THE STATE ENTOMOLOGIST. 51 



and expensive work to its consideration, decided that it is single- 

 brooded, and that it hybernates in the beetle form above ground. 

 Since the writings of Harris and Fitch, and since the publication of 

 Dr. Trimble's work there have been other papers published on the 

 subject. The first of these was a tolerably exhaustive article, by Mr. 

 Walsh, which appeared in the Practical Entomologist (Vol. II, No. 7), 

 in which betakes the grounds that the Curculio is single-brooded; 

 though subsequently he came to the very different conclusion that it 

 was double-brooded, (First Annual Rep., p. 67). In the summer of 

 1867 I spent between two and three weeks in Southern Illinois, during 

 the height of the Curculio season, and closely watched its manceuver- 

 ings. From the fact that there was a short period about the middle 

 of July, when scarcely any could be caught from the trees, and" that 

 after a warm shower they were quite numerous, having evidently just 

 come out of the ground,* I concluded that it was double-brooded and 

 communicated to the Prairie Farmer of July 27th, 1>67, the passage to 

 that effect, under the signature of "V," which is quoted by Mr. Walsh 

 (Rep., p. 67), as corroborative of its two-brooded character. Subsequent 

 calculation induced me to change my mind, and I afterwards gave it as 

 my opinion that there was but one main brood during the year, and 

 that where a second generation was produced it was the exception, 

 (Trans. Ills. State Hort, Soc, 1867, p. 113). Finally Dr. E. S. Hull, of 

 Alton, Illinois, who has had vast personal experience with this insect 

 read a most valuable essay on the subject, before the meeting of the 

 Alton (Ills.), Horticultural Society of March, 1868, in which he evi- 

 dently concludes they are single-brooded, and that they pass the win- 

 ter, for the most part, in the preparatory states, underground. 



Now, why is it that persons who, it must be admitted, were all 

 capable of correct observation, have differed so much on these most 

 interesting points in the economy of our Plum Curculio ? Is there any 

 explanation of these contradictory statements? I think there is, and 

 that the great difficulty in the study of this as well as of many other 

 insects, lies in the fact that we are all too apt to generalize. We are 

 too apt to draw distinct lines, and to create rules which never existed 

 in nature — to suppose that if a few insects which we chance to watch 

 are not single-brooded, therefore the species must of necessity be 

 double-brooded. We forget that Curculios are not all hatched in one 

 day, and from analogy, are very apt to underrate the duration of the 

 life of the Curculio in the perfect beetle state. Besides, what was the 

 exception one year may become the rule the year following. In 

 breeding butterflies and moths, individuals hatched from one and the 

 same batch of eggs on the same day, will frequently, some of them, 

 perfect themselves and issue in the tall, while others will pass the 

 winter in the imperfect state, and not issue till spring; and in the case 



*I hare of tpn noticed, and the fact has been remarked by others, that insects which have been 

 comparatively inactive for many days, in dry weather, fly freely after a warm showf r, and it is 

 possible that the increase of the Curculio after such rains is partly due to their flying in more vigor- 

 ously from the surrounding woods. 



