Abstract Hemisarcoptes cooremani (Thomas) (Acari: Hemisarcoptidae) is native to the southern United States, from California to Florida. Parasitic stages of the mite's life cycle (i.e. larvae, protonymphs, tritonymphs and adults) have been used for the biological control of diaspidid scale insects which infest perennial vascular crops. A heteromorphic dispersal stage (hypopode) differs from all other stages in the life cycle in that it is well sclerotized. All other stages are relatively soft-bodied and sheltered from desiccation by the cap (and velum) of their invaded diaspidid prey. The hypopode lacks an oral cavity and foregut and is therefore prevented from imbibing water, as water becomes available from the environment, and as it awaits the arrival of its phoretic dispersal host (Chilocorus cacti). A water balance profile was constructed on the hypopode of H. cooremani to better understand how this stage survives extended periods of water stress in hot dry climates. A high dehydration tolerance was not apparent. The major survival element in dry environments appears to be water retention (low net water loss rate) and a small water pool. The high critical transition temperature and suppressed activation energies for water loss suggest that the enhanced water conservation is due, in part, to the sclerotized cuticular armor, particular to this stage in the life cycle.
L'Ontogenèse et le Concept de Stase chez les Arthropods/Ontogeny and the Concept of Stase in Arthropods Get access L'Ontogenèse et le Concept de Stase chez les Arthropods/Ontogeny and the Concept of Stase in ArthropodsAndré H. M. Lions J.-Cl. [eds.] AGAR Publishers, Wavre, Belgium, 1989 158 pp., $59 ISBN: 2-87257-001-2 Marilyn A. Houck Marilyn A. Houck Department of Biological Sciences Texas Tech University Lubbock, Texas 79409. Search for other works by this author on: Oxford Academic Google Scholar Annals of the Entomological Society of America, Volume 85, Issue 3, 1 May 1992, Pages 355–356, https://doi.org/10.1093/aesa/85.3.355 Published: 01 May 1992
Abstract Large numbers (up to 400/elytron) of heavily sclerotized deutonymphs of the mite, Hemisarcoptes cooremani, attach to the elytral hypodermis of desert-inhabiting beetles, Chilocorus cacti, for transport and feeding. A potential physiological benefit to beetles of tolerating attached mites in dry habitats may be a reduction of the surface area-to-volume ratio of exposed evaporatory tissue (decreased water loss), especially during flight. In this study, infested beetles were observed to have identical water balance characteristics as nonparasitized beetles, indicating that mites provide no extra, mechanical advantage to the beetle in terms of increased water conservation. The beetles were not distinguished by having a low water content, high tolerance for dehydration, or ability to absorb water vapor from the atmosphere. Their ability to retain water (low net water loss rate that compares favorably to values for diapausing beetles that maximize water conservation during quiescence), however, helps adapt them to a dry environment, supports the behavior of reflex bleeding, and probably aids in the toleration of their interaction with Hemisarcoptes.
Desmognathus f. fuscus and Desmognathus o. ochrophaeus were individually desiccated to a critical activity point in an air flow apparatus. In both species the rate of water loss was inversely correlated with body weight, the time to reach the critical activity point (CAP) was positively correlated with body weight, and tolerance to water loss (percent initial body water lost at the CAP) was positively correlated with body weight. I nterspecific comparisons revealed that D. f. fuscus of larger mean body size lost water significantly slower than D. o. ochrophaeus, showed no significant difference in time to the CAP than D. o. ochrophaeus and tolerated significantly less body water loss than D. o. ochrophaeus. When groups of similar mean body size were compared, D. f. fuscus lost water at approximately the same rate as D. o. ochrophaeus, took a significantly shorter timance to reach the CAP and showed si cantly less terance to water loss than the more terrestrial D. o. ochrophaeus. * * *
Principal component analysis revealed sexual dimorphism in wing forms of the sweetpotato whitefly, Bemisia tabaci (Gennadius); fore- and hindwings of females were larger than those of males. Discriminant function analysis indicated subtle morphological differences within the same sex between the wings of migrators and the wings of those engaging only in trivial flight. These differences suggest that B. tabaci employs dispersal strategies used by other dimorphic Homoptera that occupy heterogeneous habitats. Identification of migrating and trivial flying morphs among B. tabaci will be useful in developing a better understanding of the migrational patterns of these insects.
A new hexacyclic alkaloid, chilocorine C (4), has been isolated from Chilocorus cacti and characterized on the basis of its IR, UV, MS, and NMR data. Although its structure is closely related to that of exochomine (1) (isolated from Exochomus quadripustulatus) and to chilocorine A (2) and B (3) (obtained previously from C. cacti), the presence of a hydroxymethyl substituent on the saturated tricyclic moiety represents an unexpected structural variation on the dimeric alkaloid theme.
