Cockroaches

Blattodea (= Blattaria). Spanish: Cucarachas. Portuguese: Baratas. Quechua: Utiuti.

Cockroaches are regarded with disgust by nearly everyone. Although widely believed to carry disease, their importance as mechanical vectors is probably overrated

(Roth and Willis 1957). Some evidence to the contrary does exist (Gazivoda and Fish 1985). It is a shame that a few unsavory types have given a bad name to an otherwise diverse and biologically fascinating group of insects, one begging investigation in Latin America where a large and distinctive fauna exists which is practically unknown.

Cockroaches are among the most primitive and ancient of winged insects. Their origin dates back 250 million years to the Carboniferous period. Fossil records show that they were very abundant at that time and very little different in structure from their modern descendants.

Nocturnal cockroaches are mostly oval, much flattened and dull-colored, with pliable wings, all adaptations for life in dark, confined spaces. Others are teardrop shaped, convex, with brightly hued, hard, beetlelike wings; these features relating them to an exposed, diurnal existence on vegetation, tree bark, and tree trunks.

All cockroaches have a well-developed, thin layer of grease or wax on the outside of the cuticle which protects them from desiccation and gives them their slick feel. The head is horizontal but bent backward so that the mouthparts project toward the rear, being situated almost between the bases of the front legs. The head is often entirely concealed from above by a large, widely expanded, and flattened disklike shield (the pronotum), out from under which project the very long, whiplike antennae. Wings are usually present and large with a highly complex, reticulate venation. They are often abbreviated in the female and in many species may be absent altogether from both sexes. The fore wing is narrow and elongate and more rigid in texture than the hind wing, which is broad, fanlike, and membranous. The legs are well spined. A pair of elongate, segmented cerci project from the apex of the abdomen. These appendages are richly endowed with external sense organs adapted for perception of vibrations, sound, and air movements.

Female cockroaches give birth in different ways. They normally encapsulate their eggs in groups of few to many within a hard, darkly pigmented case (ootheca), which is deposited in the proper environment. Some retain the case in the birth canal where it often remains partly extruded until the young hatch. Others keep it entirely within the abdomen, and the nymphs hatch inside the mother, spending up to several days in a kind of uterus before being born alive.

Cockroaches actively secrete a variety of exocrine substances, such as sex lures, aggregation stimulants, and defensive compounds of all kinds (Roth and Alsop 1978). The glands that produce these chemicals are located either in the head (mandibular glands) or on the abdomen, usually on the back of the more posterior segments.

A great deal is known about the anatomy, physiology, and natural history of the few common domestic and semidomestic forms (Cornwell 1968, Guthrie and Tin-dall 1968), but information is scarce concerning these aspects in the majority of wild species. One study (Schal and Bell 1986) indicates a vertical segregation of species in the layered vegetation of forests. Many genera are represented in bromeliad "terraria" (Rocha and Lopes 1976); Epi-lampra (fig. 5.8a) has been observed to swim well (Crowell 1946), even having tubular spiracles at the rear of the abdomen, possibly functioning as elementary snorkels. Several species mimic other insects. For example, lycid beetles of the genus Calopteron are mimicked by the cockroaches Holocampsa and Paratropes, lampy-rid beetles Cratomorphus and Aspisoma by Achroblatta luteola (figs. 5.8b, 5.8c), and the giant fungus beetle Erotylus by Plectoptera. Most of these are diurnal and commonly seen running on forest understory vegetation; the firefly mimics are nocturnally active like their models, the similarity be

Figure 5.8 COCKROACHES, (a) Aquatic cockroach (Epilampra sp., Epilampridae). (b) Firefly-mimicking cockroach (Achroblatta luteola, Atticolidae). (c) Firefly model of firefly-mimicking cockroach (Aspisoma sp., Lampyridae). (d) Myrmecophilous cockroach (Myrmecoblatta sp., Atticolidae). (e) Leaf cockroach (Pseudomops sp., Blatellidae).

ing effective, however, during the daytime when the insects are at rest and visible to predators. The lycid mimic Paratropes may be responsible for pollination of plants in the canopy of Central American rain forests (Perry 1978).

The fat body of cockroaches is packed with intracellular bacteria (bacteroids) that contribute to the synthesis of amino acids used in metabolism. The alimentary canal of some wood-feeding types also contain symbiotic protozoa, which, like those of certain termites, assist in the digestion of cellulose (Roth and Willis 1960).

