56 [March, 



summers, and bids well to be more so in tbe present season. The 

 rapidity at wbicb introduced insects increase and disperse in New 

 Zealand is unprecedented. Like Eristalis tenax and M. vomitoria, 

 Gastrophilus nasalis, Linn., is another case in point. Four years ago 

 this month it first attacked some draught horses at work at Chertsey, 

 twelve miles from Ashburton. Since then it has spread with alarming 

 rapidity from Auckland to the Bluff, and has caused serious loss and 

 trouble among horses. Excepting the three forms of Bomli, now 

 naturalized in New Zealand, all other insects are accidental in- 

 troductions. I do not here include BapJiidia, introduced by Mr. 

 Koebele two years ago, as nothing is known, at present, respecting its 

 success or failure, in establishing itself. It is remarkable that M. 

 vomitoria has only been observed in New Zealand within the last few 

 years. Since the direct mail service began between England and New 

 Zealand, the facilities for transmission of the species have been more 

 favourable than previously. In this connection it would be of interest 

 to know if M. vomitoria has been observed at the several ports of call 

 on the steamer's line of route, viz. : Teneriffe, Cape Town, and Hobart. 

 Its recent occurrence and rapid inerease in New Zealand seems to me 

 to favour the probability of its introduction since the advent of the 

 direct steamers arriving fortnightly from England. 



In nearly every instance both the noxious and beneficial species 

 now naturalized in New Zealand have been introduced unobserved. 

 When once established, many species have increased at a marvellous 

 ratio, and with disastrous results. Mr. Maskell's paper on " Migrations 

 and New localities of some Coccids (Ent. Mo. Mag., xxviii, p. 69) is full 

 confirmation, and is applicable to many species belonging to other 

 groups. 



In a valuable paper by Baron Osten Sacken on " Facts concerning 

 the importation or non-importation of Diptera into distant countries " 

 (Trans. Ent. Soc. Lend., 1884, pp. 489 — 496), the distinguished 

 Dipterologist discussed the question of the transportation of Diptera. 

 In harmony with his remarks I may safely say that the trans-oceanic 

 migration of nearly all the exotic Diptera now flourishing in New 

 Zealand has been accomplished artificially, and especially so by fast 

 steamers during recent years. The genial climate of the islands, with 

 long summers and mild winters, is extremely favourable to the habits 

 and development of Diptera from colder climes. It is possible that 

 fresh immigrants of previously introduced species may continue to 

 arrive, especially if the fast steamers leave England or the ports of 

 call during the summer months. I imagine that M. vomitoria may 



