INSECTS AFFECTING PARK AND WOODLAND TREES 337 



Say maybe instantly recognized by the distal margin of the liind tibia being 

 thickly set with stout, chitinous processes. 



The structure of the so called gizzard or proventriculus is exceedingly 

 interesting in this group, most of the species differing markedly in this 

 respect from their allies. The employment of this organ in systematic work 

 is not new. It has been used by myrmecologists and Dr J. B. Smith, in a 

 report issued a few years ago, calls attention to the fact that various species 

 of katydids present recognizable differences in this organ. The structure 

 of the Scolytid proventriculus is exceedingly interesting. It consists of a 

 series of eig'ht double, rectangular plates, the posterior extremities of which 

 are provided with a series of long, chitinous, hairlike processes, undoubtedly 

 serving as strainers to prevent the entry into the true or chyle stomach, of 

 untriturated material. An end view of this organ is given on plate 68, 

 figure I, and plate 69, figures 2, 5, each of which shows the octagonal struc- 

 ture and the first named, the strainerlike hairs probably in the normal posi- 

 tion. There are several well marked types of proventriculi. That of 

 Tomicus, shown on plate 68, illustrates a highly developed form in which 

 the anterior portion consists of a series of plain, chitinous basal plates inter- 

 locked more or less perfectly by a series of marginal teeth, while the poste- 

 rior part is narrower, strongly ribbed with chitinous bars and in addition, 

 provided with a series of long, slender, chitinous processes, which undoubt- 

 edly serve as strainers as stated above. This type is also found in Pityo- 

 genes and Dryocoetes. Dendroctonus [pi. 68, fig. 7] has a simpler form of 

 proventriculus, consisting of a series of eight double plates, in the walls of 

 which are numerous chitinous points placed in more or less irregular rows. 

 The posterior portion is provided with a series of stout, chitinous rods which 

 terminate at the free margin in tufted processes and long, slender, chitinous 

 rods, which latter evidently serve as strainers. A modification is seen in 

 the proventriculus of Phloeosinus dentatus Say [pi. 69, fig. 4]. 

 Another type, intermediate perhaps between that of Tomicus and Dendroc- 

 tonus or Phloeosinus, is found in Xyleborus, Xyloterus and some other 

 genera. It consists of the usual double plates, each provided along its 

 length with a series of stout, chitinous bars terminating in a stout, dense 

 structure composed apparently of fused ends and at the posterior extremity 

 there are a number of long, slender, chitinous processes which unite to form 

 a strainer. The differences in this organ between closely allied forms, are 

 very nicely shown on plate 68, figures 2, 3, 6 and 8, and plate 69, figure 10, 

 which illustrate portions of the proventriculus of certain species of Tomicus. 

 It will be seen that no two are alike, though all present a general resem- 

 blance one to another. The illustrations of the proventriculus of Dryo- 

 coetes au t ogr ap h u s Ratz., and D. eichhoffii Hopk. [pi. 6g, fig. 

 9 and 1 1] also bring out this point nicely, there being a marked difference in 

 the toothing of the anterior portion of the plates. 



