Geographical Distribution of Insects. 107 



out his knowledge, to great distances ; as has been the case, 

 for example, with the common hive-bee, which he has intro- 

 duced into the new continent, and the Blatta Americana 

 which he has conveyed to Europe, where it is now completely 

 acclimatised.* With regard to stations, he modifies them by 

 changing the vegetation, the temperature, and other physical 

 conditions. Of this we are comparatively insensible in coun- 

 tries like those of Eiu-ope, which have been cultivated from 

 time immemorial, but it is striking in those which are covered 

 Avith primitive forests. M. Lacordaire has observed, as a com- 

 mon occurrence both in Brazil and Cayenne, that wherever 

 the natural wood was cut down for the purpose of forming a 

 plantation, along vnth the new plants new insects appeared 

 which were but very rarely seen in the smTounding forests. 

 Thence in these countries, the researches of the entomologist 

 instead of being retarded by the burnmg of the forests, are 

 rendered more fruitful. If these clearings, however, are 

 made on a very large scale, the contrary sometimes takes 

 place. M. A. de Saint-Hilaire has noticed that insects have 

 disappeared almost entkely from the plateaus of the province 

 of Minas and Brazil, since they were deprived of wood, and 

 overrun by a graminivorous parasite, the Capiagordiira, which 

 chokes all the other plants. 



Influence of Locomotion. — It is evident that the influence of 

 this cause will be the more powerful in proportion as the spe- 



* M. Lacordaire mentions tlie following as a curious instance of the man- 

 ner in which insects are sometimes transported to great distances from 

 their native haunts. In 1825, when on his way from Buenos Ayres to 

 France, he found, when under the line, a living example of monochamiis siitor, 

 an insect of the north of Europe, and an inhabitant of Britain, clinging to 

 the shrouds of the vessel. Shortly after, the sailors brought him several 

 others which they had found in other places. The carpenter having occa- 

 sion to cut a plank of fir, several monochami issued from their holes, to the 

 amount of about a dozen. The insects had thus travelled from Norway 

 to France, then from France to Buenos Ayres, where some of them must 

 have been disclosed, but it is doubtful whether they could have been ac- 

 climatised there, as there are no pines. Many examples might be men- 

 tioned similar to this : monochamus dentator, a North American species, has 

 been taken at Havre ; cordyloccra nitidipeiuii, a native, of Senegal, near Paris ; 

 a, pyropkorus (one of the luminous elateridse) in the same city ; and to men- 

 tion no others, the huge bird-spider (mygalc aticularia) at Rouen. 



