Feeding. Caddis fly larvae are a highly differentiated group of bottom- 

 dwelling organisms; they feed on a wide variety of organic matter on the 

 5 6 bottom. Plant detritus at various stages of decomposition, aquatic plants 

 (and also animals) are their food. Some larvae are narrowly specialized 

 in feeding, but other larvae feed on various foods and under certain 

 conditions may change from their preferred food to a less favorable one. 



A large group of larvae feed on detritus of decomposing organic matter 

 with its rich bacterial and fungal flora; numerous species feed readily 

 on fallen leaves when the leaves are already black; thus, the caddis fly 

 larvae form a trophic connection with terrestrial vegetation; species feeding on 

 dead plankton on the bottom also feed on pelagic organisms. Phytophagous 

 species feed on algae and plants of the phytobenthos covering stones. The 

 predators hunt small animals by building nets in which plankton animals 

 are also caught. Species living on mixed food feed both on plant detritus 

 and plants and on minute animals. 



Depending on the available food, the feeding of the larva also changes, 

 which explains the frequent differences in observations on the feeding of the 

 same species in different water bodies in different seasons (these 

 observations often refer to larvae of different age). 



A number of studies have been made on the feeding of the larvae 

 (Siltala, 1907; Gatjen, 1926; Popova, 1927; Slack, 1936; Kolenkina, 1951; 

 Kashkin, 1958; Kachalova, 1960:149-151; Smirnov, 1962). Feeding has 

 repeatedly been described in surveys and papers on the morphology or 

 biology of species of caddis flies. * 



In the suborder Annulipalpia, mixed feeding exists in the microphagous 

 larvae of Psychomyiidae and Philopotamidae which live in curved vermi- 

 form galleries (Psychomyiidae) or in long tubes which are wider at the end 

 (Philopotamidae) built on the bottom, on stones or other objects; these 

 larvae collect particles of slime, fine detritus and minute animals together 

 with fungi and bacteria which develop in brownish slimy deposits on the 

 tubes; larvae of Philopotamidae collect this mixed food with the membranous 

 labrum with its comb of thin, curved, hairlike spinules at the anterior 

 margin (Figure 84), and with tufts of long hairs on the maxillae. In the 

 suborder Annulipalpia, phytophagous feeding is characteristic for the case- 

 bearing larvae of Glossosomatidae, which feed on plants clinging to stones; 

 57 among these plates diatoms which are eaten together with other algae, 

 bacteria and other microfauna predominate. The larvae scrape off the 

 plants with their long spatulate mandibles (Figure 85); after having eaten 

 the plants at one end of the case, the larva turns round in its case and eats 

 the plants at the other end of the case, and then moves to a new feeding 

 surface, Hydroptilidae (Figure 86) are highly specialized phytophages of 

 Annulipalpia, especially species of Agraylea, Oxyethira and others, 

 as they feed on filamentous algae; they move along a thread, bite through 

 one cell after another and suck out the content; the intestine of the larva 

 becomes green; the larvae of Orthotrichia tetensii feed on large 

 unicellular algae (Figure 87). 



* The old literature on the feeding of caddis fly larvae (including Reaumur, 1737:155; Pictet, 1834:113-114; 

 Kolenati, 1848:51; Klapalek, 1888:12; McLachlan, 1863:8532-8533; Fr. and Miiller, 1879:387; Goody, 

 1880:146; Ulmer, 1900:850) and other sources on this problem has been listed by Siltata (1907:29-34). The 

 feeding of Hydroptilidae has been described by Nielsen (1948:163-166). Satija (1959a, 1959c) deals with the 

 feeding of some species and also gives descriptions of these species and of the characteristics of their 

 intestine. 



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