op the SLUG WORM. 13 



free range procured for the faws, by fmal! teeth placed 

 on the outer fide of each; fo that while their vertical ef- 

 fect is that of a faw, their lateral effect is that of a rafp. 

 In the artificial faw the teeth all point outward and are 

 fimple ; but in the faw of the Tenthredo, they point in- 

 ward or towards the handle, and their outer edge is be- 

 fet with fmaller teeth which point outward. Some idea 

 ofthefawas connected with its back may be formed 

 from fig, 12, and of the faw alone from fig. 13. The 

 lateral teeth in the faw of the Slug fly are very minute, and 

 the want of light, when the greateft magnifiers are ufed to 

 examine a flat furface, has prevented my feeing them fuf- 

 ficiently well defined, to be able to exprefs them accurate- 

 ly, though the contour of the object is very diftinct, but 

 viewed edgeways they are plainly feen. I have there- 

 fore given fig, 14. of one from another fpecies inhabiting 

 the cherry-tree, which fhews this part of the ftructure very 

 plainly. 



I know not how long the flies continue to live after 

 their frrft appearace; though plenty about the trees, in 

 the time of depofiting their eggs, they become, afterwards, 

 very fcarce. I am equally uncertain as to the number of 

 eggs from a fingle fly. If all in the ovaria come to per- 

 fection, a fingle fly may depofit between two and three 

 hundred; but probably not more than half thefe are ex- 

 cluded by the fly. The ovaria are compofed of feveral 

 tubes, about fix on each fide, which occupy a great pari 

 of the abdomen, flowing from a common point, enlarging 

 in their courfe and uniting again on each fide, in a canal 

 leading to the oviduct, {fee fig* 15-) The eggs in thefe 

 tubes are of all intermediate magnitudes, from a fcarce 

 vifible fpeck to thofe ready to be excluded, of which la(i 

 I have frequently counted fifty, though the feafon of de- 

 pofiting was advanced. 



The flies do not feed like mod infects of this clafs, 

 on the honey of flowers; but upon the moillure which 

 they lick up from the leaves, moid with dew or fhowers. 



The vifcous coat of the Slugs feems to be their fuffi- 

 cient defence in the larva ftate; they are not, however, 



without 



