148 THE CAUSES WHICH PROPAGATE 



and is divided in some species by a central canal^ which receives 

 the sutural tips of the elytra into two somewhat triangular limse, 

 with the apex posterior. In many the clasp that works the lima, 

 or limse, is seen in an elong-ate callosity close to the sutui-al ex- 

 tremity of the elytra. The stridulation of the genus Clythra, 

 Laich., was discovered by Mr. G. R. Crotch. Our Clythra 

 quadri-punctata, L., an oblong beetle with orange, black-spotted 

 elytra, is found disporting on tree-trunks near the nest of 

 certain wood-ants, among whom it passes its youthful stages, 

 creeping about in a portable case, like certain micro-Lepidop- 

 tera. In specimens of this insect kindly sent me by Dr. G. C. 

 Champion, I found a lima in a glossy patch, somewhat trian- 

 gular, and minutely striate, lying at the anterior edge of the hairy 

 last dorsal arc of the abdomen, which was evidently sounded 

 on the indurated, faintly-produced tip of either wing-case. The 

 genus EpilacJma also, I believe, stridulates,and in the same fashion. 

 Besides the South European genius Pimelia, and perhaps the 

 Black Beetles {Blaps), which, Westring states, produce a sound 

 by the friction of the abdomen against the wing-covers, there is 

 the following mention of the creaking of Heteromera in " The De- 

 scent of Man,'-* in which we are presented with an exception to the 

 rule that both sexes sing. Dr. Darwin there says : — "Mr. Crotch 

 has discovered that the males alone of two species of Hellopaflies 

 possess stridulating organs " ; and that " he examined five males 

 of //. gihhus, a small black lenticular coleoj^teron found on sand, 

 and that in all these there was a well-developed rasp, partially 

 divided into two, on the dorsal surface of the terminal abdominal 

 segment; whilst in the same number of females there was not 

 even a rudiment of the rasp, the membrane of this segment 

 being transparent and much thinner than in the male. In the 

 exotic (j^. cribratostriatus) , the male has a similar rasp, except- 

 ing that it is not partially divided into two portions, and the 

 female is completely destitute of the organ.'" This hetero- 

 geneous group of beetles has been founded on the circumstance 

 that the feet or tarsi of their hind legs have often a joint less — 

 or rather, one marked and undeveloped — and it is this circum- 

 stance which confers a pace slow and solemn on our darkling 

 churchyard kind and on that of his southern relatives that stalk 

 among the tombs of Italy and of Egypt. 



