280 Note on the TacJiivida% h/ Francis Walker. 



lias a hidden existence. Their migration therefore could 

 not have preceded, and most probably succeeded that of the 

 Lepidoptera. The opinions lately published that the cha- 

 racter of an insect is modified or established by the par- 

 ticular kind of insect in which it lives may be useful as 

 leading to more investigation of the parasitic flies -here 

 noticed. Is each kind of Tachinid generally constant in 

 its parasitism to one kind of Lepidoptera, and if it infects 

 two or more kinds are there two or more races, and are suc- 

 cessive generations of one race constant to one Lepidopter- 

 ous kind for sustenance ? If there be a transition from one 

 kind of maintenance to another does the change modify the 

 characters, and does the modification, as has been asserted, 

 become cumulative. Is its instinct in choosing a habitation 

 for its successors derived from its having had the same kind 

 of habitation, and supposing that it can have no access to 

 this hal)itation, is another dwelling place to which its 

 instinct leads it similar to that which one of its earlier 

 ancestors inhabited, and will its descendants follow its 

 example and select, if opportunity should occur, for the 

 next generation the kind of home in which they were main- 

 tained, or, in other words, what are the manifestations of 

 " the law of inheritance " as it is termed ? It is M^ell known 

 that the species of this tribe are very numerous and that 

 many of them rarely occur, and that the parasitism of most 

 of them is unknown. In the following list the names of 

 some Euro]3ean Tachinidas and those of their feeders are 

 placed side by side. It will be seen that by far the greater 

 part feed on Le])idoptera, but some kinds are parasites of 

 Coleoptera and Hymenoptera or of other Diptera, and one 

 kind is said to destroy Plusia gamma and Procrustes 

 coriaceus. 



Ocyptera bicolor, Oliv. - - Pentatoma grisea. 



Echinomyia grossa, L. - - Lasiocampa Trifolii. 



„ fora, L. - - - Lithosia quadra, Arctia 



auliea,Lymantriamonacha, 

 and Trachea pinij)erda. 



Gymnochfcta, viridis, Fall. - Miana arcuosa. 



I'lagia trepida, Meuj. - - - Lophyrus Pini. 



Cionia flaviceps, Zett. - - - Hadena glauca. 



Nemora'ca glabrata, Met)/. - Trachea piniperda. 

 „ rudis, Fall. - - „ „ 



