CHAPTER III.

THE NATURAL HISTORY OF THE COCKROACH.

_SPECIAL REFERENCES._

HUMMEL. Essais Entomologiques, No. 1 (1821).

CORNELIUS. Beiträge zur nähern Kenntniss von Periplaneta orientalis (1853.)

GIRARD. La domestication des Blattes. Bull. Soc. d’Acclimatisation, 3^e Sér., Tom. IV., p. 296 (1877).

_Range._

The common Cockroach is native to tropical Asia,[14] and long ago made its way by the old trade-routes to the Mediterranean countries. At the end of the sixteenth century it appears to have got access to England and Holland, and has gradually spread thence to every part of the world.

[14] Linnæus was certainly mistaken in his remark (Syst. Nat., 12th ed.) that this species is native to America, and introduced to the East--“Habitat in America: hospitatur in Oriente.” He adds, “Hodie in Russiæ adjacentibus regionibus frequens; incepit nuperis temporibus Holmiæ, 1739, uti dudum in Finlandia.”

Perhaps the first mention of this insect in zoological literature occurs in Moufet’s Insectorum Theatrum (1634), where he speaks of the Blattæ as occurring in wine cellars, flour mills, &c., in England. It is hard to determine in all cases of what insects he is speaking, since one of his rude woodcuts of a “Blatta” is plainly _Blaps mortisaga_; another is, however, recognisable as the female of _P. orientalis_; a third, more doubtfully, as the male of the same species. He tells how Sir Francis Drake took the ship “Philip,”[15] laden with spices, and found a great multitude of winged Blattæ on board, “which were a little larger, softer, and darker than ours.” Perhaps these belonged to the American species, but the description is obscure. Swammerdam also was acquainted with our Cockroach as an inhabitant of Holland early in the seventeenth century. He speaks of it as “insectum illud Indicum, sub nomine Kakkerlak satis notum,” and very properly distinguishes from it “the species of Scarabæus” (_Blaps_), which Moufet had taken for a Blatta.[16]

[15] This must have been the “San Felipe,” a Spanish East Indiaman, taken in 1587. See Motley, United Netherlands, Vol. II., p. 283.

[16] Biblia Naturæ, Vol. I., p. 216.

The American Cockroach is native to tropical America, but has now become widely spread by commerce. An Australian species also (_P. australasiæ_) has begun to extend its native limits, having been observed in Sweden,[17] Belgium, Madeira, the East and West Indies,[18] Florida,[19] &c. In Florida it is said to be the torment of housekeepers.

[17] De Borck. Skandinaviens rätvingade Insekters Nat. Hist., I., i., 35.

[18] Brunner. N. Syst. d. Blattaires, p. 234.

[19] Scudder. Proc. Boston Soc. N.H., Vol. XIX., p. 94.

To the genus _Blatta_ belong a number of small European species, which mostly lurk in woods and thickets. Some of these are found in the south of England. _B. lapponica_ is one of the commonest and most widely distributed. It is smaller than the common Cockroach, and both sexes have long wings and wing-cases. The males are black and the females yellow. It is found on the mountains of Norway and Switzerland as high as shrubs extend, and when sheltered by human dwellings, can endure the extreme cold of the most northern parts of Europe. This is the insect of which Linnæus tells, that in company with _Silpha lapponica_ it has been known to devour in one day the whole stock of dried but unsalted fish of a Lapland village. _B. germanica_ also has the wings and wing-cases well developed in both sexes. Two longitudinal stripes on the pronotum, or first dorsal plate of the thorax, are the readiest mark of this species, which is smaller and lighter in colour than the common Cockroach. It is plentiful in most German towns, and has been introduced from Germany into many other countries;[20] but it appears to be native, not to Germany alone, but to Asia and all parts of central and southern Europe. Where and how it first became domesticated we do not know.

[20] For example, the Russians often call it _Proussaki_, the Prussian Cockroach, and believe that their troops brought it home with them after the Seven Years’ War. The native Russian name is _Tarakan_. In Finland and Sweden the same species is called _Torraka_, which appears to be a corruption of the Russian word, and confirms the account of Linnæus quoted above.

_B. germanica_ is found in the United States from the Atlantic to the Pacific. It is generally known as the Croton Bug, because in New York it is often met with about the water pipes, which are supplied from the Croton River (Dr. Scudder).

The other species of Cockroaches which have been met with in Europe are _Panchlora maderæ_, said by Stephens to be occasionally seen in London, and _Blabera gigantea_ the Drummer of the West Indies, which has often been found alive in ships in the London Docks.

_Blatta germanica_, _Periplaneta orientalis_, and _P. americana_, are so similar in habits and mode of life as to be interchangeable, and each is known to maintain itself in particular houses or towns within the territory of another species, though usually without spreading.

