Month: March 2011

Bichos Argentinos #7 – Naupactus xanthographus

/ Ted C. MacRae / 11 Comments

Naupactus xanthographus (South American fruit tree weevil) | Buenos Aires, Argentina

This weevil (family Curculionidae) was one of just a few beetle species that I encountered earlier this month in Buenos Aires, Argentina at La Reserva Ecológica Costanera Sur.  Weevils are, of course, one of the most taxonomically diverse and difficult groups of Coleoptera, making species IDs based purely on photographs quite challenging.  Nevertheless, I am reasonably confident that this individual represents Naupactus xanthographus, or the South American fruit tree weevil.  This name, it seems, has also been applied to a variety of other weevils photographed in South America and posted on the web, but the images I found at a few seemingly more authoratative sites give me confidence that this is the true N. xanthographus.  The narrow form suggests this individual is a male.

The genus, known collectively as “white-fringed weevils” is a large genus of exclusively Neotropical species – several of which have been introduced to North America (e.g., N. cervinus, Fuller rose beetle, and N. leucoloma) and which were, until recently, placed in a separate genus Graphognathus (Lanteri and Marvaldi 1995) (apparently the reduced humeri and lack of metathoracic wings were deemed insufficient for generic distinction).  In South America some of the species have become pests as well, with N. xanthographus becoming a problem for growers of grapes and other fruits and, thus, earning the names “burrito de la vid” (Chile) and “mulita de la vid” (Argentina) (both roughly translating to “grapevine little donkey”).

This was not an easy photograph to get – I found the weevil clinging to the underside of a leaf above my head.  It was impossible to photograph it in situ, so I moved it to a low twig away from other foliage where I could get the black background I desired.  Once moved, however, the weevil just never… stopped… crawling.  Snapping shots of an actively crawling insect is a crap shoot at best – not only are focus and framing more difficult to nail, but subjects photographed while moving almost always have one or two “bum” legs (lifted or cocked out of position).  A number of attempts were required to get a photo I was happy with (save for the slightly clipped antennal tip).  In such situations, I’ve found it best to track the beetle as it moves and as soon as the center focus point of the lens flashes take the shot.  This at least gives the best chance for nailing the focus, and then it’s simply a numbers game to get a shot with good framing and composition and all the body parts well placed.  Of course, I could’ve zoomed out and just cropped to perfection, but this feels a little like cheating – I’d rather put in the time and practice perfecting my game out in the field as much as possible.  An occasional clipped antenna, tarsus, etc. now will lead to better results down the line.

REFERENCE:

Lanteri, A. A. and A. E. Marvaldi. 1995. Graphognathus Buchanan a new synonym of Naupactus Dejean and systematics of the N. leucoloma species group (Coleoptera: Curculionidae). Coleopterists Bulletin 49(3): 206-228.

Bichos Argentinos #6 – Jumping Spider

/ Ted C. MacRae / 19 Comments

I photographed this jumping spider (family Salticidae) two weeks ago in Buenos Aires, Argentina at La Reserva Ecológica Costanera Sur. In gestalt it is very similar to our North American species of the genus Phidippus, but I can’t say for sure whether it actually belongs to that genus. I found it crawling on the foliage of a tree just about eye height, and I’m guessing from the muted markings and roundish shape to the abdomen that it is a female (I saw another individual later that I took to be a male of the same species – it was similarly but more boldly marked and with a much more tapered abdomen). I hope you’ll forgive my hubris, but I’m rather pleased with how these photographs turned out (although, admittedly, there were others that were not so good). In my opinion, they represent further improvement over my first two attempts at photographing jumping spiders (with the standard caveat that I am still no Thomas Shahan). These improvements involve primarily sharpness and detail but also composition, and I consider them to be largely due to lighting and learning how to handle the subject.

The detail in these photos results not only from proper focus, but also lighting techniques. All of these photos were taken hand-held using a Canon MP-E 65mm macro lens at f/13 with full flash lighting. Although I used an exposure setting of 1/200 sec, the actual exposure is determined strictly by the duration of the flash pulse, which is much shorter than 1/200 sec. While flash pulse duration can be set manually (and I started out doing so), I now prefer to use E-TTL mode (Evaluative Through The Lens), which adjusts the flash duration automatically based on the amount of light that the camera senses coming through the lens from a short pre-flash at the aperture chosen. The more light that is sensed, the shorter the flash pulse – the less light sensed, the longer the pulse. Obviously, with a shorter flash pulse there is less likelihood that image sharpness will be affected by movement – either by the subject or by the camera-holder. Since light intensity decreases in proportion to distance, it is desirable to get the light source as close to the subject as possible to achieve the highest intensity and, thus, shortest flash duration.

