FNZ 47 - Erotylidae (Insecta: Coleoptera: Cucujoidea) - Methods and Conventions
Leschen, RAB 2003. Erotylidae (Insecta: Coleoptera: Cucujoidea): phylogeny and review. Fauna of New Zealand 47, 108 pages.
(
ISSN 0111-5383 (print),
;
no.
47.
ISBN 0-478-09350-0 (print),
).
Published 05 Jun 2003
ZooBank: http://zoobank.org/References/F7BD20B2-D210-4D51-9CB2-1BC51DF75F2C
Material examined and general methods
This study is the continuation of a project initiated during work on Cryptophagidae (Leschen 1996). In contrast to the previous study, I have not attempted to examine every species of languriid in detail because of time restrictions. Type species of most genera were examined externally (except for Languriinae) for a previous study (Leschen & Wegrzynowicz 1998), and a few others were examined more recently. Over the years, museum specimens on loan and those retained from identifications have provided the foundation for understanding the morphological variation necessary to determine the monophyly of the higher taxa and some genera. Approximately 400 species of cucujoids have been dissected for this and other studies and an annotated list of dissected species is provided in Appendix 1. Collections and curators are cited in Leschen (1996) and important and additional material examined in this work were borrowed from the collections listed in the Acknowledgments.
In the descriptions of New Zealand species, diagnostic characters are not repeated in the body of the description and two-letter codes on labels and for New Zealand distributions follow Crosby et al. (1998). Total length of the beetle is measured from the anterior edge of the pronotum to the apex of the elytra. Lectotype designation was necessary for Loberolus cursor Grouvelle, Xenoscelis prolixus Sharp (= Hapalips), and New Zealand species described by Broun because holotypes were not designated in the type series. Paralectotypes were designated for New Zealand taxa, because original type material, especially Broun syntypes, are contained in the BMNH and NZAC. Type specimens are listed under each species, while material examined is listed in Appendix 3.
Adult morphology is the focus of this study, and to properly evaluate cladistic and taxonomic characters slide-mounted specimens are mandatory for examination with a compound microscope. Duplicate specimens (especially males) stored in glycerine such that the structures can be rotated easily are also important. Specimen preparation and dissection follows that of Leschen (1996) and was influenced in a large part by methods used by A. Newton (FMNH). There is no quick and easy way to prepare a specimen for light microscopy. Perfect and intact specimens of the species to be dissected are best. Observations of the specimens throughout the preparation process is necessary so that they are not damaged. The specimen should be removed from its paper point or card by placing the specimen into a test tube with a small amount of water and holding the tube over a flame until the specimen floats off (the "Slipinski method"). A piece of cotton inserted at the top will prevent the specimen from boiling out in case of overheating. The wings are removed from the softened specimen and stored in glycerine. The body is placed in weak potash (10% KOH) for maceration of soft tissues, a technique that was advocated by 19th Century coleopterist George H. Horn, and deemed unsafe by David Sharp (Zimmerman 1993). Maceration requires 1 to 4 days, maybe longer depending on the size of the beetle. After maceration, specimens with darkly pigmented cuticle are placed in hydrogen peroxide for a period of up to 5 minutes for further clearing. Once clearing is completed washing in distilled water is necessary to stop the clearing or macerating process. While some entomologists prefer xylene-based mounting media, I prefer alcohol-based mounting media which makes transfer between alcohol preservative, stains, and mounting media easy and practical. After clearing and washing, specimens are transferred to 90% ethanol prior to staining in Chlorazol Black. Staining often requires washing or staining repeatedly until the membranes are clearly visible. To destain, the specimen can be diluted in alcohol until the desired level of penetration is made. The treatment of wings requires special attention to see the veins (Kukalová-Peck & Lawrence 1993) and I do not stain them because these are visible using Nomarski differential contrast under the compound microscope. The wings are removed from the glycerine, washed in water, and placed in graded series up to 90% alcohol. Wings and the rest of the beetle are washed briefly in alcohol and placed directly into the mounting media on a microscope slide where dissection is performed.
Specimens are dissected in Euparal (Chroma-Gessellschaft) mounting medium. A droplet of Euparal is placed on one end of the slide (making room for labels) and the specimen is placed in it. For dissecting tools, two wooden applicators with minutens attached apically are used to disarticulate the specimens. Just as entomologists are idiosyncratic about the way they dissect, likewise each beetle group requires certain procedures. Some groups dissect well and require less finesse, while others are difficult and require patience. Erotylidae are not difficult to manage because their bodies are relatively hard and the sclerites do not distort during dissection. I start with the head by removing the mouthparts and usually keep one mandible and maxilla attached and articulated. The left legs are disarticulated from the body at the coxa, and the genitalia and terminalia are removed. Then the parts are arranged sequentially on the slide and the dissection is laid aside for a period of 3-6 hours while the Euparal sets. The specimens are periodically checked so that the pieces are arranged appropriately until stable. Arrangement of the structures is made with forceps dipped into alcohol (to break the surface skin). Removal of bubbles from the Euparal is done by applying the tips of a closed forceps dipped in alcohol to the edge of the bubble. After setting, four vinyl slide props are set into the media and the slide is placed on a slide warmer set at 40°C for 24 hours. Once hardened, Euparal is applied to the dissection, an 8 x 8 mm cover slip is applied on top of the dissection and the slide dried for a period of 2-4 weeks depending on the thickness of the mount. Slide ringer is not necessary. Disarticulated specimens can easily be removed from the slide mounts by soaking them in a bath of alcohol for approximately 15 minutes.