Biosystematics of the Dendroctonus frontalis (Coleoptera: Scolytidae) Complex

by Dr. Molly Darr | Jun 17, 2022 | 1981-1990 Publications

Abstract

The validity of Dendroctonus frontalis Zimmerman, D. brevicomis Leconte, D. mexicanus Hopkins, D. vitei Wood, D. approximatus Dietz, and D. adjunctus Blandford as distinct species is supported by breeding experiments, karyology, male genitalia, and external morphology. The most recent synonymies proposed for this group, D. frontalis (=arizonicus Hopkins), D. brevicomis (=barberi Hopkins), and D. adjunctus (=convexifrons Hopkins), are corroborated. D. frontalis from several localities in the southeastern United States, Arizona, and Mexico produced fertile hybrids in all combinations tested. D. brevicomis from Arizona paired with beetles from California produced larvae readily. Pairings of D. mexicanus or D. brevicomis with D. frontalis produced no larvae. No breeding experiments were conducted with D. vitei, D. adjunctus, or D. approximatus. Karyotypes of all species were distinguishable by chromosome number, configuration of sex chromosomes, or size and centric position in autosomes. Male meiotic formulae were: D. frontalis, 7AA + XyP; D. mexicanus, 5AA + XyP; D. brevicomis and D. approximatus, 5AA + neo-XY; D. adjunctus 6AA + neo-XY. D. vitei was not studied cytologically. Seminal rods of male genitalia readily distinguished all species of the D. frontalis complex. Previously described details of the external morphology were insufficient to separate D. frontalis, D. mexicanus, and D. vitei with confidence. Mean pronotal widths differed significantly in all species comparisons except D. brevicomis vs. D. mexicanus. Under strong illumination, the pronotum and elytra of D. vitei were equally pigmented, whereas the elytra of D. frontalis and D. mexicanus were lighter than the pronotum. D. frontalis occurs at elevations of less than 2,000 m on east and west coastal-facing slopes of the Mexican Sierra Madre ranges where its key hosts are Pinus oocarpa and P. teocote. D. mexicanus occurs at 1,800-2,500 m in the central Mexican highlands and in semiarid forests of P. leiophylla and P. montezumae on interior slopes of the Sierra Ranges. The known range of D. vitei is extended to northeastern Mexico; its key host from Central America northward is P. pseudostrobus. D. frontalis apparently occurs frequently in association with D. vitei, but neither species was identified in association with D. mexicanus. The occurrence of D. mexicanus in Central America is not confirmed.

Keywords

Insecta, Dendroctonus frontalis complex, distribution, biosystematics

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Life Cycle of Dendrolaelaps neodisetus (Mesostigmata: Digamasellidae), a Nematophagous Mite Associated with Pine Bark Beetles (Coleoptera: Scolytidae)

by Dr. Molly Darr | Jun 17, 2022 | 1981-1990 Publications

Abstract

Dendrolaelaps neodisetus (Hurlbutt) completed its development in 144 to 312 h at 25°C. Longevity of adults ranged from 14 to 105 days for females and 11 to 113 days for males. After a preoviposition period of 1 to 2 days, females laid an average of 3.38 ± 0.47 eggs per day, with a maximum of 68 for any individual. Hatching varied from 48 to 168 h. Larval and protonymphal instars lasted 24 to 120 and 24 to 96 h, respectively. Some individuals remained in the deutonymphal (phoretic) stage for 6 to 119 days, whereas others molted to adults after 24 to 96 h. All active instars preyed on nematodes

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Seasonal Distribution of Three Common Mite Associates of the Southern Pine Beetle(Coleoptera: Scolytidae) in Central Louisiana

by Dr. Molly Darr | Jun 17, 2022 | 1981-1990 Publications

Abstract

First record of the thrips parasite Goetheana parvipennis (Gahan) (Eulophidae: Hymenoptera) from the Bahamas – Geotheana (=Dasyscapus) parvipennis (Gahan) (identification confirmed by Z. Boucek, Commonwealth Institute of Entomology), described from Java as a parasite of Thrips tabaci Lind., was introduced from West Africa into Trinidad for the control of Selenothrips rubrocinctus (Giard.) in 1935. From Trinidad it was sent to Grenada, Jamaica, Bermuda, Puerto Rico, continental USA, Hawaii and Canada for trial against the same or other thrips. Annecke (1962. South African J. Agric. Sci. 5: 273-9), on the basis of specimens from Venezuela where it had not been released, con- cluded it may have been present in the neotropics prior to the Trinidad introduction. However, it had not been found in Trinidad during extensive pre release collections but was later recovered from several of the release sites. It has had no regulatory effect on populations of its target host S. rubrocincutus on cocoa and cashew (Callan, E. Mc 1943. Bull. Ent. Res. 34: 313-21). On the other hand since its release in Jamaica it has been re-covered regularly as a parasite of this thrips on mango.

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Convenient Synthetic Route to 6,8-Dioxabicyclo octanes, the Aggregation Pheromone Components of Bark Beetles

by Dr. Molly Darr | Jun 17, 2022 | 1981-1990 Publications

Abstract

Convenient syntheses of (±)-frontalin (I) and (±)-brevicomins (Ila) and (Ilb) were achieved from pent-4-en-1 -ol (2) and pent-4-yn-1-ol (3). In a few simple and unambiguous steps, the alkenol (2) and the alkynol (3) were transformed into the acetal bromide (7) and the alkenyl bromides (14) and (17), respectively. Acylation of the Grignard reagents of these bromides provided the corresponding methyl ketones (8), (15), and (18), the key intermediates for the synthesis of the title bicyclic acetals. The ketone (8) was converted into the olefin (9) which, on epoxidation followed by acid hydrolysis, yielded (±)- frontalin, whereas epoxidation of the alkenones (15) and (18) and subsequent cyclisation afforded exo and endo– brevicomin, stereoselectively.

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