THE ARCUATE MAY BEETLE. 



75 



THE ARCUATE MAY BEETLE. 



{Laehnosterna arcuata Sm.) 



Since the publication of Dr. Forbes's reports on these insects the 

 larvae of our common L. arcuata have frequently been sent to this 

 office, and we have been able to identify the species, at least approxi- 

 mately, which, of course, was impossible before that time. 



To obtain fresh specimens of the early stages 

 of this species for illustration and study, a n um- 

 ber of beetles were captured at the electric 

 lights of Washington City, placed in a jar of 

 earth May 25, 1898, and kept supplied with oak 

 leaves for food. Eggs were not deposited at 

 once, and in fact not until about the beginning 

 of the second week in June, the exact date not 

 having been ascertained. The parent beetles 

 died the following week. The first larvse hatched 

 on the night of June 23, and eggs were still 

 hatching on the mornings of the 24th and 25th. 



Fig. 17. — Laehnosterna arcuata: 

 a, male clasper, from front or 

 above; b, right clasper, from 

 side ; c. left clasper ; d, ventral 

 characters of male; e, genital 

 structure of female— all en- 

 larged (adapted from Smith in 

 Insect Life, vol. i.) 



DESCRIPTIVE. 



The following brief descriptions will assist 

 with the illustrations iu the recognition of the 

 species in its different stages. It should be remarked, however, that, 

 with the possible exception of that portion of figure 16 lettered/, this 

 illustration will apply almost equally well to all or nearly all of the 

 seven species of Laehnosterna, formerly grouped in collections as/wsc«, 



and now included in what is termed, for con- 

 venience, the fusca group. The specific differ- 

 ences between arcuata and fusca are brought 

 out in the illustrations of their sexual charac- 

 ters (figs. 17 and 18). 



The egg. — The eggs of Laehnosterna are oval 

 when first deposited, but in their growth swell 

 by absorption, as has been pointed out by 

 Dr. Forbes, to a larger size, becoming just be- 

 fore hatching more broadly oval or nearly 

 spherical. The eggs are subject to consider- 

 able variation in form and outline. Eggs of 

 L. arcuata, just about to hatch, vary in width 

 from 2 to 2J mm , and in length from 2 J to 3 mm . 

 When newly laid they are nearly white and 

 rather moderately polished, but with their growth they become darker 

 and subopaque. The surface is apparently smooth and without sculp- 

 ture. In consistency the eggs are quite firm, strong, and elastic. An 

 egg is shown in outline, about three times the natural size, at c, fig. 16. 

 Comparison of the eggs of Laehnosterna of different species with 

 those of Euphoria and Ligyrus shows a very close agreement in shape, 

 color, and general appearance. 



Fig. 18.— Laehnosterna fusca: a, 

 male claspers, from front; b, 

 right clasper ; c, left clasper ; d. 

 ventral characters of male; e, 

 genital structure of female— all 

 enlarged (adapted from Smith in 

 Insect Life) . 



