398 



shown in Figure 17, Plate XXIV; labial papillse as in Figure 4, Plate 

 XXV. 



Localities, Meredosia, Naples, La Grange Lock, and Grafton — all 

 on the Illinois River. 



Tanypus sp. B 



Length, 5 mm. Labial plate as in Figure 5, Plate XXV; body 

 slightly flattened ; head parts pale in color ; antenna and maxillary 

 palpus as in Figures 8 and 9, Plate XXIV; posterior pseudopods not 

 much elongated ; anal respiratory organs large, not acute at apices, the 

 dorsal pair of hairs present; dorsal tuft with about twelve hairs, the 

 papillae about five times as long as thick. 



Localities, Averyville, Pekin, Havana, Thompson's Lake, Ma- 

 tanzas Lake, Meredosia, and La Grange Lock — all on or connected 

 with the Illinois River. 



CHIRONOMIN^ 



The species included in the Chironomincu form a more complex 

 group than do those contained in the other two subfamilies, but, 

 nevertheless, one which nowhere lends itself to a satisfactory subdi- 

 vision which will apply to all stages, and lacking this I do not consider 

 it expedient to subdivide them except in the imago stage. Many quite 

 striking larval characters are found in species the imagines of which 

 are so similar to others which do not possess these larval characters 

 that they are separable with difficulty, while, on the other hand very 

 dissimilar imagines have often very similar larvae. The presence of 

 the medio-cubital cross-vein of the wing in Diauicsa at once dis- 

 tinguishes the imago from any other chironomine species and seems 

 to link it closely with Tanypincc, but the antennal difference between 

 the sexes and the type of larva unmistakably point to its closer affinity 

 with the present group. The case-forming habit of the genus Tany- 

 tarsus is an elaboration of the burrowing habit of other chironomid 

 species, which, taken in conjunction with the hairy wings of the 

 imagines indicates a good generic distinction from their closest rela- 

 tives. Many of the generic divisions are perfectly sound, but within 

 the last few years some arbitrary divisions have been proposed, nota- 

 bly by Kieffer, which may be very useful to systematists who can ap- 

 preciate the minutiae of the distinctions, but which are, I am confident, 

 not in keeping with the natural grouping of the species. This convic- 

 tion must impress itself upon any one who studies the larval and pupal 

 stages, which, in nearly all orders, furnish a better basis for classifica- 

 tion than do the imagines. In the present paper the object which has 



