Protective Geometry and Reproductive Anatomy as Candidate Determinants of Clutch Size Variation in Pentatomid Bugs.

AbstractMany animals lay their eggs in clusters. Eggs on the periphery of clusters can be at higher risk of mortality. We asked whether the most commonly occurring clutch sizes in pentatomid bugs could result from geometrical arrangements that maximize the proportion of eggs in the cluster's interior. Although the most common clutch sizes do not correspond with geometric optimality, stink bugs do tend to lay clusters of eggs in shapes that protect increasing proportions of their offspring as clutch sizes increase. We also considered whether ovariole number, an aspect of reproductive anatomy that may be a fixed trait across many pentatomids, could explain observed distributions of clutch sizes. The most common clutch sizes across many species correspond with multiples of ovariole number. However, there are species with the same number of ovarioles that lay clutches of widely varying size, among which multiples of ovariole number are not overrepresented. In pentatomid bugs, reproductive anatomy appears to be more important than egg mass geometry in determining clutch size uniformity. In addition, our analysis demonstrates that groups of animals with little variation in ovariole number may nonetheless lay a broad range of clutch shapes and sizes.

Identification of Nymphal Instars of emMecidea/em emmajor/em Sailer and Mecidea minor Ruckes (Hemiptera: Heteroptera: Pentatomidae: Mecideini) from the Southwestern and Central United States.

The mecideine stink bug genus Mecidea is represented in America north of Mexico by three species: Mecidea major Sailor, Mecidea minor Ruckes, and Mecidea longula Stål. M. major and M. minor are widely distributed, occurring collectively from the Midwest to California. M. longula is known only from south Florida. The life histories of M. major and M. minor have been published including laboratory rearing from egg to adult and descriptions of the immature stages. However, no key has been developed for identification of the nymphs of these two species. Here, we present a key to the nymphs of these taxa to the species and instar levels.

Nymphal development of Rhopalus maculatus and Chorosoma schillingii (Hemiptera: Heteroptera: Rhopalidae: Rhopalinae) and development of trichobothrial pattern in Rhopalidae.

The nymphal morphology of the family Rhopalidae is well known for several species, most of which are pests. Ontogenetic changes in morphology are described in detail for two members from two tribes of the subfamily Rhopalinae, Rhopalini: Rhopalus (Aeschyntelus) maculatus (Fieber) and Chorosomini: Chorosoma schillingii (Schilling). Keys to the nymphal instars of both species are provided. The special types of nymphal setae and lateral abdominal processes are described in R. maculatus. The ontogenetic development of abdominal trichobothria is described, and the known trichobothrial patterns within the Rhopalidae are discussed.

Systematic relationship between Piezodorus guildinii and P. hybneri (Hemiptera: Heteroptera: Pentatomidae) and diagnostic characters to separate species.

The pentatomid genus Piezodorus presently contains about 12 species, all of which, with one exception [i.e., P. guildinii (Westwood)], have been reported from the Old World; P. guildinii apparently is limited to the New World. P. guildinii and P. hybneri (Gmelin) are similar in appearance and have been considered by some as sister species. The following characteristics we consider valid as diagnostic to separate the two species: for males, the shape and length of the vesica, differences in the anatomy of the conjunctival appendages and penial plate, and shape of the pygophore and parameres; and for females, differences in the anatomy of the first and second gonocoxae, ninth paratergites, and spermathecae.

Life history of Mecideamajor with descriptions of nymphal instars (Hemiptera, Heteroptera, Pentatomidae).

The life history of the stink bug Mecideamajor Sailer was studied in the southern half of New Mexico primarily from January 2005 through December 2007, and the nymphal instars were described. This species was active throughout the year as adults and nymphs, including the winter months. It occurred on various species of grasses during this time but primarily on Lehmann lovegrass, Eragrostislehmanniana Nees; grama grasses, Bouteloua spp.; and tobosagrass, Pleuraphismutica Buckley. The times of occurrence and abundance of the eggs, nymphs, and adults suggest this species is bivoltine with the possibility of a third generation. Instars can be distinguished by several morphological features including body size and presence and relative development of wing pads.