46 



Moreover, I have observed that in a state of nature but a comparatively small 

 proportion arrive at matiuity, which to some extent accounts for its rarity. I 

 have never observed any indications of autumnal specimens. 



Scolytus Pruni, Ratz. is the scarcest of the species I have observed. Super. 

 ficiaUy it much resembles Scoli/tus Destructor, but is rather smaller and much 

 more shining, especially as to its elytra which are sometimes nearly black. The 

 thorax is less strongly punctated, and the elytral puncta are disposed in uni- 

 formly faint strisj. I have met with this beetle in apple and pear, and have 

 found its abandoned burrows in apricot. It is said to affect various fruit 

 trees. The apple trees in which I have found it had been slowly dying, 

 successive strips of the bark from top to bottom of the tree had died year after 

 year, and it was in the last strip that Prtmi had burrowed, and completed the 

 death of the tree. I have met with traces of its having more sparingly attacked 

 the previous strips. A specimen I show you is a portion from one of these trees. 

 Unhke the other species of the genus, which make nearly uniformly cylindrical 

 burrows (there is often a trace of a diverticulum near the entrance of Destructor's 

 burrow), the first part of the bui-row of Scohitus Pruni is a nearly square 

 chamber, as if two burrows had for so far been placed side by side. I have 

 foundjthe male beetle in this cavity in burrows little more than begun, and in 

 others nearly two inches long, and have no doubt that it is formed by the male 

 beetle, who eats the removed material as food ; in none of the other species have 

 I found the male residing in the burrow for more than a very brief period. The 

 remainder of the burrow is from two to four inches long, and slightly encroaches 

 on the wood. The eggs are covered by a layer of fine frass, which usually 

 forms merely a series of detaclied patches filling up the egg cavities to the level 

 of the wall of the gallery. The larvaj almost invariably bury themselves in the 

 wood for hibernation, and the beetles do not emerge till spring. They are the 

 last of the genus to appear, and are only now (June 25) coming out, whilst 

 Destructor has been out for several weeks. This species is by no means hardy, 

 for a large proportion of the broods die, but it is not so delicate as S. muHistri- 

 atus, 



Scolytus ruguhsus, Ratz. is the smallest of the genus. Its elytral striaj 

 are so marked, and run into each other so freely, that the elytra might rather be 

 called shagreened than punctated. Like Pruni, it feeds on fruit trees, and espe- 

 cially on apple. Though hitherto accounted rather rare, it must always be 

 commoner than Scolytus Pruni, because it is a much hardier species, and whilst 

 Scolytus Pruni prefers large trunks, and does not enter wood smaller than 

 thiee inches in diameter Scolytus rugulosus burrows in all, even in branches 

 which are mere twigs, and so finds abundant pabulum, where Scolytus Pruni 

 would starve. I have never detected rugulosus in the living tree, and do not 

 believe that either it or Scolytus Pruni is injurious to orchards. It comes out 

 about a week before Pruni, but later than the other species of the genus. It 

 is coming out abundantly at present (June 25), whereas Pruni is only beginning 

 to emerge, and the other species are now fully engaged in ovipositing. This insect 



