true bugs

Stink Bugs on Soybean in Argentina

/ Ted C. MacRae / 17 Comments

Despite the natural history and taxonomic focus on beetles and other insects I have adopted for this blog, I am by day an agricultural research entomologist.  For the past 15 years soybean entomology has been my focus, and there is no better nexus for soybeans and entomology than South America.  Cultivated hectares have increased dramatically in Argentina and Brazil over the past several decades, now totaling nearly 80 million acres in those two countries alone (roughly the same area as in the US, by far the world’s largest producer of soybean).  Unlike the US, however, where insect pressure is minor outside of a small number of acres in the southeast, significant pressure occurs in nearly 100% of South America’s soybean acres.  Lepidopterans, primarily species in the family Noctuidae such as velvetbean caterpillar (Anticarsia gemmatalis) and soybean looper (Pseudoplusia includens), are the most important pests, followed closely by stink bugs.  This latter group is especially problematic for growers to deal with.  Stink bugs feed on the developing seeds, causing direct yield impacts through reductions in weight and quality, and because they are a guild of insects rather than a single species, differences in product efficacy against the different species can lead to ineffective or inconsistent control.  I’m involved in trying to do something about this, and while I hate to be deliberately coy, suffice it to say that there is an awful lot of insecticide being sprayed on an awful lot of acres and that the world really would be better off if this weren’t the case.

During my recent visit to Argentina this past March, I took advantage of the opportunity while touring soybeanland to photograph a number of these stink bug species.  Proper identification of stink bugs in a crop is the first step towards controlling them, thus I present here my own photographic guide to some of the more important stink bug species found on soybean in Argentina.

Nezara viridula (chinche verde), adult | Pergamino, Argentina

Nezara viridula, 5th instar nymph | San Pedro, Argentina

Nezara viridula, 1st instar nymphs on egg mass | Oliveros, Argentina

Piezodorus guildinii (chinche de las leguminosas), adult | Pergamino, Argentina

Piezodorus guildinii, 1st instar nymphs on egg mass | Acevedo, Argentina

Edessa meditabunda (alquiche chico), adult | Acevedo, Argentina

Edessa meditabunda, 1st instar nymphs on egg mass | San Pedro, Argentina

Edessa meditabunda, eggs nearing eclosion (note eye spots) | Oliveros, Argentina

Euschistus heros (chinche marrón), adult | Oliveros, Argentina

Dichelops furcatus (chinche de los cuernos - note two ''horns'' in front), adult | Inés Indart, Argentina

Copyright © Ted C. MacRae 2011

Bichos Argentinos #12 – Lace Bugs

/ Ted C. MacRae / 9 Comments

Corythaica cyathicollis on upper leaf surface of Solanum granuloso-leprosum.

Shortly after entering La Reserva Ecológica Costanera Sur (Buenos Aires, Argentina) during my early March visit, I noticed a fairly large patch of solanaceous-looking shrubs.  Even from a distance, I could see patterns of white stippling on the foliage immediately identifiable as signs of lace bugs, true bugs (order Hemiptera) in the family Tingidae.  As the only arborescent solanaceous plant recorded from the reserve, I was quickly able to identify the plant as Solanum granuloso-leprosum (Haene and Aparicio 2007), but I expected an identification of the bug to be much more difficult to come by.  Afterall, 84 species of tingids distributed in 25 genera have been recorded from Argentina (Montemayor and Cascarón 2005), and lace bug photos aren’t very frequently encountered in the variety of web sites that I visit when trying to get a lead on the identity of insects outside my area of expertise.

Corythaica cyathicollis adult. The black spots either represent frass or protective egg coverings.

Still, I had a clue—the association of the species with Solanum. Lace bugs are predominantly specialist feeders, with many species showing fidelity to a particular plant genus or group of related genera. The genus Solanum contains a number of economically important species, thus, it was a good bet that this species has at some point been considered an economic pest. With this in mind, I opened my volume of Heteroptera of Economic Importance (Schaefer and Panizzi 2000) to the chapter on lace bugs (Neal and Schaefer 2000) and began looking through the species accounts for South American species recorded on Solanum or other species in the family Solanaceae. I only had to reach the second species account before finding Corythaica cyathicollis and the statement “This Neotropical species is a pest on many solanaceous crops…” The identification was confirmed when I found a rather complete description of the species’ systematics, biology, and economic importance (Kogan 1960), complete with line drawings of the adults and all immature stages. Comparison of my photos with these drawings leaves little doubt that this is, indeed, C. cyathicollis.  (Interestingly, Montemayor and Cascarón (2005) list 28 species of Solanum as recorded hosts for C. cyathicollis in their Argentina checklist; however, S. granuloso-leprosum is not among them…)

Corythaica cyathicollis late-instar nymphs.

