137 
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 
Lachnostcrna 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. fiisca, 
rugosa, inversa, implicita, gibbosa, tristis, ilicis, and hirficula; and 
the injurious Cyclocephala is C. immacidata. 
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 fr6m the egg to the adult. An egg 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 spring and lay its 
eggs in June, the entire period from the egg 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, 
w^th 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-ic Notes on the Mav-beetle Lachnosterna arcuata Sm." By F. H. Chittenden. 
Bull. 10, N. S., Div. Ent., U. S. Dept. Agr., p. 77. 
tBull. de la Soc. Zool. de Prance, 1891, p. 271; Mem. de la Soc. Zool. de France, 1803, T. VI., 
p. 202. 
