THE MAIZE BILLBUG. 



21 



Elytra little wider than tlie thorax ; striae usually deep and well defined, 

 distinctly closely punctate ;. intervals with first, third and fifth elevated, with 

 two or more series of rows of fine punctulation ; first or sutural with basal 

 third triseriately, posterior two-thirds biseriately punctulate ; third widest and 

 most elevated, with four or five rows of fine punctulations ; fifth biseriately 

 punctulate; seventh little or not at all more elevated than the remaining inter- 

 vals; intervals 2, 4, 6, 8, as also 7, more coarsely and closely uniseriately punctu- 

 late. Pygidium deeply, coarsely and rather sparsely punctate, with sparse 

 golden yellow hairs proceeding from the punctures and forming a short tuft 

 each side, frequently abraded. 



Lower surface coarsely and rather densely punctate, scarcely less strongly 

 at the middle than at the sides, punctures largest at the middle of the meta- 

 thorax. Punctures of the metepisterna (side pieces) more or less confluent. 

 Second, third and fourth abdominal segments 

 nearly uniformly punctured throughout, like 

 the legs. 



S . — First abdominal segment very con- 

 cave ; pygidium truncate at apex. 



$. — First ventral scarcely different; pygid- 

 ium narrowed and rounded at apex. 



Aside from the differently shaped pygidium 

 and the slightly shorter and less compressed 

 rostrum there is little difference between the 

 sexes. 



Length, 10-15 mm., width, 4.5-6.0 mm. 



The adults begin to issue about the 

 middle of August and continue to do so 

 until the middle of September. Some 

 of them leave the pupal cell, but most 

 of them remain there for hibernation. 

 The adults that leave the pupal cell in 

 the late summer disappear; continued 

 search in every situation until Decem- 

 ber failed to reveal a single individual. 

 It is evident that they left the cornfield in which they developed, 

 and it is very probable that they found their way to some dense, 

 coarse grass (T. dactyloides) , which is abundant in the locality, 

 The adults hibernating in the pupal cells issue from them in late 

 spring, about the time young corn is sprouting. The beetles are 

 rarely observed on account of their quiet habits and because they 

 are covered with mud — a condition which is more or less common 

 among several species of this genus and is caused by a waxy exuda- 

 tion of the elytra, to which the soil adheres. The presence of the 

 adults of this species in a cornfield is made evident by the withering 

 of the top leaves of very young corn plants, the plants having been 

 severely gouged. The adults kill the small plants outright and in- 

 jure the larger ones beyond repair. After the plants grow 10 to 15 

 inches tall they do not kill them, but gouge out such large cavities 

 in the stalks that they become twisted into all sorts of shapes (PL I, 



Fig. 10. — The maize billbug 

 Four times natural size, 

 nal.) 



Adult. 

 (Origi- 



