133 
one place to another in their undeveloped or adolescent stages.* Le 
Baron, in his studies of the Oyster-shell Bark-Louse of the Apple and one 
of its parasites (A phelinus mytilaspidis), transported scale-covered twigs 
during winter from Geneva, IIl., to Galena, I11., with beneficial results. 
The experiment was conducted on a small scale, but the parasites 
issued and became domiciled in their new locality, thus proving the 
practicability of his scheme. In neither my own experiments nor in Le 
Baron’s, however, was sufficiently thorough examination made to prove 
that the parasites did not already exist in the localities in which they 
were colonized. 
Planchon and myself introduced Tyroglyphus phylloxere trom America 
into France in 1873,+ and it became fully established, as subsequent 
correspondence and observation showed. In 1874 efforts were made 
to send over from England to New Zealand certain Aphid parasites to 
check the alarming increase of those plant pests there, and while I have 
no records at hand to show with what success, the later successfulintro- 
duction of bumblebees to the latter country to fertilize the red clover 
is well-known history. In his report upon the parasites of Coccide in 
the Annual Report of the Department of Agriculture for 1880, Mz. 
Howard gave the subject some theoretical attention and elaborated 
upon the ease with which Coccid parasites could be transported from 
one part of the country to another during winter. He suggested the 
experiment of transporting Dilophogaster californica from the Pacific 
coasttocertainof theSoutheastern States, where itmight be expected to 
prey upon certain large species of Lecanium. In 1883, after previous 
futile attempts by myself and Mr. Otto Lugger, and with the assistance 
of G. C. Bignell, esq., of Plymouth, England, the living cocoons of 
Microgaster glomeratus, a common European parasite of Pieris rapa, 
were successfully imported by the Department and the colonization of 
the species was established, not only in the District of Columbia, but 
in lowa, Nebraska, and Missouri, as specimens were simultaneously 
sent to the agents of the Division in those States.¢ It has become 
so widely distributed since then as to lead to the inference that 
it must have been previously introduced at some other points, though 
the spread of an introduced species, even when introduced at a single 
point, is often so rapid that it surprises us, especially of a species 
that is winged, as evidenced by the spread of the Horn Fly (Hamato- 
bia serrata) over the whole eastern United States in about four years. 
Later, in 1891, with the aid of Mr. Fred. Enock, of London, a success- 
ful effort was made to introduce into this country from England an 
important Chalcid parasite of the Hessian Fly, Entedon epigonus Walker 
(Semiotellus nigripes Lind.). The details of this experiment will be 
*Third Rep., Ins. Mo., 1870, p. 29; Fifth Rep., do., 1873, p. 90. 
tSixth Report, Ins. Mo., 1874, p. 55. 
t Report of the Etomologist in Rep. U. 8. Dept. Agric. for 1884, p. 323. 
