A STUDY OF THE GENUS MONOXIA — BLAKE 147 



the claws of the sexes in the majority of the species, and its inclusion 

 in this subfamily is purely artificial. 



Although Monoxia is an easily recognized, homogeneous group of 

 species occm-ring chiefly in western North America and having, so 

 far as is known, the distinctive larval habit, peculiar among closely 

 related genera, of mining leaves, it is exceedingly difficult to find 

 characters that in all cases will separate it from Galerucella. Gener- 

 ally the claws of the male are toothed and those of the female simple, 

 but not always. Generally the antennae of Monoxia are shorter, but 

 even here it is extremely difficult at times to draw a line. Usually, 

 the prothorax is longer and more deeply impressed and the elytra, 

 narrower and with a less broadly rounded apex and a narrower lateral 

 margin, and the abdomen of the male has a "deflexed pygidium," but 

 certain species of Galerucella are as narrowly oblong as Monoxia, and 

 at least four species of Monoxia do not have a very evident pygidium 



in the male. 



DESCRIPTION OF THE GENUS 



The body is elongate-oblong-oval, more or less densely pubescent 

 with short, fine, and usually recumbent hairs. The head is with- 

 drawn into the prothorax to behind the eyes; it is moderately wide, 

 very little produced in the lower front, and with a median impressed 

 line; there is little evidence of frontal tubercles, and the upper part 

 of the head is punctate and pubescent. The antennae are short, not 

 half the length of the body, and do not come much below the elytral 

 humeri. The first and third joints are longest, the fourth and remain- 

 der, except the apical one, about the same length, gradually thicken- 

 ing. In the male, the joints are slightly longer and slenderer, while 

 in the female the eighth, ninth, and tenth joints frequently are thicker. 

 The prothorax is usually scarcely twice as broad as long, often con- 

 siderably less, and only in one group of species over twice as broad as 

 long; the sides are arcuate or angulate, sometimes nearly straight, 

 but usually broadest in the middle, with a little tooth at the basal 

 angle, more or less prominent in different species. The basal margin 

 is usually sinuate over the scutellum and joins at an obtuse angle with 

 the sides. The upper surface is uneven and has a median channel and 

 lateral depressions. In some species these depressions are very pro- 

 nounced, in others a mere unevenness of surface. The surface is 

 generally densely punctate and pubescent. The scutellum is trun- 

 cate. The elytra are broader than the prothorax, with parallel sides 

 and a narrow margm which extends nearly to the tip ; the humeri are 

 prominent, and there is often a long incurving intrahumeral depres- 

 sion extending to behind the middle. In some species there is also 

 a linear lateral depression behind the middle. The surface is more 

 densely and finely punctate than in most species of Galerucella and 



