VI. Trichoptera.

Publisher Website
Google Scholar
Abstract
Six specimens of caddis-flies as well as caddis cases* are present in the collection of Latah fossils. Considering their aquatic development, it is not surprising that these insects should be represented, but the number of species is much larger than one would expect in a collection of this size. Fifteen per cent of all the specimens belong here. The magnitude of this proportion takes on some significance when we compare the trichopterous fauna of the Latah beds with that of the Florissant Shales, Scudder's examination of about twenty thousand Florissant insects showed that less than 4% of the species were Trichoptera, which means that the caddis-flies seem to he about four times as numerous at the Latah beds as at those of Florissant. It is also interesting to note that of the six Latah specimens, five are Limnephilids (representing five species) and the other is a Phryganea. In marked contrast to this, the specimens in the Florissant Shales comprise 95% Hydropsychids, 4% Phryganeids, and 1% Limnephilids. In other words, the family Hydropsychidæ, which is far and away the most abundant at Florissant, is absent in the Latah collection, while the family Limnephilidæ, of which only two species have been found in some twenty thousand Florissant insects, is represented by five species out of a total of 41 fossils from the Washington deposit. It must be admitted, of course, that these statements lose some of their force in view of the small number of Latah insects known, but I nevertheless believe that they have considerable significance. The Hydropsychidæ, which are so abundant at Florissant, breed only in rapid streams or active waters of lakes. The Phryganeidæ and very nearly all the Limnephilidæ, on the other hand, develop in standing water which usually contains much plant life, or in quiet streams. This would seem to verify Knowlton's conclusion, quoted above, that the lake which deposited the beds was shallow and contained a diverse flora.
Keywords

This publication has 0 references indexed in Scilit: