…Ethyl alcohol (70%) was used to clean the abdominal cavity of the insects to allow the best view of the reproductive organs. Females were ranked according to Mourão & Panizzi (2002) in one of three categories: immature = ovaries with no differentiation or no development, and no vitellary constriction; intermediate = ovaries with differentiation with visible chambers and vitellary constrictions with oocytes; and mature = ovaries totally developed with oocytes well-developed. For males the condition of the ectodermal sac (collapsed or expanded) was evaluated according to Esquivel (2009).…”

“…Accumulation of energetic reserves, undeveloped reproductive structures, and changes in size, shape and coloration body, are among the most conspicuous alterations that occur among pentatomids during winter diapause (McPherson 1974;Ali & Ewiess 1977;Ito 1985;Alburquerque 1993;Hodek & Hodková 1993;Kobayashi & Numata 1995;Nakamura & Numata 1997;Musolin & Numata 2003;Mourão & Panizzi 2002;Chocorosqui & Panizzi 2003;Niva & Takeda 2003). In climates with moderate winters, adults of some heteropterans continue feeding (Shearer & Jones 1996;Mourão & Panizzi 2002;Chocorosqui & Panizzi 2003;Saulich & Musolin 2012).…”

“…Studies with different species of pentatomids that evaluated the effect of photoperiod on reproductive diapause, showed that it is induced by a 12-hour or less photophase (Ali & Ewiess 1977;Alburquerque 1993;Hodek & Hodková 1993;Kobayashi & Numata 1995;Nakamura & Numata 1997;Musolin & Numata 2003;Mourão & Panizzi 2002;Chocorosqui & Panizzi 2003;Niva & Takeda 2003). In some species, the photoperiodic response of diapause induction within a range of temperatures is thermostable (Musolin & Numata 2003); however, in other species temperature also plays a role in triggering diapause, modifying the photoperiodic effect (Numata et al 1993;Hodek & Hodková 1993;Kobayashi & Numata 1995;Niva & Takeda 2003;Saulich & Musolin 2012).…”

The reunion of two lineages of the Neotropical brown stinkbug in soybean lands in the heart of Brazil

“…A second hypothesis would be the occurrence of a latitudinal cline for one or more traits 52,53,54 . The species association with environmental gradients should also be considered, given possible differences in traits and adaptions such as reproductive diapause 27,55,56 .…”

“…The dispersal ability of E. heros is not well known, but is considered to be limited, which might be associated with its limited flight activity and diapause behavior 26,27 . This polyphagous pest feeds on Fabaceae, Solanaceae, Brassicaceae, Compositae, and Malvaceae, however, high population densities are often associated with soybean crops 28,29,30,31 .…”