Insect guide > Cockroaches

Cockroaches


Cockroaches(Family Blattidae.)
The insects of this family, known commonly as form the old group Cursoria, or runners. The body as a rule is oval and flat, all the legs being similar in form. The head is deflexed or bent under and generally concealed by the prothorax.

The hind wings are slightly folded. The insects of this group are very abundant in the tropics but several species have become spec domesticated and are very abundant in the colder parts of the world. The cockroach type is a very persistent one, and insects of this family cockroaches, existed in great numbers in geologic periods prior to the tertiary. They are found in considerable number in carboniferous rocks and one form has been found in Silurian sandstone.

The eggs are laid in egg cases as with the Mantidae but the subsequent supposed that they grow very slowly. Most of them are nocturnal in their habits. They feed on a great variety of substances, especially those forms which inhabit houses, but it is supposed that their natural food is dead animal matter. Dr. Sharp estimates that there are five thousand species in existence.

The species found in American houses are the American cockroach (Periplaneta americana), the German cockroach or croton bug (Ectobia germanica), the European cockroach or "black beetle" as it is known in England (Periplaneta orientalis) and the Australian cockroach (Periplantea australasiae).

The female carries the egg case with her until she finds a proper place to leave it or until the eggs are nearly ready to hatch. The young roaches grow slowly and pass through a variable number of molts, sometimes as many as seven. The time required for the development from the egg to the adult may be prolonged by absence of food or low temperature. Four or five years have been said to have been occupied in this growth.

The German cockroach has been shown to reach full-growth in from four and one-half to six months and the American cockroach has been raised from the egg to the adult in about twelve months.

The anatomy of Periplaneta orientates has been carefully studied by Miall and Denny and the American household cockroaches have been treated at some length by Marlatt.

The cockroaches which have just been mentioned are practically domesticated animals in so far as they have accommodated themselves to the environments of civilization. They appear to eat almost everything, whether animal or vegetable in its nature, and they are household pests of the highest rank. They are also all of them cosmopolitan, or practically so, and have been carried in ships to almost all parts of the world.

Our native cockroaches are, most of them, out-door feeders and are exceptionally cleanly insects. In fact, any one of the domestic cockroaches, if watched, will be seen constantly to make efforts to beautify its person, licking its legs and its antennae in much the same manner in which a cat washes its paws. A curious observation which the writer once made indicates that it is possible for cockroaches to acquire the tobacco habit.

Cockroaches are fond of darkness. They roam about houses at night, and new houses become stocked with roaches through migrations at night time from over-supplied adjoining establishments. On a dark day in Washington I once saw a migrating army of cockroaches, incalculable in number, crossing the street from a dirty restaurant toward buildings apposite. The majority of the individuals composing the army were females carrying egg cases, and the observation thus became one of psychological interest since the migratory instinct seemed to have been developed by an appreciation of the fact that while the restaurant might support the mothers there would not be food enough for the coming children.