330 



THE AMERICAN 



barley, by Dr. Harris aiicl Dr. Fiteh. Dr. Harris was of 

 opinion that they were all varieties of one ancT the same 

 species; but Dr. Fitch, basing; his opinion chielly upon a 

 slij^ht diilerence in the coloration of the legs, lias made four 

 (.lifferent species of I hem, which he separates as follows {N.Y. 

 Rep. in, p. 154): 

 Eurytomo. trltici. Fitch —Oi 

 Eurytoma aeealis, ritcli.--0 

 Eui'ytomaliordei, Harris.— ( 

 Eux-ytoma fulvipes, FitL-h.— 



■.vheat. Front tibim iltil 





vollou 



■ n 



die and hi 



k1 tibi;v) bific'k 









rvo. Fro 



ntandliindtil) 





•HI 



iliddlc til) 

 n l.arlc-v. 



.•vl)lacl< 



rtiKs 



omr d 



•iki 



ilai;l<isl, c 



>]or\vitlitlion 



(Idle 



iidliii 



h. 



Dn l.orln 



Logs, iacll 



dii.K 



all U.i. 



tri 



My experience runs mtiruly cu 

 such colorationul iHsl.inf.tlnns !.h 

 species. I brctl and preserved 'S.l 

 barh'}'-;^-alls, and 1 found, that 



y yeilo 



ih'i' 1(1 l]\ii existence of any 

 :yvt-[\ these four so-called 

 5- and 47 Q from Canadian 

 iin«t of tliem were fritici 



Fitch, two were secalis Fitch, a few verged upon liordei 

 Harris, and seven verged u])ou/«/:iiy>(?s Fitch; and that num- 

 erous intermediate grailes occurred between all these four 

 forms. Therefore, I incline to believe that Fitch's three 

 so-calie<I species are — so far as the facts indicate— mere 

 synonyms of hordei Harris; and that the correct name lor all 

 the Joint- worm Flius that infest small grain is Jsosoma hordei, 

 Harris. As the reader will at once perceive, from the de- 

 scriptions of the diflercnt siiecies oi Enrijtoina anil Decatoma 

 given above, if I had regarded slight difterenccs in the color- 

 ation of the legs as of specilic vahie, I sliould have made 

 several hundred new species where I now make only about a 

 dozen . 



[Fi, 



I give herewith lignves (Fig. 3 and Fig. 4) of Jsosoma hordci 

 (f 9 1 drawn by Mr. Uiley from specimens In-ed from Canadian 

 barley-galls. It is not necessary to describe the species, as 

 tills has already been done in a vci'y full manner by Fitch. 

 (N. Y. Rp.j). Ill, pp. 1G2-3.) 



I do not deny the ])0ssibility of the Joint-worms infesting 

 resiiectively wheat, rye and barley being what I have called 

 '*pliytophugic species." (Sec Pror, Ent. Soc.Phil. Ill, pp. 

 403-4:J0, and V, pp. 104—316.) IJut, before I believe in such 

 a fact, I require some satisfactory i)roof of it, wliicli has 

 never yet been given If they iin- so, then the Hies that have 

 bred in a particular wlieat Held can never infest an ailjoining 

 barley lieh.l, and so on. So far as the recorded facts go, they 

 point directly iu the Ojjposite dirrclion. Dr. Fitch, for ex- 

 ample, allows that he liiinsel f found :i,S ^^^d several 9 , which 

 he identified as being AonZei, on the growing rye of a i-ye field 

 at the end of May and beginning of June. {N. Y. Rep. Ill, 

 p. ir)9.) Now, if these insects did not intend to attack the 

 rye, what business could they have there ? 



I am well aware th:\t, with most entomologists, the mere 

 proof of the fact that two imagos cannot be distinguished in 

 the cabinet is sullicient to estalilish their specilic identity. 

 For myself, I hold very diilerent opinions. I consider the 

 orUiuary determinations of species by the mere comparison 



of a few cabinet specimens of the imago to be only provisional 

 — a kind of entomological make-shift till we can arrive at 

 something more definite and satisfactory. To approximate 

 to a correct knowledge of specific limitations we must go out 

 into the woods and the fields, and study insects, not only in 

 tlie imago state but in all their states, from the egg to the 

 mature form. Wl* nuist attend to habits, as well as to exter- 

 nal structure; IVir it may — and I believe does— frequently 

 hapiiL-n tliat, allhongli the external structure and the colora- 

 tion <.)f two forms be aljsolutel^'' undistinguisliable, yet that 

 tln'ii- internal structure may diller so wi<lely that their habits 

 may l)e invariably very diUerunt, and the two must couse- 

 quuntly, if constant dilference of structm-e makes difference 

 of species, belong to two distinct species. 



"We have a notable example of such a contingency in two 



vernal forms of Cijnvps — C. q spongi/ica^ O. S., and C. q in- 



anis, O. S.— which infest distinct oaks, produce quite dis- 



LFig. 5.] 



tinct galls, and of one of which there is an autumnal j 

 dimorphous Q'—C. q. aciculata — while of the otlier species 

 (C q. inanis) I am as certain as I can be of any negative fact 

 that no such dimorphous 9 exists. Yet the cabinet speci- 

 mens of the tw^o vernal types cannot be distinguished; and 

 any closet naturalist who received a hundred of e:iehof them 

 would infallibly pronounce them to be all identical. But 

 that there must exist internal structural difterenccs between 

 the two, and consequently that the two are distinct species, 

 is sufllctently proved by two separate facts: 1st, that the 

 galls produced by the two arc invariably different, whence 

 it follows that the gall -generating poison, and consequently 

 the internal organs t]iat secrete that poison, must be different 

 in the two; 2nd, that the system of one form gives origin to 

 but a single type of Q, and the system of the other fonn 

 generates two entirely distinct and dimorphous pQ, and 

 consequently that the reproductive systems of the two must 

 be essentially different iu some part or parts of their internal 

 oi'ganization. 



For the satisfaction of those who are not acquainted with 

 the galls X3i*oduced by these two gall-Hies, I give drawings 

 ol each (Figs. 5 and 0) from the pencil of Mr. lliley. Figure 

 T) is the gidl produced by C. q. spongifica upon Black Oak, 

 and Figure (J is tlnit produced by C. q. inanis upon Red Oak. 

 Lest it should be imagined tliat it is the difference in the 

 species of oak that causes the dilVerence in the char;ioters of 

 each of these two galls, it is proper to refer tlie reader here 

 to the list that I formerly published (Proc. Enl . Soc. Phil. 

 IH, p. 63S, note)— and I could now add many more such 

 cases— where the same gall-fly produces the same gall upon 

 distinct species of oak. Moreover, liatzeburg, as quoted by 

 Osten Sacken, asserts from personal observation, "that the 

 European Cynips fecundalrix of the Quercus pedunculata pro- 

 duced the same gall as it produces upon the European oak 

 when it attacked some American oaks in his garden. ' ' {Ibid 

 I.P.24S0 



