Fine structure of the pygidial glands of Bledius mandibularis (coleoptera : staphylinidae)

The pygidial glands of B. mandibularis produce a mixture of terpenes, fatty acid derivatives, and a benzoquinone. The morphology of these glands is described with particular attention to the ultrastructure of the secretory cells and their efferent ductules. Each functional secretory unit consists of two secretory cells (cortical and medullary) both of which are associated with a common extracellular cuticular ductule. The fenestrated tip of the ductule lies in a cavity bounded by the invaginated plasma membrane of the cortical cell; within the cavity surrounded by the medullary cell, the ductule is divided into a bulb region (where a spherical mass of fine cylinders surrounds the ductule itself) and an unfenestrated switchback region. Inflated cisternae of rough endoplasmic reticulum, filled with flocculent material of low electron density, are abundant in the cortical cytoplasm, and presumably represent primary secretory product en route to the cavity of this cell. The plasma membrane bounding this cavity is much infolded, and the inner surface of this membrane is studded with fine particles. In contrast, few cisternae are inflated in the medullary cell and the corresponding infolded plasma membrane is smooth. The manner in which both cells may cooperate to produce the heterogeneous secretory product is discussed.     

The mycetophagidae (coleoptera) of the maritime provinces of Canada

The Mycetophagidae (hairy fungus beetles) of the Maritime Provinces of Canada are surveyed. Seven species in the genera Mycetophagus, Litargus, and Typhaea are found in the region. Six new provincial records are reported including Mycetophagus punctatus and Mycetophagus flexuosus, whichare newly recorded in the Maritime Provinces. The distribution of all species is mapped, colour habitus photographs of all species are figured, and an identification key to species is provided. The discussion notes that four of the species found in the region are apparently rare, possibly due to the history of forest management practices in the region; a situation similar to that of a significant proportion of other saproxylic beetles found in the Maritime Provinces.     

Cuticular hydrocarbons of adult Blaps mucronata latereille (coleoptera: tenebrionidae)

• 1.1. The cuticular hydrocarbon mixture of Blaps mucronata comprises n-alkanes (C₂₃ to C₂₉, 41%), 3-methylalkanes (C₂₄ to C₃₂, 29%) and internally branches monomethylalkanes (C₂₄ to C₃₆, 11%) and dimethylalkanes (C₃₂ to C₃₇, 15%).
• 2.2. B. mucronata is distinguished from six other tenebrionid species by the qualitative and quantitative characteristics of its hydrocarbon mixture.

     

The early embryology of Diabrotica undecimpunctata howardi (coleoptera: Chrysomelidae)

Early embryogenesis is described for the southern corn rootworm, Diabrotica undecimpunctata Howardi Barber, at 24 ± 1°C. During the first four hours following oviposition, the maturation divisions and syngamy are completed. Morphological changes in the second polar body accompany syngamy. Cleavage divisions and energid migration occur during the fourth to the tenth hour. The vitellophags, which appear during cleavage divisions, are distinguished from the blastema-bound nuclei by having smaller, more densely staining nuclei. After completion of a uniform blastoderm (11-14 hour), cell division ceases until the completion of the germ band and the formation of the embryonic membranes (22 hour). This species has a pattern of amnion formation that is different from most Coleoptera but is shared with a few other chrysomelids, some Isoptera, and some Odonata.     

Humidity-invoked upwind orientation of shore insects (Bambidion obtusidens, coleoptera: Carabidae)

Because insects cannot rely solely on kinetic responses to locate upwind humidity resources, an alternative mechanism involving the perception of windborne humidity fluctuations was investigated. In a wind tunnel, upwind responses of adult shore insects (Bembidion obtusidens Fall, Carabidae, Coleoptera) were invoked by pulsed (1.25-Hz) increases (1.7%) of relative humidity at ambient relative humidities of 32, 42, 52, and 62% but not at 72 and 86%. Conversely, upwind responses to pulsed decreases (1.8%) occurred at 65, 72, and 86% but not at 32, 42, and 52% ambient relative humidities. These results suggest that perception by moist-air and dry-air hygroreceptors of turbulence-induced pulses of moist air or of dry air in their habitat trigger positive anemotactic orientation of these insects to upwind humidity resources.     

Differential vitamin and choline requirements of symbiotic and aposymbiotic s. oryzae (coleoptera: curculionidae)

• 1.1. Development times, fertilities and weights of symbiotic and aposymbiotic strains of the rice weevil Sitophilus oryzae in response to single omissions of seven vitamins and choline were studied.
• 2.2. No strict requirement for choline could be demonstrated: development times and weights were comparable to diets with or without choline, but the presence of choline increased fertility of the symbiotic strain on vitamin-deficient diets.
• 3.3. The 0.02% concentration used in these experiments may be too high since it resulted in a lower fertility of the aposymbiotic strain.
• 4.4. The results indicated that niacin could be synthesized by the weevils.
• 5.5. Thiamine, folic acid and pyridoxine were found to be required in the diet of both strains but the latter two may be supplied in part by symbiotes since a first symbiotic generation was obtained.
• 6.6. Pantothenic acid, biotin and riboflavin were only required by aposymbiotic weevils: their omission from the diet did not modify the development of symbiotic insects.
• 7.7. It is therefore suggested that these three vitamins are supplied by symbiotes.

