4D4 W. WESCHE ON THE LIFE-HISTORY OF THE TACHINID FLY, 



destructive to crops, and harmful to various plants, and Phoro- 

 cera must be considered, from the economic point of view, a 

 useful, if cruel, insect. It is obvious that many caterpillars are 

 attacked by a single female, as one could scarcely carry ninety- 

 eight parasites. 



Another species (P. lata, Ztt.) has been bred from a saw-fly 

 (Lophyrus pini), and these insects are, like the moths and butter- 

 fly, destructive, as they greatly damage the pine forests.* 



The parasitism of Diptera on Hymenoptera is rare compared 

 with the constant attack of the Tachinidae on Lepidoptera. 



By means of the microscope it is possible to detect the vivi- 

 parous condition of flies, if the specimens are properly cleared 

 and prepared, as the hard chitinous jaws are not dissolved by 

 potash, and are very characteristic in appearance, showing 

 through the cleared plates of the abdomen. I have already 

 published my observations on four insects: Oliviera lateralis, F., 

 Plagia trepida, Mg., P. serriventris,^ and Phora rujicornis, Mg.,J 

 and I now add to that list Myioba fenestrata, Mg., and Siphona 

 geniculates, Deg. 



According to Schiner, the metamorphosis of Oliviera is tin- 

 known, and I am unacquainted with any later observations; I 

 counted over twenty-five jaws in my preparation (Fig. 4). 



The larvae of Plagia are parasitic on caterpillars, and have 

 also been found, like those of P. lata, on Lophyrus pini ; this 

 insect can also be ranked as beneficial to man, but its capacity 

 for usefulness is less, as I found under twenty jaws of larvae 

 in my preparation, a great contrast to the more prolific P. serri- 

 ventris (Fig. 7). 



Phora ruficornis is somewhat singular, as the large majority 

 of Phoridae lay eggs ; but it belongs to a family the species of 

 which are small in size, but great in numbers, and present many 

 curious features and anomalies in life-history. There are a 

 number of wingless species, and some are recorded as living in 



* Die Flicgen, vol. i. p. 489. 



t Jour. 11. Mie. Soe., 1908, p. 421. 



X Traits. Ent. Soc. Loud. 1908, Pt. II. p. 291. 