_Orientalis_ is, for example, the common Cockroach of England, but _germanica_ frequently gets a settlement and remains long in the same quarters. H. C. R., in Science-Gossip for 1868, p. 15, speaks of it as swarming in an hotel near Covent Garden, where it can be traced back as far as 1857. In Leeds, one baker’s shop is infested by this species; it is believed to have been brought by soldiers to the barracks, after the Crimean war, and to have been carried to the baker’s in bread-baskets. We have met with no instance in which it has continued to gain ground at the expense of _orientalis_. _Americana_ also seems well established in particular houses or districts in England. H. C. R. (loc. cit.) mentions warehouses near the Thames, Red Lion and Bloomsbury Squares, and the Zoological Gardens, Regent’s Park. It frequents one single warehouse in Bradford, and is similarly local in other towns with foreign trade.

Many cases are recorded in which _germanica_ has been replaced by _orientalis_, as in parts of Russia and Western Germany, but detailed and authenticated accounts are still desired. On the whole _orientalis_ seems to be dominant over both _germanica_ and _americana_.

The slow spread of the Cockroaches in Europe is noteworthy, not as exceptional among invading species, but as one more illustration of the length of time requisite for changes of the equilibrium of nature. It took two centuries from the first introduction of _orientalis_ into England for it to spread far from London. Gilbert White, writing, as it would appear, at some date before 1790, speaks of the appearance of “an unusual insect,” which proved to be the Cockroach, at Selborne, and says: “How long they have abounded in England I cannot say; but have never observed them in my house till lately.”[21] It is probable that many English villages are still clear of the pest. The House Cricket, which the Cockroaches seem destined to supplant, still dwells in our houses, often side by side with its rival, sharing the same warm crannies, and the same food. The other imported species, though there is reason to suppose that they cannot permanently withstand _orientalis_, are by no means beaten out of the field; they retreat slowly where they retreat at all, and display inferiority chiefly in this, that in countries where both are found, they do not spread, while their competitor does. It may yet require some centuries to settle the petty wars of the Cockroaches.

[21] Bell’s Edition, Vol. I., p. 454.

It is also worth notice that in this, as in most other cases, the causes of such dominance over the rest as one species enjoys are very hard to discover. We cannot explain what peculiarities enable Cockroaches to invade ground thoroughly occupied by the House Cricket, an insect of quite similar mode of life: and it is equally hard to account for the superiority of _orientalis_ over the other species. It is neither the largest nor the smallest; it is not perceptibly more prolific, or more voracious, or fonder of warmth, or swifter than its rivals, nor is it easy to see how the one conspicuous structural difference--viz., the rudimentary state of the wings of the female, can greatly favour _orientalis_. Some slight advantage seems to lie in characteristics too subtle for our detection or comprehension.

_Food and Habits._

As to the food of Cockroaches, we can hardly except any animal or vegetable substance from the long list of their depredations. Bark, leaves, the pith of living cycads, paper, woollen clothes, sugar, cheese, bread, blacking, oil, lemons, ink, flesh, fish, leather, the dead bodies of other Cockroaches, their own cast skins and empty egg-capsules, all are greedily consumed. Cucumber, too, they will eat, though it disagrees with them horribly.

In the matter of temperature they are less easy to please. They are extremely fond of warmth, lurking in nooks near the oven, and abounding in bakehouses, distilleries, and all kinds of factories which provide a steady heat together with a supply of something eatable. Cold is the only check, and an unwarmed room during an English winter is more than they can endure. They are strictly nocturnal, and shun the light, although when long unmolested they become bolder. The flattened body enables the Cockroach to creep into very narrow crevices, and during cold weather it takes refuge beneath the flags of a kitchen floor, or in other very confined spaces.

The Cockroach belongs to a miscellaneous group of animals, which may be described as in various degrees parasitic upon men. These are all in a vague sense domestic species, but have not, like the ox, sheep, goat, or pig, been forcibly reduced to servitude; they have rather attached themselves to man in various degrees of intimacy. The dog has slowly won his place as our companion; the cat is tolerated and even caressed, but her attachment is to the dwelling and not to us; the jackal and rat are scavengers and thieves; the weasel, jackdaw, and magpie are wild species which show a slight preference for the neighbourhood of man. All of these, except the cat, which holds a very peculiar place, possess in a considerable degree qualities which bring success in the great competitive examination. They are not eminently specialised, their diet is mixed, their range as natural species is wide. Apart from man, they would have become numerous and strong, but those qualities which fit them so well to shift for themselves, have had full play in the dwellings of a wealthy and careless host. Of these domestic parasites at least two are insects, the House-fly and the Cockroach; and the Cockroach in particular is eminent in its peculiar sphere of activity. The successful competition of Cockroaches with other insects under natural conditions is sufficiently proved by the fact that about nine hundred species have already been described,[22] while their rapid multiplication and almost worldwide dissemination in the dwellings of man is an equally striking proof of their versatility and readiness to adapt themselves to artificial circumstances. In numerical frequency they probably exceed all domestic animals of larger size, while in geographical range the five species, _lapponica_, _germanica_, _orientalis_, _americana_, and _australasiæ_, are together comparable to the dog or pig, which have been multiplied and transported by man for his own purposes, and which cover the habitable globe.