Ecological niches occupied by tropical American cockroaches are extremely varied. Many of these insects are associated casually with vegetation, usually seen sitting on the upper surfaces of leaves (Plectoptera), or are disposed to feed on the fruit, leaves, bark, roots, and other parts of living plants of particular species; others consume the wood of rotting logs. Pseudo-mops (fig. 5.8e) are common, small, brightly colored forms (head orange and wings and pronotum shining dark purple, the latter margined with yellow) that perch on the leaves of low plants in forests and clearings, hopping from place to place in the daytime. Blaberus depends on the excrement or dead bodies of other creatures and lives in animal burrows, hollow trees, or caves. A number of species live symbioti-cally with ants (Bolivar 1905), such as the minute Attiphila, found in the fungus gar dens of leaf cutter ants (Atta), and Myrmecoblatta (fig. 5.8d), a genus associated with carpenter ants (Deyrup and Fisk 1984). Cockroaches have been found in all climes, from hot deserts and cold moun-taintops to warm, humid lowland rain forests. Everywhere they are important reducers of leaf litter and wood. In the inundation forests of Amazonia, Epilampra feeds on dead leaves and insect carcasses. In any one area, as much as 5.6 percent of the yearly leaf fall and other organic detritus may be turned over by members of this genus (Irmler and Furch 1979). There is some tendency for adult cockroaches in lowland forests to disperse their activity over a long time, thereby possibly reducing interspecific competition in nonseasonal locations; their occurrence does not follow this pattern where well-defined wet and dry seasons are present (Wolda and Fisk 1981).

A number of cockroaches are capable of sound production. They accomplish this by rubbing the abdomen against the wings (Blaberus), by stridulation of roughened areas on the thorax (Panchlora), or by other devices (Roth and Hartman 1967).

Of the 3,500 known species in the world, probably over 30 percent are found in Latin America (Princis 1962-1971). No general guide to their classification is available, although there are some good local treatments with broad applicability (Fisk and Wolda 1979, Bruijning 1959).

References

Bolivar, I. 1905. Les blattes myrmecophiles. Schweizerischen Entomol. Ges. Mitt. 11: 134-141.

Bruijning, C. F. A. 1959. The Blattidae of Surinam. Stud. Fauna Suriname Guianas 2(4): 1-103.

Cornwell, P. B. 1968. The cockroach. Vol. 1. Hutchinson, London.

Crowell, H. H. 1946. Notes on an amphibious cockroach from the Republic of Panama. Entomol. News 57: 171-172.

Deyrup, M., and F. Fisk. 1984. A myrmeco-philous cockroach new to the United States (Blattaria: Polyphagidae). Entomol. News 95: 183-185.

Fisk, F. W., and H. Wolda. 1979. Keys to the cockroaches of central Panama. Stud. Neo-trop. Fauna Environ. 14: 177-201.

Gazivoda, P., and D. Fish. 1985. Scanning electron microscope demonstration of bacteria on tarsi of Blatella germanica. New York Entomol. Soc. J. 93: 1064-1067.

Guthrie, D. M., and A. R. Tindall. 1968. The biology of the cockroach. Arnold, London.

Irmler, U., and K. Furch. 1979. Production, energy, and nutrient turnover of the cockroach Epilampra irmleri Roch e Silva and Aguilar in a Central-Amazonia inundation forest. Amazoniana 6: 497-520.

Perry, D. R. 1978. Paratropes bilunata (Orthop-tera; Blattidae): An outcrossing pollinator in a Neotropical wet forest canopy. Entomol. Soc. Wash. Proc. 80: 656-657.

Princis, K. 1962-1971. Blatariae. In M. Beier, ed., Orthopterorum Catalogus. Junk, The Hague. Pts. 3, 4, 6, 7, 8, 11, 13, 14.

Rocha e Silva Albuquerque, I., and S. M. Rodrigues Lopes. 1976. Blattaria de bro-melia (Dictyoptera). Rev. Brasil. Biol. 36: 873-901.

Roth, L. M., and D. W. Alsop. 1978. Toxins of Blattaria. In S. Bettini, ed., Arthropod venoms. Springer, Berlin. Pp. 465-487.

Roth, L. M., and H. B. Hartman. 1967. Sound production and its evolutionary significance in the Blattaria. Entomol. Soc. Amer. Ann. 60: 740-752.

Roth, L. M., and E. R. Willis. 1957. The medical and veterinary importance of cockroaches. Smithsonian Misc. Coll. 134(10): 1-147.

Roth, L. M., and E. R. Willis. 1960. The biotic associations of cockroaches. Smithsonian Misc. Coll. 141: 1-470.

Schal, C., and W. J. Bell. 1986. Vertical community structure and resource utilization in Neotropical forest cockroaches. Ecol Entomol. 11: 411-423. Wolda, H., and F. W. Fisk. 1981. Seasonality of tropical insects. II. Blattaria in Panama, f Anim. Ecol. 50: 827-838.

