ENTOMOLOGICAL INTELLIGENCE. 
47 
Roeselii and C. Isevigatus, the variety of the female of the former 
being known under the name of Dyticus dispar, Rossi, In Acilius, 
as restricted by Eschscholtz, A. semisulcatus and A. abbreviatus 
are female varieties of the same species. In Thermonectus the 
females also vary in the smooth or punctate base of the elytra. 
The same remark also applies to various species of Hydaticus; and 
Dr. Erichson also considers that there are also dissimilar females in 
certain species of Hydroporus. 
The Hydaticus verrucifer. Sahib., however, is even more interest¬ 
ing in this respect than any of the before-mentioned species, and has 
formed the chief subject of Count Mannerheim's memoir. This species 
was formed by Aube into a separate section of the genus, with the 
character of simple tarsi in both sexes, whilst Dr. Erichson regards 
it as the abnormal female of Hydaticus zonatus. Having received a 
number of living specimens of this supposed species, Count M. ob¬ 
served that some of those with smooth elytra possessed dilated tarsi, 
and others simple tarsi. The former, as well as some of the latter, 
of these individuals w^ould therefore belong to H. zonatus, and the 
remainder of the latter would be males of the verrucifer. But, in 
respect to the punctuation and structure of the thorax and elytra, 
Mannerheim observed a complete gradation from the rugose 
verrucifer to the smooth zonatus ; whilst a dissection of numerous 
individuals proved that every specimen with dilated anterior tarsi 
were males, and that every specimen with simple tarsi were females; 
and amongst these latter were found the specimens with simple 
tarsi and radiated impressions on the thorax, which M. Aube 
regarded as the males of verrucifer. Count Mannerheim, in con¬ 
clusion, endeavours to trace the analogy which in this respect exists 
between these w^ater-beetles and other species of insects in wdiich we 
find a marked diversity of structure ; instancing, first, the neuters 
of social Hymenoptera; and, secondly, the variations in the size of 
the horns of the head and thorax and dilatation of the hind legs in 
certain beetles. But in neither of these tribes does the analogy 
hold good, because, first, the neuter Hymenoptera are but imperfect 
females, whereas, the smooth-backed female Dytici have been 
repeatedly captured in copida with the dilated-footed males; and, 
secondly, because, it is the males only amongst the beetles which 
offer such variations which, moreover, are gradual, whereas, no 
intermediate gradation has been observed between the smooth and 
sulcated female Dytici. 
