CRAMBIDAE  -  Diatraea considerata Heinrich

Larval diagnosis (Detailed)

The larva of Diatraea considerata was recently surveyed in Mexico by Rodriguez del Bosque (2009, 2012). Because of confusion with Diatraea magnifactella, literature and preserved specimens said to be D. considerata cannot always be trusted. For the purposes of this project, we limit literature citations on D. considerata to publications by Box (1935), Bleszynski (1969), Solis (2004), and Rodriguez del Bosque (2009, 2012, or works coauthored with him). Our material examined will require some comments and justification.

Reference specimens of D. considerata were loaned from the Box collection at the United States National Museum. These (8 larvae, 2 pupae) were collected in Sinaloa during 1933 by T. Vogliotti and reared from sugarcane (see Box 1935). This is the type locality for D. considerata and outside the known range of D. magnifactella. Two larvae, one molting, labeled as D. considerata, were collected during May, 1984 at Tepic (Nayarit, Mexico) by Browning, Bennett and Melton. This is also outside the known range of D. magnifactella. Although the label does not state these larvae were from sugarcane, all three collectors have studied natural enemies of sugarcane stem borers in western Mexico (Melton et al. 1986, Bennett, 1969). It seems reasonable to assume the host was sugarcane.

Reference specimens (8 larvae) of D. magnifactella were also borrowed from the Box collection. These were from Tamaulipas, collected on sugarcane in 1951 by Box. At that time, Diatraea magnifactella was known to be a dominant borer in the region (Rodriguez del Bosque et al. 2011). We obtained additional well preserved fresh specimens of D. magnifactella from sugarcane stems at Morelos, Mexico (outside the known range of D. considerata) in 2011 identified and sent by L. A. Rodriguez del Bosque.

Another issue is how to separate D. considerata from both D. grandiosella and D. saccharalis. Our specimens of D. grandiosella are from the United States (Texas A&M laboratory culture, Kansas, Arizona) which is outside the range of D. considerata. Numerous D. saccharalis were examined, mostly from Honduras (see Passoa 1985) and Mexico (from a USDA rearing project, see Riley and Solis 2005). These were often associated with reared adults or were taken from areas with few other sibling species. A small series of intercepted Diatraea specimens from sugarcane, without specific Mexican localities, were examined from California and Texas ports.

The most accurate identification of D. considerata requires a combination of factors including origin, host, appearance, and morphology. Each of these will be discussed in turn.

Box (1935), Bleszynski (1969), Solis (2004), and Rodriguez del Bosque (2009, 2012) all record D. considerata from Mexico on sugarcane. For now, it seems best to restrict the distribution to Mexico and the host to sugarcane. The Mexican distribution is from Sinaloa south to Michoacan. Any other record will require confirmation. Particularly important, and doubtful, is the record for D. considerata from Texas (Zhang 1994: 182). We could not verify any records of D. considerata from Venezuela as suggested by Sugar Research Australia (not dated).

Characters for recognizing the genus Diatraea, mentioned under D. lineolata, will also apply to D. considerata. In particular, there is an inner tooth on the mandible (not obvious on our photo); both the L and SV setae lie anterior to the prothoracic spiracle; the prespiracular pinaculum extends below the prothoracic spiracle but not behind it; the SV group is bisetose on the thoracic segments; and the crochets of A3-6 are in a triordinal circle. The non-diapausing form has an obvious elongate extra pinacula lacking setae on the mesothorax and metathorax (Passoa 1985, Weisman 1986).

Based on Box (1935) and our preserved larvae, Diatraea considerata has a light orange to honey colored head and a honey colored prothoracic shield. Small larva (16 mm or less) have lateral stripes but older larvae (up to 33 mm long) tend to be transversely marked. These markings, if present, are lavander to light purple to pink. The anal shield is pigmented. This coloration is similar to D. magnifactella but different from D. saccharalis or D. grandiosella. The head color of D. saccharalis tends to be reddish brown, more rarely light brown or honey colored. It is also smaller (25 mm long or less) than D. considerata. The coloration of D. grandiosella is more like D. considerata and D. magnifactella but without transverse bands or the lavander to purple to pink markings. In summary, large larvae (25 mm or more), without a red to brown head, but with transverse bands or at least spots that group in a transverse marking, are either D. considerata or D. magnifactella if from Mexican sugarcane. Separation of these two species is based on morphology, not host.

Diatraea magnifactella has a minute SD2 seta below the middle of the SD1 pinaculum on A8. When SD2 on A8 is visible in D. considerata, it is located somewhere anterior to the midline of the SD1 pinaculum. Other morphological characters of importance shared by both species include an inner tooth on the mandible and a sclerotized patch of tonofibrillary platelets is anterior to the prothoracic coxae. Four commonly intercepted Diatraea we examined (lineolata, saccharalis, magnifactella, and considerata) all have A9 with the D2 setae joined on a common pinaculum above a second pinaculum with D1 above the hairlike SD1 seta. The spinneret of Diatraea appears to have microsetae at the tip but the distribution of this character is unknown.

The frontal pores are well below a line connecting the F1 setae in most D. grandiosella. In addition, the SD1 pinacula extends to middle of the spiracle on A3-6 and the paraproctal setae are only half as long as SV1 on A9. This easily separates D. grandiosella from D. considerata.

Two keys to Diatraea are presented below. One emphasizes morphology without mentioning origins and includes only the most common Mexican species. If a specific origin in Mexico or a country in Latin America is known, the second key can be used. It is more accurate and includes some of the rarer species. Each has its own set of warnings and caveats not repeated here. A larger series of determined specimens is needed to determine the variation of taxonomic important characters.

Identification authority (Detailed)

Identification of D. considerata is only justified in a few cases; otherwise it is more accurate to stop at the genus level. At minimum, the origin must be from the proper part of Mexico on sugarcane. SD2 must be anterior to the midline of the SD1 pinaculum on A8 or be apparently absent. Late instar larvae should have transverse bands; smaller larvae are striped laterally. Some specimens will no doubt fit the above characterization, others will not. Origin and host is more important than morphology until a large seris of specimens are studied.

As with D. lineolata, origin and host information are critical for accurate identification of D. considerata. Inspectors must get specific origins from Mexico, photograph the larva or remember details of the head and body color before preservation. Ports must be prepared to send occasional specimens to quarantine facilities for rearing to the adult stage. This is especially important because several species of Diatraea have unknown life histories. Because we did not study the diapausing forms carefully, use caution with identifications of these stages.

Morphological guide to known species of Diatraea intercepted at U.S. ports of entry from Mexico

Guide to species of Diatraea intercepted or potentially encountered at U.S. ports of entry using morphology and origin

CRAMBIDAE  -  Diatraea considerata Heinrich

Origin records

Diatraea considerata has been intercepted from the following locations:

Bolivia, Mexico, Nigeria, Peru

Records from outside of Mexico likely represent misidentifications.

Host records

Diatraea considerata has been intercepted on the following hosts:

Cuminum cyminum, Cymbopogon citratus, Physalis sp., Saccharum officinarum, Saccharum sp., Saccharum spontaneum, Zea mays, Zea sp.

Records from hosts other than Saccharum likely represent other species of Diatraea or Pyraloidea (on Cuminum cyminum, Physalis).

CRAMBIDAE  -  Diatraea considerata Heinrich

Setal map

Diatraea considerata setal map

Click here to download a full-size printable PDF of this larval setal map