It’s not that simple, however. Most insect macrophotographers agree that diffused light gives better results than undiffused light, but no matter what diffuser one uses there will be loss of light. Loss of light leads to longer flash pulse duration and, thus, increased potential for movement during the flash pulse (especially in hand-held photography). The trick, then, is to diffuse the light as much as possible, while at the same time minimizing light loss. I continue to favor my Puffer+Sto-Fen double diffuser for use with the 65mm lens, because it places the outer diffuser almost right on top of the subject for maximal apparent light size. This is not to say that improvements still are not possible – the open-side design likely results in some loss of light, and a thin inner diffuser film to replace the Sto-Fens would probably further reduce light loss and allow for even shorter flash pulses (and probably also allow a bit more battery life). I’ll get around to effecting these improvements someday, but in the meantime the current setup is working pretty well.

Compositionally, I like this last photo the best due to the placement of the subject within the frame (all photos are shown completely uncropped, although I’m not above doing so), its slight upward-looking pose, and the evenly-blurred light-green background. This was achieved by using my left hand to hold the leaf on which the spider was sitting and to also serve as a brace for resting the camera, which I held with the right hand. This minimizes wind-movement and fixes the distance between the subject and the lens (as long as the subject sits still!). By carefully twisting and turning the leaf as the spider moved upon it, I was able to turn the spider into the desired positions, and by paying attention to what was behind the spider I could compose a nicely colored blurred background. Understanding subject behavior was a tremendous advantage in this case, as it allowed me to predict and anticipate how the spider would move in response to my finger-prodding and leaf turning to get desirable poses. I tend to get my best compositions after I’ve worked the subject for awhile and taken several shots to learn its behavior and get it accustomed to my presences – this is reflected in the accompanying photos, which are posted in the order in which they were taken. Make no mistake – patience and practice are still required. However, it’s techniques such as these that can make the difference between good photographs and great ones!

Edit 3/30/11, 11:50am: My thanks to G. B. Edwards, Curator at the Florida State Collection of Arthropods, who just sent me the following message:

Hi Ted,
Nice photos.  Most likely it is a female “Euophrys” sutrix, which is not a Euophrys nor even a euophryine, but a freyine, so eventually will have another genus name. It is one of the larger species in the subfamily.

This species is called “aranhas papa-moscas” in southern Brazil, where it is a principal predator of fruit flies in peach orchards (Wikipedia).

Copyright © Ted C. MacRae 2011

BitB Does CoO

/ Ted C. MacRae / Leave a comment

STS 5 ('Mrs. Ples') | Australopithecus africanus - Sterkfontein, South Africa

Although my fondness for beetles is well known, I also have an inordinate fondness for systematics.  For this reason, Catalogue of Organisms by Christopher Taylor has long been high on my ‘must read’ list.  While there are no limits to the taxa – extant or extinct – that he writes about, one can be sure that whatever subject he picks, it will be comprehensively covered and richly referenced.  One of his more popular features is ‘Name the Bug’ (“bug” being any group of organisms, not just insects), where readers are invited to identify a featured organism and provide evidence to support their answer.  Points may be earned (and even usurped) in this free-for-all competition, with series winners eligible to request a post on the taxon of their choosing or write a guest post of their own.  As the most recent winner of this competition, I have chosen the latter and written a post called Origins – A Day in the Broom Room.  It’s about paleoanthropology, human evolution, and a personal experience with some of the field’s most iconic fossils.  I know these are subjects far outside my normal fare, but I hope you’ll take a look anyway and I thank Chris for letting me elbow my way onto his site for a while.  While you’re there, be sure check out the rest of the fine content on CoO – it might end up on your ‘must read’ list as well.



Copyright © Ted C. MacRae 2011

Bichos Argentinos #5 – Cyrtocoris egeris

/ Ted C. MacRae / 14 Comments

Cyrtocoris egeris | 15 km S Reconquista, Pcia. Santa Fe, Argentina

Despite its obvious membership in the order Hemiptera, I knew the insect featured in ID Challenge #7 would be a difficult subject to identify.  This bizarre bug is Cyrtocoris egeris, a member of the small pentatmoid family Cytocoridae (congratulations to HBG Dave, who was the only commenter to correctly identify not only the family, but the genus).  While their relationship to Pentatomidae (stink bugs) and Scutellaridae (shield-backed bugs) is obvious, hemipterist-great Carl Schaefer thinks these insects might actually be most closely related to the Cydnidae (burrowing bugs).  I encountered this individual a couple of weeks ago in a soybean field in Santa Fe Province, Argentina.  Now, I have to be honest here – I did not figure this one out on my own. Instead, I assumed it must be some bizarre member of the Pentatomidae or Scutellaridae, and it was only after my repeated searches in either of those two families failed to turn up anything promising did I throw up my hands and call for hired help. This time it was USDA Research Entomologist Don Thomas, a pentatomid specialist (and former co-alumnus at the University of Missouri) who responded to my query with a genus-level ID. Once I had that bit of information in hand I was able to locate the recent revision of the family (Packhauskas and Schaefer 1998) and identify the species.

