1066 



CESARE BARONI URBANI 



differentiated a small geographical race each, which are common to ail the islancfr 

 of the archipelago. But the author, after a study of the whole geographical varie 

 tion of thèse species, prefers not to propose new names for them. The resull 

 of the study of the ant population are compared with the populations of the bes 

 known groups from the same area: Plants and Orthopteroidea. For ail thèse thre 

 groups an explanation of the origin of population by means of palaeogeographicri 

 data is almost impossible. On the other hand, a multiple linear régression, base 

 on the hypothesis that islands have been invaded by propagulae in a relativell 

 récent period, has given a good degree of fitness. The results suggest that one o 

 a few islands have been invaded by propagulae from the Italian peninsula an; 

 that thèse islands serve as stepping stones for the définitive population of th 

 whole archipelago. Some additional conclusions on theoretical islands bic 

 geography have been reached. In particular, the author suggests that most of th' 

 propagulae should be aereal, and that they fly passively on a trajectory whic 

 might approximate a parabola. If this is so, small islands will have a nlter-effec! 

 on propagular flow proportional to their altitude, but, after a given threshold, th, 

 greater incidence of propagulae is determined by the area. Thèse hypothesis ar] 

 confirmed by the cases examined and discussed in the text. 



LITERATUR 



— 1969. Carta geologica d'Italia. Foglio 126 (Isola d'Elba). 

 Arrhenius, O. 1921. Species and area. J. Ecol. 9: 95-99. 

 Baccetti, B. 1954. Contributo alla conoscenza delV Ortotterofauna délia Toscana conti 



nentale. Redia 39: 75-155. 



— 1968. Notulae orthopterologicae. XXV. Ortotteroidei délie isole Pianosa a Monte 



cristo. Atti Soc. tosc. Sci. nat. Mem., Ser. B, 75: 79-94. 

 Baroni Urbani, C. 1966. Ulteriori osservazioni ed esperienze sulla monoginia dei Foi 

 micidi : saggio di un'analisi del comportamento in Leptothorax exilis Err 

 Insectes soc. 13: 173-184. 



— 1967. Le disîribuzioni geografiche discontinue dei For micidi mirmecobiotici. Arct 



bot. biogeogr. ital. 43: 355-365. 



— 1968a. Studi sulla mirmecofauna d'Italia. VI. Il popolamento mirmecologico dell 



isole Maltesi. Arch. bot. biogeogr. ital. 44: 224-241. 



— 19686. Studi sulla mirmecofauna d'Italia. VII. U isola di Montecristo. Atti Soc 



tosc. Sci. nat. Mem., Ser. B. 75: 95-107. 



— 1968c. Studi sulla mirmecofauna d'Italia. VIII. V isola di Giannutri ed alcuni scog 



minori delV Arcipelago Toscano. Atti Soc. tosc. Sci. nat. Mem. Ser. 

 75: 325-338, 1 tab. 



— 1970. Catalogo délie specie di Formicidae d'Italia (Studi sulla mirmecofaun 



d'Italia. IX). Mem. Soc. ent. ital. (im Druck). 

 Bernard, F. 1968. Faune de V Europe et du Bassin méditerranéen. 3. Les fourmis (Hyme 

 noptera Formicidae) d'Europe occidentale et septentrionale. Paris, 411 p 



