Common Name: German cockroach
Scientific Name:Blattella germanica (Linnaeus)
Description: The adult German cockroach is about 5/8 inch long, overall light brown in color and wings which cover the abdomen. The thoracic shield just behind the head (pronotum) is marked with two prominent black stripes. Immature stages (nymphs) are smaller, wingless and have a pale stripe (on at least the second and third thoracic segments in first stage nymphs) running lengthwise down the middle of the darker brown body.
The field cockroach, Blattella vaga Hebard, is similar to the German cockroach in appearance, but it occurs primarily outdoors where it feeds on decaying plant materials. Compared to the German cockroach, it is more active during daylight hours and will be found around lights. They also are known to fly when disturbed. The brownbanded cockroach, Supella longipalpa (Fabricius) is about the same size as the German cockroach, but appear ” banded” because the wings are marked with a pale brown band at the base and another about a third of the distance from the base.
Life Cycle: Simple metamorphosis. Mated females produce an egg capsule that is attached to the end of the abdomen for up to a month before being dropped a day or so before eggs hatch. Each 5/16 inch long, brown egg capsule contains 30 to 40 eggs which hatch in 2 to 4 days after being deposited. Nymphs hatching from eggs are less than 1/8 inch long and wingless. They develop through 6 to 7 stages (instars) over 74 to 85 days (varying with temperature) before becoming adults. There may be four generations per year.
Habitat, Food Source(s), Damage: This is mainly an indoor species although they will also migrate outdoors from structure to structure. Occasionally, new infestations begin by bringing in cartons and other materials from infested structures that harbor the roaches or their eggs. Kitchens, bathrooms and other locations that provide food, moisture, warmth and shelter are preferred habitats. German cockroaches are mainly active at night, when they search for food and water. During the day, they remain concealed in cracks and crevices unless they are over-crowded, with all developmental stages occurring together. They also can occur in attics, wall voids, crawl spaces, foundation cracks, garbage areas and around the landscape. May spread food contaminants. Some people have allergic reactions to cockroaches or cockroach residues (e.g., feces, body extracts).
Pest Status: One of the most common household cockroach pests in the state; presence in homes is a nuisance and they may spread food contaminants. Some people have allergic reactions to cockroaches or cockroach residues (e.g., feces, body extracts).
Common name: American cockroach
Scientific name: Periplaneta americana Linnaeus
Description: This is one of the largest common cockroaches in Texas, reaching 1-1/2 to 2 inches. They are reddish-brown in color. The shield portion behind the head (prothorax) has a margin of light brown or yellow.
Another similarly-sized, black-brown, common indoor species is the oriental cockroach, Blatta orientalis Linnaeus, but it differs because the wings on adults are rudimentary on the female and only cover 75% of the abdomen of the male. Other cockroach species come in a variety of sizes and shapes. Most are dark brown with or without color patterns on the body. Occasionally, a whitish cockroach is observed incorrectly thought to be an “albino” form. These are, in fact, roaches that have just molted and have not yet had time to darken their “new” exoskeleton.
There is, however, a pale green cockroach species, the Cuban cockroach, Panchlora nivea (Linnaeus) (Blattodea:Blaberidae), that is occasionally encountered in the Houston area. Other common outdoor species include wood roaches, Parcoblatta spp. (Blatellidae) and the pale-bordered field cockroach, Pseudomops septentrionalis Hebard (Blattaria: Blattellidae).
Life Cycle: Simple metamorphosis (egg, nymph, adult). Female cockroaches glue or drop 1/4 inch long bean-like egg capsules (oothecae) containing about 15 eggs on or around infested areas. Nymphs hatch from the egg case that resemble small grayish-brown adult cockroaches without fully developed wings. Nymphs molt 10 to 13 times in over a year (470 to 600 days, depending on temperature) before becoming adults.
Habitat, Food Source(s), Damage: This is generally an outdoor species, living in wood piles, decaying trees, palm trees and in sewer systems. Cockroaches have flattened bodies that allow them to enter homes through cracks around loose-fitting doors and windows, and where electric lines or pipes pass through walls. They are mainly active at night and hide in cracks and crevices during the day, preferring dark moist sites in attics and basements. Cockroaches eat almost anything including meats and grease, starchy foods, sweets, baked goods, leather, wallpaper paste, book bindings and sizing. Adults are capable of gliding flights.
Pest Status: Although not shown to be direct carriers of disease, they can contaminate food and kitchen utensils with excrement and salivary secretions and leave an unpleasant odor.