262 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 9 



The studies on the habits and Hfe-histories have been conducted 

 both in the field and in the laboratory. For instance, most of the 

 studies to determine the habits of beetles, their food habits, etc., and 

 the habits, etc., of the grubs have been made in the field with extensive 

 observations and feeding experiments in confinement to corroborate 

 our field observations. On the other hand, detailed studies of the 

 various stages of the life cycle, the total life cycle, and the like, were 

 conducted largely in breeding cages approximating as nearly as possi- 

 ble natural conditions. A discussion of the different cages used has 

 already been given in this journal.^ 



Life-history Investigations 



In this paper we will undertake to show only the more general con- 

 clusions and those which have a definite bearing on the economic phase 

 of the subject. To date eighteen species of Lachnosterna have been 

 reared from egg to adult and there are at least half as many more, 

 the life cycles of which we are reasonably certain although it will be 

 another year before we will have actually bred adults from eggs. The 

 accompanying table will give data relative to the grosser points in the 

 life cycle of the species studied at Lafayette. It will be seen from this 

 that one species — Lachnosterna tristis — ^invariably has a two-year 

 cycle in the latitude of Lafayette while eleven species, namely L. 

 arcuata, fusca, vehemens, rugosa, ilicis, grandis, fraterna, hirticula, 

 inversa, bipartita and congrua, invariably have a three-year cycle 

 according to our experiments. Two species, L. crenulata and L. eras- 

 sissima, have a three-year life cycle as a rule but our experiments show 

 that it may be extended in the latitude of Lafayette to four years, and 

 several other species, L. gibbosa, burmeisteri and implicita, usually 

 have a three-year cycle but in some cases it may be cut to two years. 

 However, all of the Lachnosterna of economic importance in this lati- 

 tude have a three-year cycle. 



Latitude naturally has a great influence on the length of the life 

 cycle of the same species. For instance, L. grandis has a life cycle of 

 three years in the latitude of Lafayette but at Trout Lake in the 

 northern end of Wisconsin, it undoubtedly has a four-year life cycle. 

 We now have cages at this point started in 1914 and 1915 and the 

 small size of the grubs this summer in cages started in 1914 is evidence 

 enough to show that the grubs cannot mature in less than four years. 

 Further in 1911 the beetles (mostly L. grandis with a few L. dubia) 

 were very abundant and in 1912 and 1913 the grubs were unusually 

 injurious to seedling conifers. In 1915 the beetles were again very 

 abundant. Furthermore, the combined seasonal temperatures for 



1 Jour. Econ. Ent., Vol. 8, No. 1, 1915, p. 135-139, 3 pis. 



