nature

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

Bichos Argentinos #4 – Balancing Act

/ Ted C. MacRae / 4 Comments

Nezara viridula (southern green stink bug) | Pergamino, Pcia. Buenos Aires, Argentina

I encountered this adult Nezara viridula (southern green stink bug) (Hemiptera: Pentatomidae) in a soybean field in Buenos Aires Province, Argentina.  I liked the way it balanced itself on the leaf on which it was sitting to keep its body level.

Copyright © Ted C. MacRae 2011

Bichos Argentinos #3 – “Bicho Torito”

/ Ted C. MacRae / 16 Comments

Diloboderus abderus, male | Buenos Aires, Argentina

In her appeal for submissions for her upcoming issue of An Inordinate Fondness, Susannah lamented the paucity of beetles in the closing weeks of her northern winter and mentioned in passing that even I had gone more than a week without posting about this great order.  I hadn’t realized that myself, so here I present Diloboderus abderus, one of the beetles that I encountered during my visit last weekend to La Reserva Ecológica Costanera Sur in Buenos Aires, Argentina.  This species, known commonly in Argentina as bicho torito (“little bull bug”) is common enough in Argentina and southern Brazil, where its white grub larvae have become somewhat of a pest in lawns, pastures, and grass crops such as wheat by way of feeding on the roots.  I first encountered this species during one of my previous trips to Argentina, where during a rain storm I saw literally hundreds of adults emerging from mowed grass medians in the city streets of Pergamino.  These photographs show two of numerous dead individuals that I found laying on the ground of similar medians just outside the reserve.  As with many scarab beetles in the subfamily Dynastinae (containing also the recently featured Dynastes tityus), males (above) are armed with pronotal and cephalic horns – presumably for use in sexual combat – while females (below) are unarmed.

Diloboderus abderus, female | Buenos Aires, Argentina

Copyright © Ted C. MacRae 2011

Bichos Argentinos #2 – Pseudomyrmex sp.

/ Ted C. MacRae / 12 Comments

Pseudomyrmex sp. (twig ant) | Reserva Ecológica Costanera Sur, Buenos Aires, Argentina

One of the insects I tracked at La Reserva Ecológica Costanera Sur in Buenos Aires, Argentina last weekend was this twig ant in the genus Pseudomyrmex.  I had noticed these slender, wasp-like ants previously on trips to the U.S. desert southwest, but it wasn’t until I read a couple of recent posts about them at Myrmecos and 6legs2many that I knew specifically what they were. 

Alex characterizes these ants as “delightfully gentle, quirky little insects.”  What he didn’t mention is how frenetic and unceasing they are as they forage amongst the shrubbery.  I must have taken a couple dozen shots of several individuals over the course of the day, deleting every single one on the spot because I couldn’t get a clear, close, focused, nicely composed, unobstructed image.  Their habit of crawling rapidly along slender twigs is problematic enough, with little opportunity to brace the camera against anything steady and spend time composing the shot.  Add to that the frequently thorny nature of the trees they were roaming and their annoying habit of darting around to the backside of whatever twig they were on whilst trying to follow them in the viewfinder, and I almost decided I’d met my match and could do without the shot.  In the latter part of the day I encountered this individual, and as I already had my 65mm lens mounted I decided to give it another try.  I can’t say that I actually figured out the secret to getting the shot, but rather that I just lucked out and happened to have hit the shutter release at just the right moment – and with reasonable focus – as I tracked the ant along the branch on which it was crawling.  It was the only shot of one of these ants that stayed on the card that day.

The genus is huge, with 209 species occurring primarily throughout the Neotropics.  As a result, it would be foolish for me to even attempt a species ID.  Still, I can’t help noticing its great resemblance to this photo of Pseudomyrmex phyllophilus, taken by Alex in – you guessed it, Buenos Aires, Argentina.  I’ll wait for the correction, but in the off-chance that I’m right I think I deserve points on somebody’s scorecard!

Copyright © Ted C. MacRae 2011

Bichos Argentinos #1 – Eristalinus taeniops

/ Ted C. MacRae / 2 Comments

Eristalinus taeniops - a hover fly in the family Syrphidae

It figures that perhaps the most striking insect I saw at La Reserva Ecológica Costanera Sur in Buenos Aires, Argentina would be an introduced species, as the area itself is a man-made reconstruction of the wet Pampas grasslands endemic to coastal areas of the Rio de la Plata.  My identification of this fly as Eristalinus taeniops is based on its great resemblance to the many online photographs that exist from both South America and the U.S. and also the Old World where it is apparently native.  I found no more authoritative sources with which to confirm the ID, so this online comparative will have to do (muscophiles feel free to comment or correct). 

According to BugGuide, E. taeniops is a recent import to the U.S. from Africa, and in fact it has apparently successfully invaded much of the world.  I suppose most folks will be inclined to forgive the fly for all this because of its strikingly patterned eyes, which I would have dearly loved to have gotten in tight for a closeup.  This shot with the 100mm lens dialed in to the max (and only slightly cropped for composition), however, was the only one I managed – the fly bolted as I quickly tried to switch to the 65mm lens, and although I saw two more individuals afterwards, I couldn’t get anywhere close to them in the day’s heat.  Eyes notwithstanding, the species is a near perfect mimic of a honey bee, making one wonder what selective pressures drove the development of these fantastically contrasting eyes.

Copyright © Ted C. MacRae 2011

North America’s largest scarab beetle

/ Ted C. MacRae / 28 Comments

Dynastes tityus male - USA: Missouri, Jefferson Co., DeSoto

As one of North America’s largest, most written about, and most photographed beetles, Dynastes tityus (eastern Hercules beetle) hardly needs an introduction.  I photographed this male specimen from my collection back in December while testing my DIY diffuser for the MT-24EX twin flash and 100mm macro lens.  It’s a good test subject for such – its glossy exoskeleton may be beauty to the eye but is the bane of flash photographers, and its nearly 60mm of length demand a huge subject-to-lens distance that gives even the largest lens-mounted flash a small apparent size.  Nevertheless, the diffuser did a pretty good job of creating even illumination and preventing harsh specular highlights, giving almost the effect of an indirect strobe in a white box.

Dense setae adorn the underside of the thoracic horn of the male.

I hadn’t really noticed until I took the photos the dense adornment of setae (hairs) on the underside of the thoracic horn.  While setae in insects most often perform a tactile function, the density and placement on the horns of the males of these beetles makes me wonder if they might serve more of a display function.

Despite the overwhelming popularity of this beetle amongst hobbyist breeders and its widespread occurrence across the eastern United States (and the internet), it is not one that I have encountered with much frequency myself.  I suspect this is due to the position of Missouri near its western limit of distribution – likely a function of the species’ preference for moist treehole cavities with rotting wood in which the larvae can develop.  This particular specimen was given to me many years ago by a nursery grower in Jefferson Co. during my first job out of graduate school – before I’d ever found one myself, but since then I’ve encountered perhaps half a dozen or so at blacklights in mesic forests across the eastern Ozark Highlands.  Most recently (last summer) I found a female sitting on my driveway, apparently attracted to the mercury vapor lamp above the garage that I leave on occasionally during the months of June and July just for such purpose.

Copyright © Ted C. MacRae 2011