Looks stink bugish enough in this head on view...

In addition to the expanded scutellum bearing a broad-based spine or hump, members of this exclusively Neotropical family are characterized by flattened expansions of the anterior part of the head, the covering of flattened scalelike setae, and a mediodistal tubercle on at least the foretibiae. Packauskas and Schaefer (1998) recognize only three genera and 11 species in the family, its members occurring from Argentina north through central Mexico.

...but there's some crazy stuff going on at the back end.

My ID as C. egeris is based on the very well-developed scutellar crest and my interpretation of the humeral projections not extending forward of the anterior angles next to the head. Packauskas and Schaefer (1998) recorded this wide-ranging species from Mexico to Argentina, with the southernmost specimens in extreme northeastern Argentina (Pcia. Missiones), but Schaefer et al. (2005) later recorded it from Reconquista – also on soybean. Cyrtocoris gibber is very similar to C. egeris and is also widespread from Costa Rica to Argentina (and also with the southernmost record in Pcia. Missiones, Argentina), but in that species the humeral expansions project forward nearly as far as the anterior angles of pronotum (strongly surpassing a line drawn through the bases of these angles).  Besides soybean for C. egeris, the only other host records I am aware of for any species in the family are by Costa Lima (1940), who reported C. gibbus on the branches of Mimosa scabrella (Leguminosae), and Schaeffer et al. (2005), who reported C. tigrinus on Sida rhombifolia (Malvaceae) (although nymphs could not be reared to adulthood on this plant).

REFERENCES:

Costa Lima, A. 1940. Insetos do Brasil. 2° Tomo, Capitulo XXII. Hemipteros. Escola Nacional do Agronomia, Rio de Janeiro.

Packauskas, R. J. and C. W. Schaefer. 1998.  Revision of the Cyrtocoridae (Hemiptera: Pentatomoidea).  Annals of the Entomological Society of America 91(4):363–386;

Schaefer, C. W., A. R. Panizzi and M. C. Coscarón. 2005.  New records of plants fed upon by the uncommon heteropterans Cyrtocoris egeris Packauskas & Schaefer and C. trigonus (Germar) (Hemiptera: Cyrtocoridae) in South America.  Neotropical Entomology 34(1):127-129.



ID Challenge #7

/ Ted C. MacRae / 12 Comments

I hadn’t planned on doing another ID Challenge so quickly after the previous one¹; however, this critter is just too cool to keep in my pocket any longer.  Order-level identification shouldn’t be too much of a challenge, but I’ll be impressed with anyone who drills down much deeper than that – 2 pts each for correct order-, family-, genus-, and species-level identifications.  What the heck – I’ll go ahead and throw in superfamily as a points-earner as well.  Supporting information for your IDs will help your cause, and we all know my predilection for handing out bonus points on the most subjective of bases.  As always, standard ID Challenge rules apply.

¹ For those of you wondering about the recent flurry of posts, I’m on a well-earned vacation right now and have pledged to fritter away as much time on idle pursuits as possible rather than fret about accomplishing anything constructive.

Copyright © Ted C. MacRae 2011

A thrips is a thrips…

/ Ted C. MacRae / 7 Comments

Caliothrips phaseoli (bean thrips) - adults | Fontezuela, Pcia. Buenos Aires, Argentina

The critter in ID Challenge #6 is, as most surmised, a thrips¹, and although the black-and-white banding of the elytra make the predaceous “banded thrips” (Aeolothrips sp. of the family Aeolothripidae) a logical ID choice, the species in the photograph is actually the phytophagous “bean thrips” (Caliothrips phaseoli of the family Thripidae).  The individuals in that photo and the additional photos shown here were encountered in several soybean fields during my visit to Argentina last week.  The species seems to be having a bit of a population surge on soybeans in the Humid Pampas – Argentina’s main soybean growing region – due to the dry conditions they’ve had as of late.  Their short life cycle (egg to egg in 2 weeks) and preference for generally protected lower leaf surfaces, along with the lack of any registered chemical insecticides labeled for their use on soybean, makes control of this insects especially problematic.

¹ Yes, that’s “a thrips” – not “a thrip” (similar to deer, species, sheep, etc.).  Personally, I’ve always had trouble with singular use of this definitely plural-looking word – it must be the “s” at the end and the completely natural sound of the word “thrip” in singular use.  Then again, one “specie” doesn’t sound right, so who knows?  At any rate, I’ve managed to force myself to say “a thrips” (although I still wince a little bit inside whenever I do).

