OAK-BORERS. 55 



through it, so as to carry the egg beyoud the hair-like scales with which the body is 

 clothed, some of these touching adhere to it, their attachment to the body being so 

 slight. 



The eggs are of a broad oval form, and about half the size of a grain of wheat, be- 

 ing the tenth of an inch in length and three-fourths as thick, of a dirty whitish color 

 with one of the ends black. When highly magnified their surface is seen to be retic- 

 ulated or occupied by numerous slightly impressed dots arranged in rows like the 

 meshes in a net. From the fact that several worms of the same size are sometimes 

 met with in a single tree, indicating them all to be the progeny of one parent, it ap- 

 pears that the female drops a number of eggs upon each tree that she visits, and prob- 

 ably disposes of her whole supply upon a very few trees. The size of the eggs doubt- 

 less renders them a favorite article of food to some of our smaller birds. And a bird 

 in discovering some of these eggs will be incited thereby to search for others in the 

 same vicinity, which search being successful, will be perseveringly continued so long 

 as an egg can be found upon that or any of the adjacent trees. Thus it may be that 

 of the whole stock of eggs which a female deposits, scarcely one escapes being picked 

 up and devoured. This appears the most probable cause of so few of these worms 

 being met with, although the females are so prolific. 



The worm on hatching from the egg sinks itself inward and feeds at first on the soft 

 inner bark, till its jaws acquiring more strength it penetrates to the harder sap-wood 

 and finally resorts to the solid heart-wood, residing mostly in and around the center 

 of the trunk, boring the wood here usually in a longitudinal direction, and moving 

 backwards and forth in its burrow, enlarging it by gnawing its walls as it increases 

 in size, whereby the excavation comes to present nearly the same diameter through 

 its whole length. In an oak in which I met with two worms fully grown aud several 

 others but half grown, the whole of the central part of the trunk had been exten- 

 sively mined by preceding generations of this insect and was in a state of incipient 

 decay ; and I thus had an opportunity to notice the fact that none of the worms were 

 lying in the decaying wood, all being outside of this, where the wood was still sound. 

 Hence it is evident that it is living healthy trees which this insect prefers, and not. 

 those which are sickly and decaying, which latter are preferred by the European 

 Cossus, some authors say, though perhaps their observations have not been exact upon 

 this point, for in the instance here alluded to it would have been said on a first glance 

 that these worms preferred decaying wood, since the diseased heart of the tree was 

 everywhere traversed with their burrows, and the sound wood showed few of them; 

 and thus no doubt in many other cases we mistake the cause for the effect, and on 

 seeing semi-putrid wood filled with worm-holes, we suppose the worms have preferred 

 wood of this character, when in truth it is these holes which have caused the decay 

 of the wood. 



These worms are probably three years in obtaining their growth. They cast off 

 their skin several times, and after the last of these moltings their color becomes 

 different from what it has previously been. 



The larva previous to the last change of its skin is of a rose-red or a pale cherry- 

 red color, often with a famt jellowish stripe along the middle of its back, on all 

 except the three anterior rings. It is of a cylindrical form, slightly broadest ante- 

 riorly and a little flattened beneath. It is divided by transverse constrictions resem- 

 bling broad shallow grooves into twelve rings, which are twice as broad as long. On 

 each of these rings are a few pijfiples of a deep purple color, regularly placed, each 

 giving out a pale-brown bristle. Four of these pimples are on the back, placed at the 

 angles of an imaginary square or a trapezoid having its hind side the longest, the two 

 hinder pimples being larger. Small white dots confluent into broken lines may also 

 be perceived, forming a transverse square in which the two anterior pimples are 

 inclosed, and other dots less regularly placed surrounding the two hind pimples 

 except upon their hind side. Above the breathing pores on each side is also a large 

 pimple, which, upon the four rings bearing the prolegs, has a white dot in its lower 

 «dge, which dot does not appear in the corresponding pimples of the other rings. A 