Domestic Cockroaches

Less than thirty-five species of cockroaches live in intimate closeness with humans. They frequent homes, restaurants, hotels, and all our dwellings, where they scavenge food leavings and whatever edible organic matter they can find (Cornwell 1968), All are Old World in origin, probably carried to Latin America in the last four centuries aboard ships. Some less adaptable species have spotty distributions, reflecting to some degree their points of arrival, while others have spread virtually everywhere.

Probably the most widespread and frequently seen is the American cockroach, or cucarachón (Periplaneta americana; fig. 5.9a), which infests warm dwellings throughout the world (Bell and Adiyodi 1981). It prefers a heated, moist environment and is common outdoors in tropical portions of America as well as indoors. It is often found in sewers. A medium-sized cockroach (BWL 28-44 mm), its body is shining reddish-brown, with a paler yellow area around the edge of the head shield. The fully developed wings extend well beyond the abdomen in the male but only just overlap the abdomen in the female. Females produce up to ninety free oothe-cae with about twelve eggs each.

A related and similarly ubiquitous species is the Australian cockroach (Periplaneta australasiae; fig. 5.9b), which is a general pest in cooler areas wherever moist artificial environments prevail. About the same size (BWL 30-35 mm) and facies as P. americana, it differs primarily in having well-defined, bright yellow "shoulders" (elongate marks at the outer bases of the fore wings). Its biology is also similar to that of the American cockroach, but it seems not to be a denizen of sewers. The

Figure 5.9 COCKROACHES, (a) American cockroach (Periplaneta americana, Blattidae). (b) Australian cockroach (Periplaneta australasiae, Blattidae). (c) Brown-banded cockroach (Supella longi-palpa, Blatellidae). (d) Harlequin cockroach (Neostylopyga rhombifolia, Blattidae). (e) Madeira cockroach (Leucophaea maderae, Oxyhaloidae). (f) Surinam cockroach (Pycnoscelus surinamensis, Pycnoscelididae).

Figure 5.9 COCKROACHES, (a) American cockroach (Periplaneta americana, Blattidae). (b) Australian cockroach (Periplaneta australasiae, Blattidae). (c) Brown-banded cockroach (Supella longi-palpa, Blatellidae). (d) Harlequin cockroach (Neostylopyga rhombifolia, Blattidae). (e) Madeira cockroach (Leucophaea maderae, Oxyhaloidae). (f) Surinam cockroach (Pycnoscelus surinamensis, Pycnoscelididae).

original home of both of these Periplaneta species was probably tropical Africa.

The brown-banded cockroach (Supella longipalpa, sometimes called S. supellectil-ium; fig- 5.9c) is small (BWL 10-14 mm), with complete wings in the male and shortened wings in the female. It is buff in general color but with two suffuse, transverse black or brown bands. It is highly domiciliary, taking up residence in furniture and forming colonies in drawers, behind pictures on the wall, on bookshelves, and in like places. Here the adults and nymphs hide by day, emerging at night to feed on any available fodder, including glue, sizing on books, wallpaper, food scraps, and even plain paper.

The harlequin cockroach (Neostylopyga rhombifolia; fig. 5.9d) is medium-sized (BL 20-25 mm) and completely without wings in both sexes, although the fore wings are represented by small stubs below the outer corners of the head shield. It has a striking color pattern of deep yellow marbling on a shining, brownish-black background. Its biology is largely unstudied, although it is common both indoors and out.

The Madeira cockroach (Leucophaea maderae; fig. 5.9e), known as barata cascuda in Brazil, has become widely established around the Carribean, where it often is a serious pest in homes and warehouses, and in many parts of South and Central America. In tropical environments, it lives out doors and is common in sugarcane and banana plantations. It is a fairly large cockroach (BWL 4—5 cm), with ample wings in both sexes. It is pale brown to tawny olive in general color, the fore wings marked with a dark spatter pattern over most of their surface; the basal and anterior marginal areas are contrastingly plain, except for a dark linear arc running obliquely across the wing base. Adults are slow moving but capable of defending themselves well with an offensive odor. They also stridulate. Females bear twenty-five to thirty live young at a time.

Although first found in South America, the Surinam cockroach (Pycnoscelus surinamensis; fig. 5.9f), known as barata de pau podre in Brazil, is most likely of Oriental origin. Because it is parthenogenetic, even un-mated females can start thriving populations wherever they happen to be carried, and the species has become established widely in Latin America. Away from civilization, it occurs under stones and loose litter and can burrow superficially into the soil. It is medium-sized (BWL 18-24 mm), shining brown, with dark shoulder streaks and a contrasting black head shield. Wings are complete in both sexes. It often has a pale band along the anterior margin of the head shield, the posterior margin of which is strongly sinuate.

Another domiciliary cockroach from Africa is the lobster cockroach (also called the

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