Caliothrips phaseoli (bean thrips) - nymphs | Oliveros, Pcia. Santa Fe, Argentina

Thrips are tiny – the adults in the above photo (only slightly cropped) measure no more than ~1 mm in length, testing the limits even of my MP-E 65mm 1-5X macro lens at full magnification.  There are some interesting features about the morphology and life history of thrips – namely their “rasping-sucking” mouthparts and life history that seems somewhat intermediate between the incomplete metamorphosis exhibited by other exopterygote insects (egg, nymph, adult) and the complete metamorphosis of the endopterygotes (egg, larva, pupa, adult).  Thrips actually have only a single mandible (the other aborting development during embryogenesis), which they use to “rasp” a hole into the plant tissues upon which they feed.  The remaining mouthparts then form a sort of siphon, that is used to imbibe the liquids that accumulate within the hole.  This seems to represent – at least functionally – an intermediate step in the evolution of the true piercing/sucking mouthparts exhibited by other hemipteroid insects.  Life history-wise, only the first- and second-instar nymphs (2nd photo above) feed, the third- and fourth-instars becoming quiescent stages termed the propupa and the pupa, respectively.

Reader question: I presume the shiny, black globs on the hairs of the plant are fecal deposits, but why are they placed as such? Does it help avoid spoilage of the leaf feeding surface – I’m not aware of any other insects that are so fastidious (except perhaps ants). Maybe there is a defensive function? I’ve searched and found nothing about this, so please let me know if you have any insight.

There seems to be some difference of opinion regarding the actual species name for these insects.  Most applied economic literature dealing with thrips in soybeans calls these Caliothrips phaseoli – a widespread species occurring in North, Central, and South America.  However, a number of references (both economic and taxonomic) recognize South American populations as a distinct species, C. brasiliensis (or C. braziliensis, depending on the source), based on the solid dark rather than medially lightened elytral band.  I also found some references that seem to regard C. phaseoli as s a synonym of C. fasciatus (although this comparison at Pests and Diseases Image Library seems to show distinct differences in abdominal sculpturing between the two species).  I’m going with C. phaseoli over C. brasiliensis based on a checklist of Brazil Thysanoptera (Monteiro 2001) and the Argentina checklist at the World Thysanoptera website, and the general lack of mention of C. fasciatus as a pest of soybean in Argentina in the literature also makes me go with C. phaseoli.  Congratulations to Ben Coulter, who wins this challenge with a clean sweep of the ID and host plant, and to HBG Dave, whose 4 pts moves him into the lead in the current BitB Challenge session.
 
REFERENCE:

Monteiro RC. 2001. The Thysanoptera fauna of Brazil. Pp. 325–340 in Marullo, R. & Mound, L.A. (eds) Thrips and Tospoviruses: Proceedings of the 7th International Symposium on Thysanoptera. Australian National Insect Collection, Canberra.

Copyright © Ted C. MacRae 2011

ID Challenge #6

/ Ted C. MacRae / 18 Comments

It’s been awhile since our last ID Challenge.  I’ll give 2 pts each for correctly naming the order, family, genus, and species and whatever supporting information you can provide.  Bonus points if you can surmise host plant, location, etc.  Standard ID Challenge rules apply.  No trick questions this time – it’s just about the bug!

Copyright © Ted C. MacRae 2011

Brazil Bugs #16 – Outro Percevejo

/ Ted C. MacRae / 6 Comments

Proxys sp. | Barão Geraldo, Campinas, Brazil

Another stink bug (family Pentatomidae) from my recent travels to South America, but this one from southeastern Brazil rather than Argentina.  Although the white spot at the apex of the scutellum is a common theme across the family, the jet black coloration and strongly acute clypeus (“nose”) immediately reminded me of Proxys punctulatus from eastern North America. Although that species does also occur south through Mexico and Central America into northern South America, the lack of distinctively black femoral apices (“knees”) on this individual suggest it is likely a different species.  I’ve not found much information on other species in this genus, as my old standby Flickr repeatedly proffers images of P. punctulatus in its Pentatomidae pages but not other species in the genus.  Grazla and Campos (2010) list P. hastator from “Cayenna” (likely French Guiana) and P. victor from “Brésil,” and an illustration of the latter in the monumental Biologia Centrali-Americana (Distant 1880-1893) agrees reasonably well (but not completely) with this individual.  For now, this will have to stand as Proxys sp.

REFERENCES:

Distant, W. L.  1880-1893.  Biologica Centrali-Americana. Insecta. Rhynchota. Hemiptera-Heteroptera. Volume I.  London: published for the editors by R. H. Porter, 462 pp.

Grazia, J. and L. A. Campos. 2010. Neotropical Pentatomidae (Insecta: Hemiptera: Heteroptera) of the collection of Massimiliano Spinola preserved in the “Museo Regionale de Scienze Naturali”, Turin, Italy. ZOOLOGIA 27(3):413–424.

Copyright © Ted C. MacRae 2011