20 



THE AMERICAN ENTOMOLOGIST. 



hand the old school of philosophers, who believe 

 that every species was iudepeudently created, 

 will argue that this is so, in order to " complete 

 the System of Nature," and " carry out the Plan 

 of the Creation," and " give full aud free expres- 

 sion to tlic Thoughts of the Creator." Possibly 

 this may be the true solution of tlic difficulty ; 

 but— aud we say it in no irreverent spirit— what 

 should wc think of a Potter, who made all his 

 teacups without exception with handles ; those 

 for which handles were required with complete 

 ones such as you could put your finger through, 

 and such cups as were not wanted to have any 

 handles at all, with solid unperforated ones, 

 such as would be nearly useless? And what 

 should we say, if the Potter's friends were to 

 gravely argue, that he took all this unnecessary 

 trouble in order "to complete the System of 

 Art," and "carry out the Plan of the Tea- 

 drinker," and " give full and free expression to 

 the Thoughts of the Potter'"? 



The Native Currant Worm. 

 (Pn'stij)7iOia grossularioi, Walsh.) 

 Like the Imported Currant "Worm, this worm 

 produces a Sawfly, which, however, belongs to 

 a ditfercnt genus (Pristiphora), chiefly distin- 

 guishable from the other one (JVematus) by the 

 front wing lacking what is technically termed 

 the "first submarginal cross-vein." In Figure 

 11, b, we give a magnified drawing of the female 

 of this fly, and if the reader will look at this 

 drawing and compare it with that of the Imported 



IFig. 11.] 



('i)lors— (n) green and black; (i) black and honey-yellow. 



Currant Worm Fly (Fig. 7, a and />), ho will 

 see that there is in each of them but one cell, or 

 " pane " as it might be termed, on the upper 

 edge of the front wing towards its tip. This is 

 technically called "the marginal (or radial) 

 cell." Now let the reader look a second time 

 at these two figures, and he will see that, under- 

 neath this " marginal cell," there is a tier of 

 four cells in the one genus (Wematus) and a tier 

 of only three cells in the other genus (Pristi- 

 phora), the first or basal cross-vein being absent 

 or "obsolete" in the latter, so as to leave the 



first or basal cell extravagantly large. These 

 three or four cells, as they underlie the "mar- 

 ginal cell," are technically known as "the 

 submarginal (or cubital) cells;" and upon the 

 difference in the number and arrangement of 

 these marginal and submarginal cells depends 

 to a considerable extent the generic classifica- 

 tion of the Sawflies. For example, in another 

 genus {Euura) , v/\A<ih is closely allied to tlie 

 two of which we present drawings, there are, 

 as in the second of these two, one marginal and 

 three submarginal cells; but here it is the sec- 

 ond, not iha first (or basal) submarginal cross- 

 vein that is obsolete; so that here it is the 

 second, not the first (or basal) submarginal cell 

 that is extravagantly large, being formed in this 

 last case by throwing the typical second and 

 third cells into one, and in the other case by 

 throwing the typical first and second cells into 

 one, just as by removing the folding doors two 

 rooms are thrown into one. 



Persons who are not familiar with this sub- 

 ject are apt to suppose, that the pattern of the 

 curious network on every fly's wing varies 

 indefinitely in different individuals belonging 

 to the same species. As a general rule, there 

 is scarcely any variation at all in this matter, 

 each species and even each genus having its 

 peculiar pattern, and all the individuals belong- 

 ing to a particular species having the network 

 of their wings as exactly similar as the difl'erent 

 photographs executed by a Daguerreotypist from 

 the same negative plate. You may take, for 

 instance, a thousand honey-bees, aud you will 

 find that in the front wing of every one of them 

 there are exactly one marginal and three sub- 

 marginal cells, which however are all of them 

 shaped vei'y diff'erently from the corresponding 

 cells in any Sawfly, though all the thousand 

 honey-bees will be found to have them shaped 

 exactly alike, cell corresponding to cell, as in 

 any particular issue of i|.") Bank notes, vignette 

 corresponds to vignette and medallion die to 

 medallion die. Among the Sawflies, indeed, 

 as was noticed in the description of the Im- 

 ported Currant Worm Fly, the pattern of the 

 wing-veins in difi"erent specimens of the same 

 species varies occasionally a little ; but this is 

 the exception and not the rule, and is philoso- 

 phically of high interest, as showing how one 

 genus may in the course of indefinite ages change 

 gradually into another genus. 



The Native Currant "Worm Fly difl"ers in an- 

 other remarkable point from the Imported Cur- 

 rant Worm Fly. The sexes are here almost 

 exactly alike in their coloration, and with the 

 exception of the legs of the male beiug a little 



