174 



this species are figured and described by Snellen van Vollenlioven in 

 Tijc^chrift voor Entomologie (IV, 18G0, pages 176, 177, plate 12). The 

 ovipositor of the pupa, as is to be expected, is only about one-half as 

 long as that of Thalessa. 



Probably" as good an account of the method of the boring as has been 

 published, and one of the earliest accurate accouuts, is that contributed 

 by Mr. J. Quay to our American Entomologist for September, 1880 (Vol. 

 Ill, page 219). We quote from this article as follows: 



As these insects, by standing on "tip-toe" and elevating their abdomen to its fullest 

 height, can clear but about 2 inches space, the problem presents itself as to how can 

 the remaining 3 inches of ovipositor be disposed of in order to allow the drill end to 

 enter the perforated stump. 



I observed that after raising the abdomen as far as possible the drill was worked 

 forward so as to slightly bend under, giving the insect a purchase on same. Then 

 followed a bearing-down motion on the bent tube, curving the end of the abdomen for- 

 ward and upward, and next forcing the ovipositor, near its attached end, to curve also 

 and pass up through the abdomen and above into a cavity which there opened for 

 its reception. 

 What a strange provision of Bfature ! 



The cavity was inclosed by a membranous sack, capable of great distension, and 

 while the drill was being continually forced up through, it curled about within the 

 sack, forming one complete bend of about three-fourths of an inch in diameter, and an- 

 other partial one. When fully distended the sack was very thin, quite transparent, and 

 seemingly upon the point of bursting apart. But the ovipositor was in this manner 



brought to the edge of the worm-hole, 

 was slipped in, and thus made to ease 

 away upon the distended sack, which, 

 by collapsing, forced out again the drill 

 by its mere force of contraction. The 

 coil now soon disappeared, and the in- 

 sect was fully prepared to commence op- 

 erations upon the hapless Tremex. 



STRUCTURE OF THE OVIPOSITOR. 



Our readers who have followed 

 us so far will doubtless wonder 

 how an eg^ can be passed down 

 such a long ovipositor not wider 

 than a horse-hair. A careful ex- 

 amination will show that this in- 

 strument is composed of three 

 parts, which may, upon being soft- 

 ened, easily separate, but which 

 in nature are securely locked to- 

 gether. Figure 38 illustrates the 

 ends of these three parts a, a, h as they appear when on their flat sides? 

 and it will be noticed that the tips are strongly notched diagonally, 

 which structure facilitates the insertion or boring into the tree and 

 renders extraction somewhat more difficult, especially where the wood 

 is somewhat hard. Now ths dorsal or central piece is solid at its 



Fig. 38. — Ovipositor and egg of Thalessa; a, b, a, 

 tips of component parts of ovipositor proper; c, 

 cross-section of ovipositor; d, egg; e, e, ventral 

 pieces of ovipositor proper; /, middle or dor.sal 

 piece of ovipositor, all greatly enlarged (original). 



