File:Aquatic insects of California, with keys to North American genera and California species (1956) (19722797136).jpg

Title: Aquatic insects of California, with keys to North American genera and California species
Identifier: aquaticinse00usin (find matches)
Year: 1956 (1950s)
Authors: Usinger, Robert L. (Robert Leslie), 1912-1968
Subjects: Aquatic insects; Insects
Publisher: Berkeley, University of California Press
Contributing Library: University of Connecticut Libraries
Digitizing Sponsor: LYRASIS Members and Sloan Foundation

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351 Leech and Chandler: Coleoptera
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Fig. 13:46. Helodidae, larvae, a, Prionocyphon limbatus, showing tracheal reservoirs; b, Elodes minuta (European sp.), to show extruded anal papillae and abdominal air bubble; c-e, Scirtes tibialis, first, second, and later instar larvae (a, Good, 1924; 6, Treherne, 1952; c-e, Kraatz, 1918). experiments with larvae of the European Elodes minuta (1952) and of E. minuta and E. marginata (1954), concluded that the anal papillae do not play an important part in the respiration of the larvae (neither are they of consequence in the various dip- terous larvae which have them). Their chief function seems to be to absorb salts in the process of stabi- lizing the osmotic pressure of the haemolymph. The larva of E. minuta has large tracheal air sacs. By contraction of the abdominal sacs it extrudes a bubble from the last pair of abdominal spiracles. This bubble is held in place chiefly by apical semi-hydro- fuge hairs, and is in direct connection with the air in the tracheal system (fig. 13:466). Treherne found that larvae which had the terminal spiracles blocked to prevent formation of an air bubble, and the tip of the abdomen sealed to forestall protrusion of the papillae, could live less than half as long when submerged in well-aerated water as could untreated larvae. The same result was obtained when only the spiracles were plugged. Thus the terminal air bubble was the important respiratory mechanism. Normal larvae were found to consume about 4.50 cc. of oxygen per gram of dry tissue per hour, and the bubble functioned to extract oxygen from water even at relatively high concentrations. It also functioned to eliminate C02 at a greater rate than did the body surface; the papillae allowed it to escape much less rapidly, but still more than twice as fast as did the general body surface. Life history.—So little is known of the life his- tories of the Nearctic species of Helodidae that it is unsafe to generalize. The eggs are presumably laid in damp places near water; in the case of Priono- cyphon this may be in water-filled tree holes. The larvae are aquatic; those of only three North American species have been adequately described. Larvae of Scirtes tibialis Gue>in were said by Kraatz (1918:393) to eat the leaves of duckweed (Lemna minor); but Beerbower (1944:677) found those of S. orbiculatus (Fabricius) feeding on minute algae. Larvae of Prionocyphon limbatus are reported to eat the broken-down epidermal cells of various dead leaves in ponds. The larvae of Scirtes grandis Mot- schulsky of Ceylon were said by Nowrojee to be predaceous, but later authors doubt this. Those of S. championi Picado occur in water in the leaf axils of epiphytic bromeliads in Costa Rica. The specialized mouth parts of Elodes hausmanni Gredler (fig. lS'A7d,g), and of some other European helodids have been illustrated by Beier. The man- dibles with their brushes and the toothed parts of the hypopharynx work with machinelike regularity, gather- ing and filtering fine detritus from the surface of stones and underwater vegetation. The teeth on the anterior hypopharyngeal comb vary in shape and number, depending on the species and genus of the larva. Mature larvae of most genera leave the water and form pupal cells in damp soil. Those of Scirtes tibialis remain on the undersides of Lemna leaves; the pupa is attached by its anterior end and hangs freely (fig. 13:47c). Walsh found the pupae of Prionocyphon dis-

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