The shield-backed bug, Pachycoris stallii: Description of immature stages, effect of maternal care on nymphs, and notes on life history

Abstract

The life history of the shield-backed bug, Pachycoris stallii Uhler (Heteroptera: Scutelleridae), immatures was studied on its host plant, Croton californicus Muell.-Arg. (Euphorbiaceae), in Baja California Sur, Mexico. Immature stages are described and illustrated. Pachycoris stallii is bi- or multivoltine and occurs in xeric areas with sandy soil where it is rarely encountered away from C. californicus. Nymphs and adults feed on seeds within C. californicus fruit. Bugs oviposit on the underside of leaves, and females guard their eggs and first-instar nymphs from natural enemies. Embryonic orientation of prolarvae is nonrandom; each embryo is oriented with its venter directed toward the ground. This orientation may facilitate aggregation of first instars. The longitudinal axes of eggs are always oriented upward at about a 16° angle of deviation from a line perpendicular to the leaf surface. This is the first recorded observation of this phenomenon in Pentatomoidea. Experimental removal of females guarding first instars results in 100% loss of nymphs, and this is attributed to disruption of the aggregative behavior of nymphs. Maternal guarding appears to be a net benefit to P. stallii, despite possible costs to the brooding female.

Development ofPachycoris torridus(Hemiptera: Scutelleridae) onJatropha curcas(Euphorbiaceae),Psidium cattleianum(Myrtaceae) andAleurites fordii(Euphorbiaceae)

“…First instar nymphs continue under oviposition, protected by the mother, who provides maternal care until the 2nd instar, second instars display gregarious behavior as they search for food. Similar behavior was observed for other species of Scutelleridae Pachycoris klugii Burmeister,1835 and Pachycoris stallii Uhler, 1863 (Peredo 2002;Williams III et al 2005).…”

Shield Bugs (Scutelleridae)

“…(2015) have collected large numbers of New World scutellerids at butterfl y traps baited with putrefi ed fi sh carrion. Maternal care has been described for A. fl avolineata (Paleari 1992b ), P. torridus (Hussey 1934 ;Santos et al 2005 ), P. klugii (Cervantes-Peredo 2002 ), and also P. stallii Uhler (Williams et al 2005 ). Females guard their eggs and fi rst instar nymphs and may transmit aggregation semiochemicals to fi rst instar nymphs.…”

“…In Galeacius martini Schouteden, eggs are reddish brown, with the surface of the chorion translucent, nearly smooth under light stereomicroscope, and with a mean of 24 aero-micropylar processes (Bianchi et al 2011 ). Studies employing scanning electron microscopy (SEM) for Neotropical fauna are available for Pachycoris stallii (Williams et al 2005 ) and Galeacius martini (Bianchi et al 2011 ).…”

Morphology of the Nymphs ofEuschistus convergens(Hemiptera: Pentatomidae)

“…The function of the abdominal ventral plates' comb-like projections is unknown. Abdominal ventral plates are found also in Scutelleridae (Hussey 1934;Peredo 2002;Williams et al 2005;Bianchi et al 2011b), but are covered by stout projections, allegedly used in vibrational communication between nymphs and adults.…”