     

Maintenance of midgut epithelial cells from dendroctonus valens (coleoptera: Scolytidae) in vitro

This article describes the culture of epithelial cells from anterior and posterior midgut regions of adult Dendroctonus valens. Culture conditions were established, and cell adherence was improved by means of a new technique that allowed the cells to grow between two glass coverslips. Cytoplasmic projections occur as anterior midgut cells grow to confluence; these projections were not observed in cells of the posterior midgut. The optimal culture medium for the maintenance of these epithelial cells was Roswell Park Memorial Institute 1640 medium at 25 degrees C. Cells in Grace's medium died in 24 h. Cultures did not require CO(2) atmosphere, but culture development was favored by the microaerophilic environment and the dark conditions in which the cells were grown, between the coverslips.     

An established cell line from the beetle, Xylotrechus pyrrhoderus (coleoptera: Cerambycidae)

Summary A continuous cell line has been established from larval fat body tissues of the cerambycid beetle Xylotrechus pyrrhoderus Bates. These cells were cultured in MGM-450 medium. The cell line, designated as XP-1, showed a heterogeneous population consisting of spherical and spindle-shaped cells with some capacity to adhere and a doubling time of 5 d. The chromosome number of the cell line ranged from 18 to 42 with a mode of 20. Isozyme analysis showed that the cells had patterns distinctive from those of other insect cell lines. The cells were sensitive to insect hormones, and when continuously treated with 20-hydroxyecdysone and juvenile hormone, they assumed a floating elongated-spindle shape and became strongly adherent, respectively.     

Characterization of the esterase isozymes of Ips typographus (coleoptera,scolytidae)

Four esterase isozymes hydrolyzing α-naphthyl acetate (α-NA) were detected screening whole body homogenates of larvae and adults of Ips typographus by electrophoresis. Two of the four isozymes (isozymes 3 and 4) were not detected by α-NA staining in the pupal stage, but topical application of juvenile hormone III (JH III) on the pupa induced these isozymes. The JH esterase (JHE) activity on the gel was associated with the proteins of isozyme 2. The compounds OTFP, PTFP, and DFP inhibited this catalytic activity of isozyme 2 on the gel at low concentrations, whereas the proteins of isozyme 3 and 4 were affected only at higher concentrations. A quantitative developmental study was performed to characterize which of the esterases hydrolyzed JH III, using a putative surrogate substrate for JH (HEXTAT) and α-NA. The I₅₀ of several esterase inhibitors and the JH metabolites were also defined. All findings supported the results that a protein associated with isozyme 2 is catabolizing JH and that isozymes 3 and 4 are the main contributors to the general esterase activity on α-NA. The JHE from Tenebrio molitor was purified by affinity chromatography. Although the recovery was low, an analytical isoelectric focusing gel showed that the JHE activity of the purified enzyme. T. molitor cochromatographed at the same pl as the JHE activity of I. typographus. Arch. Insect Biochem. Physiol. 34:203–221, 1997. © 1997 Wiley-Liss, Inc.     

Pupation by Viburnum leaf beetle (coleoptera: chrysomelidae): behavioral description and impact of environmental variables and entomopathogenic nematodes

Pyrrhalta viburni (Paykull), a new landscape pest in the United States, feeds in both the larval and adult stages on foliage of plants in the genus Viburnum. The insect is univoltine, with larvae active in spring and adults throughout the summer months. Experiments were conducted to determine the depth of pupation in the soil; the impact of substrate texture, moisture content, and temperature on pupation success; and ability of entomopathogenic nematodes to kill larvae when they enter the substrate to pupate. Larvae burrowed only a short distance into the substrate when pupating; 97-100% were found within the top 3 cm of a column of soil or sand and soil mixture in the laboratory. Larval mortality before pupation was low at 22 degrees C but considerably higher at 30 degrees C; at both temperatures, pupation success was lowest on a mixed substrate and higher (and equivalent) on sand or soil alone. Survivorship to adult was influenced by both temperature and substrate moisture content; at 22 degrees C, 56% percent of pupating larvae emerged as adults at 75% moisture content compared with only 25 at 25% moisture content. Emergence of adults was negligible at 30 degrees C, regardless of moisture content. Heterorhabditis bacteriophora and Steinernema carpocapsae were very effective biocontrol agents in laboratory bioassays, reducing adult emergence by 76-100%, with nematode applications made before pupation being more effective than those made after pupation, and H. bacteriophora consistently (but not significantly) more effective than S. carpocapsae. Management methods that take advantage of pupation behaviors are discussed.