72 BIOLOGICAL SOCIETY OF WASHINGTON. 



The species, so far as known, are all gall-makers, and confined to 

 the Hackberry {Celfis). 



There is no genus, among those characterized by Dr. Fr. Low, with 

 which Pachypsylla can properly be compared. In the convexity of 

 the body it greatly surpasses Psylla, from which it is at once distm- 

 guished by the vertical and rugoso-punctate head, the quadrate ver- 

 tex, the short frontal cones, the less filiform and stout antennse. 



Pachypsylla venusta (Osten-Sacken.) 



Average length, 5.6 mm. General color, brownish-yellow, variegated with 

 darker brown, often with a greenish tinge, thorax with brown marlcings of the 

 usual shape, front wings whitish speckled with brown, legs variegated with black. 

 Head with the eyes narrower than the widest part of the thorax, vertical, slightly 

 ernarginate behind, vertex about one-third wider than long, nearly flat, not\ar- 

 rowing anteriorly, with anterior marginal line straight, slightly elevated along the 

 inner margin of the eyes, surface rugoso-punctate, discoidal impressions pulicti- 

 form, very distinct, median line fine ; frontal cones below the plane of the vertex, 

 vertical, very little longer than wide at base, rounded at tip and sides, not half as' 

 long as the vertex, and togetlier only half as wide as the vertex, moderately diver- 

 gent, rugoso punctate, sparsely pubescent, and in color often brighter yellow than 

 the vertex ; antennre as long as the head is wide, joint 2 a little longer than i , 

 joint 3 twice as narrow as 2 and but little longer than 4, the succeeding joints' 

 gradually decreasing in length, the terminal three closely conjointed, very little 

 thicker than the preceding joints ; each of the intermediate joints at tip a little 

 wider than the base of the following joint; color, pale yellow, tips of interme- 

 diate joints and the whole of the last two joints black ; terminal bristles very short. 

 Pronotum moderately short, of equal width, slightly emarginate behind, steeply 

 ascending posteriorly, sculptured and colored as the head ; lateral impressions 

 well marked. Dorsulum well developed, thrice as long as the pronotum and 

 about twice as wide as long; posterior lobe distinctly longer than the anterior; 

 hind margin sinuate each side and truncate at middle; surface finely alutaceous; 

 color, light brownish yellow, with a large brown apical spot divided by a yellow 

 median line. Mesonotum convex, wider than the head, sculptured as the dorsu- 

 lum, with four vittae (longitudinal) of brown or greenish-brown color, the outer 

 ones usually wider than the inner ones, all bordered and divided transversely by 

 lines of brighter yellow. Front wings two and one-third times longer than their 

 greatest breadth, widest at basal half, whitish, semi-transparent, "marked with 

 brown, as follows : an oblique and gradually-diminishing band running from the 

 tip of radial cell to middle of first furcal vein, more or less interrupted between, 

 but persistent on the veins ; a series of four large quadrate marginal spots at tips 

 of furcals, a spot at base of pterostigma ; paler specimens have these marks well 

 relieved on a uniformly semi-transparent wing, while darker specimens have them 

 more or less suffused with brown atoms, which often obscure the apical half of 

 the wing and gradually intensify towards the posterior margin, where they always 

 leave four clear, whitish terminal spaces between the veins, the fourth least distinct 

 and sometimes obsolete ; costal margin much rounded at base, thence straight, tip 

 very narrowly rounded, nearly angulated, inner margin at terminal third rounded. 

 Venation moderately strong, discoidal part of subcosta elevated into a prominent 

 callus, pterostigma distinct, moderately long; petiolus cubiti as long as the stem 

 of the first fork and one-half as long as the discoidal part of subcosta, which 

 is as long as, or a little longer than, the basal part ; radius nearly parallel to the stem 

 of second or outer fork and fourth furcal, slightly curved upward at tip, all fur- 



