THE JUMPING PLANT- LICE OR PSYLLID^ OF THE NEW WORLD. 25 



of hind Jegs with two black, claw-hke spines at end, as in Psylla 

 and many other genera. Wmgs elongate-ovate, never acute at 

 apex, often more or less thickened and subopaque or hyaline, often 

 maculated or spotted; M + Cu nearly always as long as R; pter- 

 ostigma always wanting. Male anal valve always with a long, 

 horizontal, posterior lobe, extending back to forceps. 



Type of genus. — Chermes caWise LinnaBus. Foerster erected this 

 genus in 1848, and named m it several species but indicated no type 

 species. 



Tlie structure of the head resembles rather closely that of Livia; 

 the vertex is flat, the frons similar in form, position, and appearance; 

 genge similar; antennae short; notum rather flat; pronotum some- 

 what similar. In the hemispherical eyes, however, the two genera 

 are quite distinct. 



Since my treatment of this genus in a previous paper (Crawford 

 'lib: 492) a considerable amount of additional material has come to 

 hand, includmg several new species, and many new records for already 

 described species. Several new species have been added also by 

 Miss Patch (Patch '11: 16; '12b: 216-219), as well as some life- 

 history records. 



This genus presents serious difficulties to the systematist because 

 of the great amount of variation m certain characters which in other 

 genera are more or less constant. Size and color of body, shape of 

 forewing, presence, absence or degree of maculation or coloration of 

 latter, size of genital appendages in both sexes, are all subject to 

 considerable variation within a species, or else there are a very 

 large number of closely related and intergrading species. 



The collection of the United States National JMuseum contains a 

 very large number of specimens of this genus from many localities, 

 and with accompanying notes and data of varying degrees of com- 

 pleteness. Tliese specimens, together with those of the C. F. Baker 

 collection, have been divided into apparent species and arranged 

 in series of variation. In many cases the series are very long, and 

 the variations are so gradual and complex that it is quite impossible 

 to separate species within the series. Until accurate ecological 

 data is available for many of these species we can not be sure of our 

 systematic arrangement. All that can be done at present is to 

 group these series of similar forms into provisional species. Any 

 attempt to subdivide them wouJd result in confusion. 



SYNOPSIS OF SPEaES. 



a ^ Antennag ten-segmented. 

 6 K Clypeus much elongated, more or less cylindrical, rounded or truncate at apex, 

 extending down and forward; notum with four more or less distinct light- 

 colored stripes; female genital segment very short; wings hyaline to fumate, 

 or maculated apically .calthse Linnseus, 



