1907.1 White-grubs and May- beetles. • 449 



grubs, there are three other very abundant kinds which resemble 

 closely the injurious species, although they are themselves harmless 

 in the grub stage. 



Eight of the species known to be injurious belong to the genus 

 Lachnosterna and one to the genus Cyclocephala. Of the abundant 

 but harmless grubs, one, frequently called the muck-worm because it 

 lives in stable manure, is known to science as Ligyrus relictus ; an- 

 other, called the carrot-beetle in the adult stage, is L. gibbosa ; and 

 the third is the larva of the green June-bug of southern Illinois and 

 of the Southern States generally, known in the beetle stage as Allo- 

 rhina nitida. All the last three species are injurious as beetles, but 

 only one of them, the larva of the carrot-beetle, is at all injurious as 

 a grub, and then only slightly or occasionally so. The eight species 

 of Lachnosterna known to be injurious in Illinois are L. fusca, 

 rugo'sa, inversa, implicita, gibbosa, tristis, ilicis, and hirticula ; and 

 the injurious Cyclocephala is C. immaculata. 



Life Histories of the' Injurious Species. — The life histories of 

 the white-grubs of the genus Lachnosterna are very imperfectly 

 known, especially as to the length of time required for the growth 

 and development of a complete generation. The literature of the 

 subject records, in fact, but a single case in which a Lachnosterna 

 has been reared from the Q^g to the adult. An tg^ of L. arcuata 

 laid in Washington about June 8, 1893, hatched in approximately 

 eleven days, and changed to the pupa August 8, 1895, and to the 

 beetle twenty-three days later.* As this beetle would doubtless have 

 hibernated in the earth to emerge the following spriiig and lay its 

 eggs in June, the entire period from the e^g to the egg again was 

 three years. This is the length of the life cycle which has com- 

 monly been inferred, from circumstantial evidence, for our species 

 of Lachnosterna generally. It is worthy of note, however, that Melo- 

 lontha vulgaris, the European white-grub nearest in classification 

 and habits to our American species, has been found, according to 

 Xavier Raspail, to have, in France, a period of three or four years 

 — the shorter period if the years are moist and the longer one if 

 they are dry.f In Germany, on the other hand, this species has a 

 four-year period at the north and a three-year period at the south, 

 with various occasional exceptions and irregularities of appearance; 

 and a related species, M. hippocastani, has a five-year period in north 

 Germany. Our American species of Lachnosterna will probably be 

 found to present similar variations of life history. 



*"Biolog-ir Notes on Ihe May-beetle Lnchnosterna arcuata Sm." By F. H. Chittenden. 

 Bull. 19, N. S., Div. Ent., U. S. Dept. Aer., p. 77. 



fBulI.de la Soc.Zool. de France, 1891, p. 271; M6m.de la Soc. Zool. de France, 1893, T. TI., 

 p. 202. 



