INSECTS AFFECTING PARK AND WOODLAND TREES 2>37 



Say may be instantly recognized by the distal niaaMn of the liiml tibia beinif 

 thickly set with stout, chitinous processes. 



rhe structure of the so called t^izzard or |)ro\eiUriculus is eNceedin_L(ly 

 interesting;- in this ,L;rou[), most of the species differing!: markedl)- in this 

 respect from their allies. The employment of this ori^-an in systematic work 

 is not new. It has been used by myrmecoloijists and Dr J. P>. Smith, in a 

 report issued a few years ai^o, calls attention to the fact that various species 

 of kat\ilids present recoonizable differences in this organ. The structure 

 of the Scohtid proventriculus is eNceedin,s:,dy interesting. It consists of a 

 series of eight 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 cud 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 namedi the strainerlike hairs probably in the normal posi- 

 tion. There are several well marked types of proventriculi. 'fhat i)f 

 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 |)()sle- 

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

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

 edly serve as strainers as stated above. This type is also found in I'ityo- 

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

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

 which are numerous chitinous points placeil 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. .\ modification is seen in 

 the proventriculus of P hi o e o s i n u s d e n t a t u s Say | \)\. 69, fig. 4]. 

 Another type, intermediate i)erhaps between that of Tomicus and Dendroc- 

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

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

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

 structure composed apparenth- of fused entls 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 nicel>- shown on plate 68, figures 2, 3, 6 and 8, and plate 69. fj.g^nre 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 a u t o g r a p h u s Ratz., and I), e i c h h o f f i i 1 1 opk. [ [A. 69, tig. 

 9 and I rj also bring out this i)oint nicely, there being a marked difference in 

 the toothing of the anterior ])ortion of the plates. 



