480 Ebport op the Entomologists of the 



laid singly on the tips of stiff stalks of silk which are 

 fastened to the leaf in an upright position. The stalks are 

 about half an inch high. When full grown the larva rolls itself 

 into a little ball of white silk from which the mature insect finally 

 emerges. These voracious larvae suck the juices from their vic- 

 tims, holding the plant louse or other prey at the tips of their 

 long jaws and sucking the liquid by mean® of their peculiarly 

 arranged mouth parts. A drawing of one of these larvae, greatly 

 enlarged, is shown at Plate XXVI, fig. 12. When about full 

 grown a larva of this species measures about 4.4 mm. 



Parasitic Insects. 



The work of these little insects was much more apparent upon 

 the currant plant lice than upon those under observation on the 

 plum trees. No parasites were reared from the latter. 



Aphidius polt/gonapJiia* Fitch. — This minute insect belongs to 

 a large group of beneficial insects which are classified in the same 

 order with the wild and tame bees, namely, the Eymenoptera. 

 This parasite seems to have a special liking for the currant plant 

 louse, Myzus ribis, although it is a common parasite on other 

 species. The egg of the parasite is laid on or just under the skin 

 of the plant louse, and when this is once done the unfortunate 

 louse is doomed. The egg soon hatches and the, minute larva 

 feeds upon the tissue just beneath the skin, taking care at first 

 not to touch a vital organ. By the time it has become full grown, 

 however, nothing remains of the host but the integument. The 

 larva transforms to the pupa within its host, the mature insect 

 cutting its way out. A parasitized plant louse soon becomes in- 

 active, and swells up until it is somewhat larger than the largest 

 of its fellows. The integument becomes hard, finally almost 

 brittle, and turns pearly white. At Plate XXVI, fig. 1, some of the 

 parasitized lice are shown on the under surface of a currant leaf. 



Although present during the entire time that the plant lice 

 were common upon the currant, they were especially abundant 



♦Identified by Mr. WiUiam Ashmead. 



