138 CHERRY. LEAVES — APHIDIUS SPECIES. 



every kind of tree and plant appears to have one or more species 

 of aphis infesting and blighting it, each species of aphis seems to 

 have a particular parasite preying upon and devouring it; for 

 each kind of aphis from which I have reared these insects hag 

 furnished a species differing from all the others, and in some in- 

 stances two species have been obtained from one kind of aphis. 

 The British entomologists enumerate upwards of fifty species of 

 these insects, which is nearly equal to the number of their aphides. 

 They differ from all the other insects of the family to which they 

 pertain, by having commonly a very large triangular stigma to 

 the fore wings, and very few veins, and these commonly enct 

 abruptly without reaching the apical or inner margins. Hence 

 there are but few if any closed cells or panes to the wings. One 

 of our species having the wings more fully veined and forming 

 complete cells may be met with accompanying what appears to be 

 an undescribed species of aphis which infests the stalks of lettuce 

 in our gardens. This in my manuscripts is named 



The Lettuce-louse Aphidttts {A. Lactucapkis} . It is deep black with legs- 

 tinged with brownish, their bases and knees very slightly palar ; the abdomen 

 long obovate, flattened, rather narrower than the thorax, its apex rounded j 

 antennae almost as long as the body, 19-jointed, second joint smallest, globu- 

 lar, third joint longest with a slight constriction in its middle, the succeeding 

 joints successively shorter, the last scarcely longer than the preceding one, 

 long ovate; wings slightly smoky, outer marginal vein and the vein bordering 

 the cell beyond the stigma black, the outer veins brown, stigma dusky white. 

 Length 0.06 to the tip of the abdomen. 



One of the prettiest species which I have met with was bred 

 from aphides upon the spotted knot-weed {Polygonum persicaria) 7 

 and may be named 



The Knot-weed Aphiditts (Praon Polygonaphis), It is black und shining 

 with a slender elliptical abdomen of a bright sulphur-yellow color tinged with 

 dusky above and at its tip beneath, with broad clear yellow bands at the an- 

 terior sutures, its base being narrowed into a short cylindrical pedicel, which 

 with the legs and bases of the antennae are of a bright reddish or beeswax 

 yellow color, the tips of .the feet being black; its antennae are inserted on 

 slight broad elevations upon the front of the head and are 17-jointed, the two 

 short basal joints being a third thicker than the following ones, which are 

 equal, cylindric, four times as long as they are thick, the last rather longer 

 than the preceding, its apex abruptly rounded. Length 0.08, wings expand 

 0.15. 



Another species is a common destroyer of a species of aphis 

 which infests the fruit stems of the high cranberry, {Viburnum 



