description of the nervous system of the head appendages, and of the legs 

 and anal legs of Molanna angustata. Novak (1952) studied species of 

 21 genera and 4 families of the Annulipalpia (Rhyacophilidae, Philo- 

 potamidae, Polycentropodidae and Hydropsychidae) and six Integri- 

 palpia (Phryganeidae, Molannidae, Leptoceridae, Odontoceridae, 

 Limnophilidae and Sericostomatidae), and described the topographical 

 anatomy of the tracheal system of the larvae; Winkler (1959) studied the 

 musculature of the larva of Limnophilus flavicornis, and gave good 

 drawings of the muscles of head, thorax, legs, abdomen and some internal 

 31 organs; some of these drawings are reproduced here. Satija published a 

 number of papers (l959a-1959c; Satija, 1959, I960) on the structure of the 

 mouthparts and intestine of the larvae of caddis flies in connection with the 

 feeding habits of some species. 



In spite of the large number of publications and detailed studies of some 

 systems of organs, like those of Racie^ka, Novak and Winkler, the following 

 description of the anatomy of the internal organs of the larvae is not 

 complete. The data given refer to full-grown larvae. 



Musculature. The greater part of the head capsule is filled with the 

 muscles which activate the mandibles; the large adductor of the mandible 

 (musculus craniomandibularis internus) is the largest muscle of the head, 

 attached by a strong, partly sclerotized ligament to the inner process of the 

 triangle at the base of the mandible; this muscle is divided into two 

 branches (Figure 20) at about the level of the tentorium; it consists of an 

 upper and lower branch; the upper branch is divided into several bundles 

 which are attached to the dorsal wall of the posterior part of the head 

 capsule near the epicranial suture and the occipital foramen; the second 

 branch is attached near the ventral side of the occipital foramen. The 

 traces of the attachment of the muscles are visible on the head as rows 

 and groups of large dots, the situation of which is constant in spite of the 

 considerable variation in size, coloration, their relative position to each 

 other, and other secondary characters. The labrum (Figure 21 ) is moved 

 by one muscle (musculus frontolabralis) and two paired muscles on the 

 sides, which originate on the frons. Relatively large muscles, moving the 

 maxillolabium (m. tentoriocardinalis and m. tentoriostipitalis) are attached 

 to the tentorium (Figure 22); smaller muscles connected with the mentum 

 and other parts of the maxillolabium are shown in Figure 22. 



The anterior part of the intestine inside the head is connected with the 

 dorsal and ventral wall of the head by thin muscles at some points. 



The thoracic segments and abdominal segments 1 — 9 and their 

 musculature are illustrated in Figures 22 and 23—2 6. The strong muscle 

 extending from the posterior margin of the prothorax to the dorsal margin of 

 the occipital foramen retracts the head beneath the pronotum; several 

 muscles, including the relatively large dorsal muscle of the pronotum 

 (m. pronoto-postoccipitalis medialis) and the lateral muscle attached to the 

 ventral margin of the occipital foramen move the head laterally and bend it 

 downward. The strong basocoxal muscle extends from the posterolateral 

 part of the pronotum to the coxa of the foreleg, moving the forelegs. 

 Dorsally, along the thoracic segments from one segment to another and along 

 the abdomen runs a broad dorsal longitudinal muscle; a similar longitudinal 

 muscle is present on the ventral side; the above muscles effect longitudinal 



27 



