Dobsonflies

Megaloptera. Spanish: Perros del agua (larvae, Mexico).

This is a small order, related to the Neuroptera (Penny 1977, 1983). There are two families, the large Corydalidae (BL 8— 12 cm, wingspan to 16 cm) and the much smaller Sialidae (BL to 25 mm). The Corydalidae ("dobsonflies") are widespread and dominant in mainland Latin America (only a single Antillean species on Dominica), with 7 genera and 47 species. Protochau-liodes and Archichaulides are found in southern Chile and have their congeners in Australia. The North American Corydalus cornutus (fig. 6.4a) is known as far south as Panama, from where a second, closely related species, C. armatus, continues into South America. The Sialidae ("alderflies") are represented by just 7 localized species in a single genus and are not discussed further here.

Like neuropterans, dobsonflies have two pairs of membranous wings with complete venation, although the multiplicity of spurious veinlets and cross veins found in the Neuroptera is lacking. Except for minor differences in the branching of veins and being slightly narrower, the fore wings are similar to the hind wings. The body is cylindrical, elongate, and somewhat soft and flexible. Legs are short and similar on each thoracic segment. In both the adults and larvae, the mouthparts are mandibu-late and with elements, especially the mandibles, strongly developed. Males of some species of Corydalus have extremely long, tusklike jaws (Glorioso 1981). All dobsonflies, except the lemon yellow Chloronia (Penny and Flint 1982), are brown to dull gray or black. Males of Platyneuromus (= Doeringia) have a flattened lateral expansion on the head behind the compound eyes.

The larvae (hellgrammites) (fig. 6.4b) are similar in body structure to the adults but are slightly flattened and have conspicuous fingerlike gills laterally on the abdomen. These gills may be bare or fringed, and there may be a tuft of accessory gill filaments at the base of most of the primary appendages. The last abdominal segment bears a pair of large prolegs, each with a lateral filament and large claws at the tips.

Dobsonflies are ubiquitous aquatic insects, generally associated with clean, cold, mountain streams. The adults remain near such streams and are rarely seen except when they come to lights at night or when flying, as they do occasionally on cool, overcast days or at dusk. Females attach their eggs in large, single-layered clusters to objects near or overhanging the water. These white, flattened masses are sometimes conspicuous on dark-colored boulders or tree trunks. The larvae are active predators, catching and eating a variety of other aquatic insects that they find under and around debris and rocks. They leave the water to pupate. Pupae have free, muscled legs and are able to walk and use their mandibles to bite in defense.

In the Peruvian Amazon region, dobson-fly larvae, devoured raw or cooked, are collected by the natives for food (Murphy pers. comm.). Called perros de agua, they are considered venomous and much feared in parts of Mexico.

The literature of the Latin American members of this order is reviewed by Flint (1977) and Penny (1981, 1982).

References

Flint, Jr., O. S. 1977. Neuroptera. In S. H. Hurlbert, ed., Biota acuática de sudamérica austral. San Diego State Univ., San Diego. Pp. 187-188.

Glorioso, M. J. 1981. Systematics of the dob-sonfly subfamily Corydalinae (Megaloptera: Corydalidae). Syst. Entomol. 6: 253-290. Penny, N. D. 1977. Lista de Megaloptera, Neuroptera e Raphidioptera do México, América Central, ilhas Caraibas e América do sul. Acta Amazónica 7(4) suppl.: 1-61. Penny, N. D. 1981. Neuroptera. In S. H. Hurlbert, G. Rodriguez, and N. Dias dos Santos, eds., Aquatic biota of tropical South America. Pt. 1. Arthropoda. San Diego State Univ., San Diego. Pp. 89-91. Penny, N. D. 1982. Neuroptera. In S. H. Hurlbert and A. Villalobos Figueroa, eds., Aquatic biota of Mexico, Central America and the West Indies. San Diego State Univ., San Diego. Pp. 280-282. Penny, N. D. 1983. Neuroptera of the Amazon Basin. Pt. 7. Corydalidae. Acta Amazónica 12: 825-837. Penny, N. D., and O. S. Flint. 1982. A revision of the genus Chloronia (Neuroptera: Corydalidae). Smithsonian Contrib. Zool. 348: 1—27.

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