Fun Friday Beetle

No time for a full post today but here is a beautiful little guy to satisfy your Coleoptera cravings till Monday. A nice series of these guys came to the black light in SE Texas a couple of weeks ago. I would love to know how the beetle benefits from having such dense and relatively long setae. I haven't keyed this guy out but his overall appearance makes me think that he will by Staphylinidae in the subfamily Scydmaeninae.

Beetle Anatomy

Insects exchange gases through a respiratory system that is made up of spiracles, trachea, and tracheoles. Spiracles are the openings to the atmosphere and they connect to the trachea and eventually tracheoles. The tracheoles are the smallest tubes of the arthropod respiratory system and are the site of gas exchange. The concentration of trachea and tracheoles is highest in those tissues that are most metabolically active like the alimentary canal. The two pictures below show the branching trachea found supplying the alimentary canal of a Tenebrionidae larva.

Trachea supplying the alimentary canal

Coleoptera Trachea

To get these pictures I dissected the larva by first submersing it in insect saline solution which is made by mixing .9 grams of NaCl with 100 ml of distilled water. I then used micro-scissors to slice open the dorsal side of the body and minuten nadelns to hold the sclerites away from the body so that the internal organs could be seen. For my first dissection of a small larva I feel that it went well.

These pictures were taken as part of my goal to build up a collection of photos that I can use in teaching entomology in the future. I used the same Nikon SMZ1500 scope with a Nikon Digital Sight DS-Fi-1 camera to take these photographs that I use for almost everything on this blog. As always I used gimp and combine ZP for the editing process.

Davy Crockett Collecting Trip

I recently made a short collecting trip to Davy Crockett National Forest. The weather was not ideal it rained intermittently and when the rain stopped the moon was out in full force. None the less the black light did bring in a few interesting things including a couple of beautiful extra large Strategus. However, some of the little things were just as amazing like this small dytiscidae belonging to the genus Thermonectus.

Looking at this guy under the scope reminded me of the evolutionary novelty that beetles exhibit that has always been a source of wonder to me. The protarsi of some male Dytiscidae like this one have an amazing array of suction cups that increase the gripping power of the beetles front legs. Most books say that these are used to allow the male to grasp the female during mating. This seems like a plausible explanation though I could not find any publication of an experiment actually testing this idea. Whether it is important in mating or in prey manipulation it is none the less an amazing structure to evolve in an organic form.

A lot of other beetles with aquatic affinities showed up like this Limnichidae with really cool pronotal excavations for the antenna. The species on this one is Physemus minutus. Thanks to the bug guide users who helped me on that identification!

This close up shows a slightly better angle and enlargement for both the excavation that receives the antenna and the setae filled pit in front of the eye.

Another Limnichidae that I have not yet identified has an amazing suit of iridescent bronze and silver setae.

The carabid Tetragonoderus (peronoscelis) latipennis also showed up at the light. This beetle behaves much like a nocturnal tiger beetle often hunting along sandy shores at night. During the day they normally are hidden in leaf litter.

Lots of other interesting but small guys came to the light so if I cant get some IDs I'll have more to post.

Slime Flux and Identifying Nitidulidae

Lobiopa insularis and a typical slime flux

I am working on a project this summer to document the beetles that make use of slime flux habitats. These are wet tree wounds that are unable to heal over due to infection by numerous bacteria and fungi that are toxic to the wood. Because of this they can last for many years and provide a great habitat for many diptera and coleoptera.

Very little work has been done on this habitat. Sokoloff discussed what he found in this habitat and compared it to the species collected in bannana traps. However, his work was all done in one place during one summer in California. Furthermore, his focus at the time was primarily on Drosophila. In the realm of beetles there have been a few papers that mentioned the habitat as the obligatory niche for Nosodendron unicolor. As well as a cursory description by Brett Ratcliffe from 1970 saying that he collected a great assortment of beetles at a slime flux in Japan. I decided that documenting beetle diversity in this habitat would be a good side project to work on this summer and it gives me an excuse to do some extra collecting.

As much fun as the collecting is the real work is in identifying all of the specimens that I am finding. Not surprisingly one of the most common families that I have been running into is Nitidulidae. To identify these guys I am starting out with the key in American Beetles this gets me to the genus but from their it is a bit tougher. Below are the references that I have been using with some success. If you have any pointers to an important paper that I have missed please let me know.

Parsons, C.T. 1943. A Revision of Nearctic Nitidulidae (Coleoptera) Bull. Mus. Comp. Zool. 92(3):121-278

Parry, R.H., H.F. Howden. 1975. A New Species of Colopterus from Florida (Coleoptera, Nitidulidae) Coleopterists Bull. 29(4): 275-279

Connell, W.A. 1984. Nearctic Nitidulidae-synonymy and additions since Parsons' revision. Coleopterists Bull. 38(2):160-164

Cline, A.R. 2003. A new sap beetle (Coleoptera: Nitidulidae) to the United States with a revised key to the Camptodes Erichson occuring in America North of Mexico.

Connell, W.A. 1977. A key to Carpophilus sap beetles associated with stored foods in the United States. Cooperative Plant Pest Report 2: 398-404.

Also the websites:

Nitidulidae in the Mississippi Entomological Museum

and

Kateretidae and Nitidulidae of Wisconsin