[22] British Museum Catalogue of Blattariæ (1868) and Supplement (1869). It is probable that the number is over-estimated in this catalogue, the same species being occasionally renamed.

_The Cockroach a persistent type._

The Cockroach is historically one of the most ancient, and structurally one of the most primitive, of our surviving insects. Its immense antiquity is shown by the fact that so many Cockroaches have been found in the Coal Measures, where about eighty species have been met with. The absence of well-defined stages of growth, such as the soft-bodied larva or inactive pupa, the little specialised wings and jaws, the simple structure of the thorax, the jointed appendages carried on the end of the abdomen, and the unconcentrated nervous system, are marks of the most primitive insect-types. The order Orthoptera is undeniably the least specialised among winged insects at least, and within this order none are more simple in structure, or reach farther back in the geological record than the Cockroaches. The wingless Thysanura are even more generalised, but their geological history is illegible.[23]

[23] Brongniart has just described a Carboniferous Insect which he considers a Thysanuran (_Dasyleptus Lucasi_), though it has but one anal appendage. See C. R. Soc. Ent., France, 1885.

_Life-History._

The eggs of the Cockroach are laid sixteen together in a large horny capsule. This capsule is oval, with roundish ends, and has a longitudinal serrated ridge, which is uppermost while in position within the body of the female. The capsule is formed by the secretion of a “colleterial” gland, poured out upon the inner surface of a chamber (vulva) into which the oviducts lead. The secretion is at first fluid and white, but hardens and turns brown on exposure to the air. In this way a sort of mould of the vulva is formed, which is hollow, and opens forwards towards the outlet of the common oviduct. Eggs are now passed one by one into the capsule; and as it becomes full, its length is gradually increased by fresh additions, while the first-formed portion begins to protrude from the body of the female. When sixteen eggs have descended, the capsule is closed in front, and after an interval of seven or eight days, is dropped in a warm and sheltered crevice. In _Periplaneta orientalis_ it measures about ·45 in. by ·25 in. (fig. 5). The ova develop within the capsule, and when ready to escape are of elongate-oval shape, resembling mummies in their wrappings. Eight embryos in one row face eight others on the opposite side, being alternated for close packing. Their ventral surfaces, which are afterwards turned towards the ground, are opposed, and their rounded dorsal surfaces are turned towards the wall of capsule; their heads are all directed towards the serrated edge. The ripe embryos are said by Westwood to discharge a fluid (saliva?) which softens the cement along the dorsal edge, and enables them to escape from their prison. In _Blatta germanica_ the female is believed to help in the process of extrication.[24] The larvæ are at first white, with black eyes, but soon darken. They run about with great activity, feeding upon any starchy food which they can find.

[24] Hummel, loc. cit.

The larvæ of the Cockroach hardly differ outwardly from the adult, except in the absence of wings. The tenth tergum is notched in both sexes, as in the adult female. The sub-anal styles of the male are developed in the larva.

Cornelius, in his Beiträge zur nähern Kenntniss von Periplaneta orientalis (1853), gives the following account of the moults of the Cockroach. The first change of skin occurs immediately after escape from the egg-capsule, the second four weeks later, the third at the end of the first year, and each succeeding moult after a year’s interval. At the sixth moult the insect becomes a pupa,[25] and at the seventh (being now four years old) it assumes the form of the perfect Insect. The changes of skin are annual, and like fertilisation and oviposition, take place in the summer months only. He tells us further that the ova require about a year for their development. These statements are partly based upon observation of captive Cockroaches, and are the only ones accessible; but they require confirmation by independent observers, especially as they altogether differ from Hummel’s account of the life-history of _Blatta germanica_, and are at variance with the popular belief that new generations of the Cockroach are produced with great rapidity.

[25] The use of the term _pupa_ to denote the last stage before the complete assumption of wings in the Cockroach, is liable to mislead. There is no resting-stage at all; wings are developed gradually, and are nearly as conspicuous in the last larval state as in the so-called pupa. There seems no reason for speaking of pupæ in this case.