The bristles of needle-like setae exhibited by the nymphs may be useful for species identification by entomologists (and even phylogenetic analyses—see Guilbert 2005), but for the nymphs themselves it seems fairly obvious that they serve some adaptive function for protection. Neal and Schaefer (2000) note that nymphs of many species of Tingidae seem to be protected by a wide variety of other adaptive mechanisms as well, including maternal care, the production of alarm pheromones and possibly the secretion of noxious compounds. Indeed, most tingids occur in multiple aggregations with large numbers of nymphs of the same species on a single host plant relatively free of predation and parasitism—it is difficult to imagine that such aggregations could exist without employing a strong arsenal of multiple defense mechanisms.

A presumably teneral adult Corythaica cyathicollis.

Occasional adults were seen within the aggregations that showed decidedly lighter coloration than the majority of adults seen. The aggregations were comprised primarily of adults and late-instar nymphs, so I presume these light-colored adults represented newly molted, teneral individuals that will eventually assume normal coloration once their new adult exoskeleton fully hardens.

Adult Gargaphia lunulata on lower leaf surface of Ricinus communis.

Later in the day, I encountered a different lace bug species on a different shrub—Ricinus communis.  This is the famous castor oil plant, a member of the Euphorbiaceae, native to the Old World and now widely distributed throughout tropical regions.  Despite castor oil’s reputed ability to heal wounds and cure ailments, the beans and other plant parts also contain ricin—a toxin with known insecticidal properties.  Apparently these lace bugs possess some mechanism that makes them immune from its effects.

Gargaphia lunulata 5th instar nymphs (and an apparent 1st instar in lower left corner).

This species was also fairly easy to identify—one of the species listed in Neal and Schaefer (2000) as feeding on Ricinus is Gargaphia lunulata, which they note feeds on several useful South American plants belonging to a number of families, including the Euphorbiaceae.  Photographs and drawings of this species can be found in Ajmat et al. (2003) and agree well with the adults and nymphs I found on this plant.  Unlike C. cyathicollis, which were found on the adaxial (upper) surface of the leaves, I found G. lunulata exclusively on the abaxial (lower) surfaces.  Nevertheless, the characteristic white stippling was easily visible on the leaves and gave immediate clue to their presence.

Photo Details: Canon 50D w/ MP-E 65mm 1-5X macro lens (ISO 100, 1/200 sec, f/13), Canon MT-24EX flash w/ Sto-Fen + GFPuffer diffusers. Typical post-processing (levels, minor cropping, unsharp mask). Photo 1 taken at 1X, photos 2 through 6 taken at or near 5X.

REFERENCES:

Ajmat, M. V., S. G. Bado, M. A. Coviella and M. J. Pannuzio. 2003. Aspectos morfológicos, biológicos y daño de Gargaphia lunulata (Mayr) 1865 (Heteroptera: Tingidae) sobre Passiflora caerulea L. (Passifloraceae). Boletin Sanidad Vegetal Plagas 29:339–346.

Guilbert, É. 2005. Morphology and evolution of larval outgrowths of Tingidae (Insecta, Heteroptera), with description of new larvae. Zoosystema27(1):95–113.

Haene, E. and G. Aparicio.  2007.  100 Trees of Argentina. Editorial Albatros, Buenos Aires, República Argentina, 128 pp.

Kogan, M.  1960.  Corythaica cyathicollis (Costa, 1864), aspectos sistemáticos, biológicos e econômicos (Hemiptera, Tingidae). Memorias Instituto Oswaldo Cruz 58(1):59–88.

Montemayor, S. and M. del Carmen Coscarón. 2005. List of Argentinian Tingidae Laporte (Heteroptera) with their host plants. Zootaxa 1065:29–50.

Neal, J. W., Jr. and C. W. Schaefer. 2000. Chapter 4. Lace Bugs (Tingidae), pp. 85–137. In:C. W. Schaefer and A. R. Panizzi (Eds.). Heteroptera of Economic Importance, CRC Press LLC, Boca Raton, 828 pp.

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.



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

Brazil Bugs #4 – Mais dos percevejos

/ Ted C. MacRae / 24 Comments

I found mais dos percevejos (more of the leaf-footed bugs) on the still-unnamed pink flowering shrub in back of the hotel in Campinas, Brazil.  Not only am I convinced that they truly do belong to the family Coreidae (for the reasons mentioned in the earlier post and below), but also that despite the different color patterns shown by the two individuals in that post that they are indeed a single species.  I also found the above individual, representing an even more heavily melanized version than the two shown previously.  In looking at a large number of individuals on the shrubs (and subsequently encountering them in a different part of Campinas over the weekend), it became clear that there were not just two distinct color forms but a broad range of variability.  I could believe maybe two species occurring together on a common resource, but it seems unlikely that each color variation represents a different species.  Thus, it now seems that there is one highly variable species visiting these flowers.

