28 



PSYCHE. 



[February 189:. 



ON THE LIFE-HISTORY OF DIABROTICA 12-PUNCTATA OL1V. 



BY H. GARMAN, LEXINGTON, KY. 



This insect is deserving of especial 

 attention just now because it appears to 

 be undergoing a change of habit similar 

 to those undergone in the past by sev- 

 eral other native American insects, and 

 probably due to the destruction, by the 

 cultivation of land and by grazing, of 

 the wild plants upon which it has hith- 

 erto subsisted. This explanation of its 

 sudden appearance recently over a wide 

 extent of territory as a corn-infesting 

 insect seems to me the only one war- 

 ranted by the published facts of its his- 

 tory. 



Until iSSS Diabrotica 12-punctata 

 did not appear in the literature of eco- 

 nomic entomology as an important en- 

 emy of any of our staple crops. Mr. 

 B. D. Walsh, writing in 1S66 (Pract. 

 ent., v. 1, no) and referring to the 

 beetle, states that "it is very injurious to 

 flowers especially to Dahlias," and in- 

 fers that it is in part responsible for an 

 injury to the leaves of melons, cucum- 

 bers and other plants, of which one of 

 his correspondents complains. 



In 1S68 Walsh and Riley (Am. ent. 

 v. 1, 227) in reply to a correspondent in 

 Bushberg, Missouri, wrote of the same 

 beetle, "The yellow beetle with twelve 

 black spots which we herewith illustrate 

 (Fig. 168, twice natural size) and 

 which has been so destructive to your 

 water melons and Hubbard squashes, is 

 the 12-spotted Diabrotica." In the same 



place in reply to R. D. Parker of Man- 

 hattan, Kansas, these authors state that 

 insects sent to them for determination 

 are also D. 12-punctata. 



In 1S70 Prof. C. V. Riley (2d Mis- 

 souri Report, 66) wrote that the beetle 

 "may often be found embedded in the 

 rind of both melons, cucumbers and 

 squashes," a statement which is re- 

 peated in 1S72 by Mr. E. B. Reed (Ent. 

 soc. Ont., Report for 1S71, 91). 



Prof. S. A. Forbes somewhat extends 

 the knowledge of the food-habits of the 

 beetle by recording in his first report as 

 State Entomologist of Illinois (p. 104) 

 that it was observed Aug. 1, 1S82, feed- 

 ing on the pollen of corn and on the 

 blossoms of clover. 



One of the most notable cases of in- 

 jury by the beetle is that reported in 1SS8 

 by the editors of Insect life (v. 1, 58). 

 In an orchard at Hernden, Virginia, 

 planted chiefly in 1SS7, young apricot 

 and plum trees are stated to have been 

 badly injured in late April and early 

 May by the beetles, which devoured 

 the leaves as they unfolded. The land 

 on which the trees were planted was 

 mostly in corn in 1SS7, but a half acre 

 had been in melons. In concluding 

 their notice the authors use the follow- 

 ing words : 



"It is safe to say, however, that this occur- 

 rence is exceptional, and that it depended 

 almost entirely upon the peculiar circum- 