It is preferable to designate as “nymphs” young and active Insects, immature sexually, but with mouth-parts like those of the adult. See Lubbock, Linn. Trans., 1863, and Eaton, Linn. Trans., 1883.

The antennæ of the male nymph resemble those of the adult female. Wings and wing-covers appear first in the later larval stages, but are then rudimentary, and constitute a mere prolongation of the margins of the thoracic rings. Cornelius says that the round white spot internal to the antenna first appears plainly in the pupa, but we have readily found it in a very young larva. The Insect is active in all its stages, and is therefore, with other Orthoptera, described as undergoing “incomplete metamorphosis.” After each moult it is for a few hours nearly pure white. Of the duration of life in this species we have no certain information, and there is great difficulty in procuring any.

_Sexual Differences._

Male Cockroaches are readily distinguished from the females by the well-developed wings and wing-covers. They are also slighter and weaker than the females; their terga and sterna are not so much thickened; their alimentary canal is more slender, and they feed less greedily (the crop of the male is usually only half-full of food). They stand higher on their legs than the females, whose abdomen trails on the ground. The external anatomical differences of the sexes may be tabulated thus:--

_Female._ | _Male._ | Antenna shorter than the body, | Antenna rather longer than the third joint longer than | the body, the third joint the second. | about as long as the second. | Wings and wing-covers rudimentary. | Wings and wing-covers well | developed. | Mesosternum divided. | Mesosternum entire. | Abdomen broader. | Abdomen narrower. | Terga 8 and 9 not externally | Terga 8 and 9 externally visible. | visible. | The 10th tergum notched. | The 10th tergum hardly | notched. | The 7th sternum divided behind. | The 7th sternum undivided. | The external outlet of the | The outlet between the 10th rectum and vulva between | tergum and the 9th sternum. the 10th tergum and the | 7th sternum. | | No sub-anal styles. | Sub-anal styles.

_Parasites._

We have before us a long list of parasites[26] which infest the Cockroach. There is a conferva, an amœba, several infusoria, nematoid worms (one of which migrates to and fro between the rat and the Cockroach), a mite, as well as hymenopterous and coleopterous Insects. The Cockroach has a still longer array of foes, which includes monkeys, hedgehogs, pole-cats, cats, rats, birds, chamæleons, frogs, and wasps, but no single friend, unless those are reckoned as friends which are the foes of its foes.

[26] See Appendix.

_Names in common use._

A few lines must be added upon the popular and scientific names of this insect. Etymologists have found it hard to explain the common English name, which seems to be related to _cock_ and _roach_, but has really nothing to do with either. The lexicographers usually hold their peace about it, or give derivations which are absurd. Mr. James M. Miall informs us that “_Cockroach_ can be traced to the Spanish _cucarácha_, a diminutive form of _cuco_ or _coco_ (Lat. _coccum_, a berry). _Cucarácha_ is used also of the woodlouse, which, when rolled up, resembles a berry. The termination _-ácha_ (Ital. _-accio_, _-accia_) signifies _mean_ or _contemptible_. The Spanish word has also taken a French form; at least _coqueraches_ has some currency (see, for example, Tylor’s Anahuac, p. 325).” In provincial English _Black Clock_ is a common name. The German word _Schabe_, often turned into _Schwabe_, means perhaps _Suabian_, as Moufet, quoting Cordus, seems to explain.[27] _Franzose_ and _Däne_ are other German words for the insect, applied specially to _Blatta germanica_; and all seem to imply some popular theory as to the native country of the Cockroach.[28] This etymology of _Schabe_ is not free from suspicion, particularly as the same term is commonly applied to the clothes-moth. _Kakerlac_, much used in France and French-speaking colonies, is a Dutch word of unknown signification. _P. Americana_ is usually named _Kakerlac_ or _Cancrelat_ by the French; while _orientalis_ has many names, such as _Cafard_, _Ravet_, and _Bête noire_.[29] The name _Blatta_ was applied by the ancients to quite different insects, of which Virgil and Pliny make mention; _Periplaneta_ is a modern generic term, coined by Burmeister.

[27] Insectorum Theatrum, p. 138. The name _Schwabe_ is frequent in Franconia, where it is believed to have taken origin. Suabia adjoins Franconia, to the south.

[28] Compare the Swedish name (_supra_, p. 18).

[29] A fuller list of vernacular names is given by Rolland, Faune Populaire de la France, Vol. III., p. 285. See also Nennich, Polyglotten Lexicon, Vol. I., p. 620.

_Uses._

Of the uses to which Cockroaches have been put we have little to say. They constitute a popular remedy for dropsy in Russia, and both cockroach-tea and cockroach-pills are known in the medical practice of Philadelphia. Salted Cockroaches are said to have an agreeable flavour which is apparent in certain popular sauces.