January, 1912.] 



37 



Plant Sanitation. 



with inch spaces between the crates to 

 keep the potatoes ventilated and dried 

 out. One inch strips of board may be 

 placed on each tier of crates to give 

 ventilating space between tiers. In 

 pitting in the field, a dry position should 

 be selected, so as to avoid surface water. 

 Potatoes may be piled in a conical heap 

 or in a long rick. The heap or rick 



should not be more than 4 feet wide on 

 the ground and 2 feet high. Potatoes 

 may be then covered with straw, and 

 just enough soil added from time to 

 time to keep them from frosting. 

 Ample ventilation should be left ftt the 

 top of the pile, however, for all steam 

 and heat to escape and to prevent 

 sweating or heating of the potatoes. 



PLANT SANITATION. 



" SHOT-HOLE BORERS" (SCOLY- 

 TIDjE AND BOSTRICHIDjE). 



By E. Ernest Green, 

 Government Entomologist. 



These two families of beetles, though 

 somewhat widely separated in the 

 systematic arrangement of the Goleop- 

 tera, are remarkably similar in external 

 appearance. They have the same cylind- 

 rical form, the head more or less 

 concealed beneath the thorax, and many 

 species of both families are curiously 

 truncate behind, this formation being 

 effective in blocking the entrance to the 

 tunnel when the insect (as ic often does) 

 is resting at the mouth of its gallery. 

 The resemblance between Scolytidce 

 and the smaller members of the Bostri- 

 chidce is so close that a microscope is 

 often necessary to determine whether 



The term " Shot-hole 

 Borer " has been generally 

 restricted, in Ceylon, to a 

 single species (Xyleborus 

 fornicatus) that infests the 

 living tea bush. But there 

 are actually very many 

 species, by far the greater 

 number of which confine 

 their attentions to wood 

 that is either dead or 

 diseased. The insect that 

 riddles cut bamboos and 

 bamboo baskets is a small 

 Bostrichid (Dinoderus min- 

 utua). Other Bostrichids 

 attack dry wood — especi- 

 ally immature or badly 

 seasoned timber, and some- 

 times reduce it to a mass of 

 powder. Both Bostrichidcm 

 and Scolytidce are strongly 

 attracted by bark and wood that has 

 been infected by canker and other fung- 

 al diseases. When Cacao canker first 

 attracted attention in Ceylon, the pre- 

 valence of small boring beetles in the 

 diseased areas of the bark led to a mis- 

 conception of the origin ot the disease. 



any particular individual belongs to one 

 or the other family. Itisprobale that 

 this similarity is not indicative of any 

 common ancestry (of comparatively 

 recent date), but that it is the result of 

 convergence due to identity of habits 

 and of structural requirements. 



The principal distinguishing character 

 between the two families is in the shape 

 of the antennae, the terminal joints of 

 which, in the Scolytidce, are compressed 

 and expanded into a flattened club (fig. 

 a), while in the Bostrichidce these joints 

 are distinct and more or less serrate 

 (fig. b.) There is also an essential 

 difference in the feet, Scolytidce having 

 4-jointed and Bostrichidce 5-jointed tarsi. 

 In the early stages the larvse may be 

 readily distinguished by the presence of 

 well-developed legs in the young Bostii- 

 chids, the Scolytid grubs being quite 

 apodous. 



Antennae of Bostrichidse and Scolytidos. 



It was, not unnaturally, presumed by the 

 cacao planters that the injury to their 

 trees was caused by an insect enemy. It 

 was only after scientific investigation 

 that the true nature of the disease was 

 determined. A similar misconception 

 is now arising in the case of Etevea 



