THE CANADIAN ENTOMOLOGIST. 93 



developed that the formation of galls could be observed, and again the galls 

 were those of Spath. albipes. Out of the 144 buds marked, galls were 

 found on 68, with about 300 galls. The oak chosen was a small shrub 

 four to five feet high, easy to be examined, and showed no where any- 

 other galls. 



Out of the collected galls a large number of Spath. albipes was raised 

 in the first half of June, and were put in a breeding cabinet with a small 

 oak tree. As no copulation nor oviposition was observed, Dr. Adler 

 decided to try observation in the open air. He succeeded June 3rd in 

 finding several females of Spath. albipes in the act of oviposition, and 

 secured six wasps, several leaves, and marked four leaves on which he had 

 observed oviposition with a thread. The lens showed that an egg was 

 deposited. The secured wasps were put on the small oak in the breeding 

 cabinet, and now the wasps were observed ovipositing on two leaves. The 

 next day the wasps were examined, and showed the receptaculum seminis 

 full of spermatozoa. On June 5th and 6th several more wasps in the act 

 of oviposition were observed, and six leaves marked. In the first fort- 

 night no change in the leaves was seen ; in the third week the substance 

 of the leaf where the egg was deposited was visibly thickened, the larva had 

 left the egg, and the formation of the gall began. Then the progress was 

 very slow ; after four to five weeks, in the beginning of July only a very 

 small hairy disk was seen, and only in the end of July the galls could be 

 recognized with certainty as those of Nenroterus fumipennis.. On all ten 

 leaves such galls were produced. 



I have given here the substance of Dr. Adler's experiments only for 

 one pair of individuals, but in the same manner the memoir contains them 

 for seven pairs ; two of these, Ncuroterus laeviusculus and Spatheg. tricolor, 

 Aphilotrix Sieboldii and Andriats testaceipes, are not mentioned by Mr. 

 P. Cameron. 



I think every student will be puzzled to find such detailed obser- 

 vations unmentioned in Mr. Cameron's paper, when he asks 

 if a consideration of the biology of the species named affords any 

 reasonable evidence in favor of this rather startling hypothesis (p. 154). 

 The only evidence Mr. Cameron tries to give against it is that, if the species 

 are correlated in the way indicated, we ought to find the two forms equally 

 abundant, and in close proximity to each other. He states that only 

 one of the five pairs quoted by him are found together, the other four 

 are not. This fact, if true, would be certainly of importance; nevertheless, I 



