NATURAL SCIENCES OP PHILADELPHIA. 213 



4tk Section. 



Ungues with, several notches on the underside, (and not with long teeth aB 

 in the other sections of the genus.) Forceps of the <$ belonging to the same 

 typical form with that ofDicranomyia, but with more elongated, slender 

 lobes. (Fig. 1 and 2.) 



L. defuncta. Fusco-cinerea, thorax vittis tribus nigro-fuscis, interme- 

 dia capillari ; pedes nigro-fusci, femora versus apicem annulo albido ; alae 

 fusco maculatse ; long. lin. 3^4. 



Head cinereous ; front and vertex almost black in the middle ; proboscis, 

 palpi and antennae fuscous ; joints of the fiagellum subglobular, with short 

 verticils. Thorax cinereous with a yellowish reflection ; three dark brown 

 stripes on the praescutum, the intermediate one capillary ; the lateral ones ab- 

 breviated before, and extended over the scutum behind ; pleurae variegated 

 with brown ; halteres pale with black knobs ; coxae cinereous, feet brown, 

 base of the femora tawny ; a very distinct whitish ring at a distance equal to 

 its own width from the tip of the femora ; ungues with several small notches 

 on the underside. Abdomen blackish cinereous ; posterior margins of the 

 Segments paler ; genitals pale. Wings subcinereous, spotted with blackish 

 brown ; subcostal area infuscated at four intervals ; several spots, forming a 

 short band, along the central cross-veins ; series of small, round dots along the 

 middle of the areas ; a larger spot in the axillary area, at the tip of the axillary 

 vein ; stigma square. 



Common near Washington, especially in May. It occurs near running 

 water, and is often found on stones or rocks over which a thin sheet of water 

 is running. I possess the same species from the Trenton Falls and Quebec, 

 (nob.) and from Maine (Mr. Packard.) 



Compared 8 males and 4 female specimens. 



5th Section. 



(Limnobiae v e r ae.) 



Collare long, well developed ; joints of the antennae (except the basal ones) 

 elongated, subcylindrical, slightly incrassated at the base ; verticils long, in- 

 serted on the incrassation and before the middle of the joint;' ultimate joint 

 sometimes twice as long as the penultimate, and apparently consisting of two 

 joints ; feei stout ; ungues strong with a large tooth in the middle of tbe un- 

 der side and smaller ones nearer to the base ; wings long and broad ; the tf 

 forceps consists of two subcylindrical, coriaceous halves ; to each is attached 

 a pair of closely contiguous, curved moveable lamellae ; the outer lamella seems 

 to be horny ; the inner one is of a softer consistence ; they vary in size and 

 form in different species. (See the figures 6 and 7 of the plate.) The differ- 

 ence between their structure and that of the forceps ofDicranomyia seems 

 to be more apparent than real, and to depend entirely on the great distension 

 of the soft portion of the forceps in the latter genus ; the solid, horny parts 

 seem to have the same structure in both genera. Thus, inL. solitaria the 

 soft parts, marked ^*on the plate, might be the analogues of the large lobes of 

 Dicranomyia, only in a rudimentary state. 



The colors of this group are bright (generally ferruginous or yellow) with 

 well marked brown stripes and spots. The habits are terrestrial ; the larvae 

 live in decaying wood or fungi ; the perfect insect is found in localities where 

 these matters abound. (The larva of L. annulus, a European species of 

 this group, is described by Van Roser, as being, in shape and color, like a 

 common earthworm ; it lives in decaying wood ; that of L. xanthoptera, 

 another European species, has been found by Stannius and Bremi in 

 Agaricus.) 



The contrast between this section and the 3d (Dicranomyia) is great, 



1859.] 