I had an idea on how to find the name of this species that almost worked.  Rather than Googling “leaf-footed bug” or “Coreidae,” I tried “percevejo” instead, along with Brazil or Brasil.  There were 3 or 4 photographs that showed up in the images search that I recognized instantly as belonging to the same species.  Unfortunately, none of the links where the photos were found gave any information more specific than family (all, however, agreeing with family Coreidae).  I think it’s time to send an email to Harry Brailovsky, a coreid specialist at the Instituto de Biologia (UNAM) in Mexico City.

Photo 1: Canon MP-E 65mm 1-5X macro lens (ISO 100, 1/200 sec, f/13).
Photo 2: Canon 100mm macro lens (ISO 100, 1/200 sec, f/16).
Both photos: Canon 50D, Canon MT-24EX flash w/ oversized DIY concave diffuser. Typical post-processing (levels, color, unsharp mask).

Last minute edit: I just heard back from Harry Brailovsky as I was ready to post (thank you Harry!).  The insect is, indeed, a species of Coreidae, which he identified as a member of the genus Hypselonotus.  I did some searching online to see if I could find any additional clues as the species identity – I found no images that looked right but did find this key to the Hypselonotus of Costa Rica.  The key relies on some ventral characters, and I’m a little uneasy about using it for something from southern Brazil, so I think I’ll just wait until Harry has a chance to look it up when he returns to the museum.

Second update 1/26/11:  Harry has confirmed the species as Hypselonotus interruptus, which was mentioned but not included in the key that I linked to above.  The only online images I have found of this species are at this link. Either Harry is wrong (unlikely), the photos in the link are misidentified (maybe), or the species is enormously variable (perhaps quite likely).

Copyright © Ted C. MacRae 2011

A “leafless” leaf-footed bug

/ Ted C. MacRae / 20 Comments

Merocoris distinctus feeding on flower stem of Coreopsis lanceolata.

This is Merocoris distinctus, a true bug in the family Coreidae whose members are usually recognized by their distinctive flattened hind tibiae (and hence the common name, leaf-footed bugs). This diminutive species, however, lacks that character, instead sporting strangely curved hind tibiae along with club-shaped (incrassate) hind femora. It’s a chunky little species – much smaller than the typical leaf-footed bugs seen across North America, and is most often encountered in grassland habitats where it feeds on herbaceous plants such as goldenrod, Solidago spp. (Slater and Baranowski 1978). This individual was seen probing the upper flower stem of lanceleaf tickseed, Coreopsis lanceolata, during May of last year at Shaw Nature Reserve in east-central Missouri. I’m not sure how well the life history of this species is understood, but I did find one interesting record of twelve individuals feeding gregariously on a dead chicken (Engelhardt 1912)! Apparently, feeding on carrion and other extra-phytophagous foods such as bird droppings and dung is a not uncommon practice among the Coreidae and closely related Alydidae (Adler and Wheeler 1984).

I kind of lucked out with this shot – I’d just gotten my new camera two weeks earlier and can’t say I really knew what I was doing at this point. I had first noticed and photographed the bug sitting on top of the flower but totally blew the exposure due to the flower’s bright yellow color.  My clumsy approach also caused the insect to move under the flower, where I watched it settle down and begin feeding before trying another shot. The dorsal surface of this species is mottled gray and brown, allowing the bug to blend in with most backgrounds. The underside of the body, however, is thickly matted with white hair, providing a very nice contrast with the black background that I stumbled upon achieved in this photo to emphasize the distinctive appearance of this often-overlooked insect.

Photo Details: Canon 50D w/ 100mm macro lens (ISO 100, 1/250 sec, f/14), Canon MT-24EX flash (1/4 ratio), undiffused. Typical post-processing (levels, minor cropping, unsharp mask).

REFERENCES:

Adler, P. H. and A. G. Wheeler.  1984. Extra-phytophagous food sources of Hemiptera Heteroptera: Bird droppings, dung, and carrion.  Journal of the Kansas Entomological Society 57(1):21-27.

Engelhardt, G. P. 1912. A hemipteron on carrion.  Journalof the New York Entomological Society 20:294.

Slater, J. A. and R. M. Baranowski. 1978. How to Know the True Bugs. W. C. Brown Company Publishers, 256 pp.

Copyright © Ted C. MacRae 2010