6o 



HARDWICKE'S SCI ENCE-GOSSIF. 



occasionally seen in London, and Blabera gigantea, 

 the drummer of the West Indies, has often been 

 found alive in ships in the London Docks. 



Blatta Gerrrianica, Pcriplaneta 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 Gcrmanica frequently gets a settle- 

 ment 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 



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 1 790, speaks of the appearance of 

 "an unusual insect,'' which proved to be the cock- 

 roach, at Selborne, and says : " How long they have 

 abounded in England I cannot say ; but have never 

 observed them in my house till lately." ■" It is 

 probable that many English villages are still clear o£ 

 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 im- 

 ported species, though there is reason to suppose that 



Fig. -i^.— Blatta (^Periplaneta) orientalis, male. Twice 

 natural size. 



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 Blooms- 

 bury 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 Gertnanica 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 



Fig-. ?.7— Blatta {Pe- 

 riplaneta) orien- 

 talis, female. Twice 

 natural size. 



Fig. 3S. — Capsule of Cockroach. A, ex- 

 ternal view ; u, opened ; c, end view. 



they cannot permanently withstand 0)-ientalis, 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. 



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 



• Bell's edition, vol. i. p. 454. 



