136 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 prejing upon and devouring it^ for 

 each iiind of aphis from which I have reared these insects has 

 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 veiiis, and these commonly end 

 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 thestalksof lettuce 

 in our gardens. This in my manuscripts is named 



The Lettdoe-loiise Aphid ms (.-4. Lactucaphh) , It is deep black with tegs tinged 

 ■with brownish, their bases and Itnees very slightly paler; the abdomen long obovate, 

 flattened, rather narrower thau the thorax, its apex roundedj'antennse almost as 

 long as the body, 19-jointed, second joint smallest, globular, 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 whit'e. 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), 

 and may be named 



The Knot-weed Aphidius (Praon Polygonaphii). It is black and 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 anterior sutures, its base 

 being narrowed into a short cylindrical pedicel, which witli the legs and bases of the 

 antennae are of a bright reddish or beeswax yellow color, the tips of the feet being 

 tlack; its antennaj 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, tlie last rather 

 longer thau the preceding, its apex abruptly rounded. Length 0.08, wiLgs ex- 

 pand 0.15. 



Another species is a common destroyer of a species of aphis 

 ■which Infests the fruit stems of the high cranberry, {Viburnum 



