CHRYSOPERLA PLORABUNDA (NEUROPTERA: CHRYSOPIDAE) LARVAE FEED DISPROPORTIONATELY ON THRIPS (THYSANOPTERA: THRIPIDAE) IN THE FIELD

Green lacewings (Neuroptera: Chrysopidae) are commercially available augmentative biological control agents. Despite centuries of recognition as beneficial insects (Darwin 1800), scant information can be found describing what lacewing larvae prey upon in the field when several different prey species are present (New 1975). I assessed the types of prey that Chrysoperla plorabunda (Fitch) larvae consume when they are released on peas, Pisum sativum L. (Fabaceae), in western Washington. In 1997, two field assistants and I made observations at three sites: the Rent's Due Ranch (RDR: 48°14′N, 122°22′W), an organic farm located just outside Stanwood, Washington, and two research farms (Sumner: 47°11′N, 122°13′W; and Fife: 47°12′N, 122°20′W) in the Washington State University extension station system. Planting dates differed among these sites; at RDR, peas were planted in the spring, whereas we planted peas at the Sumner and Fife farms in June and July, respectively. Despite this and other differences, the peas at each site harbor similar insect communities (unpublished data).

Laboratory hybridization in green lacewings (Neuroptera: Chrysopidae: Chrysoperla): evidence for genetic incompatibility

Courtship songs are an important reproductive barrier in lacewings of the genus Chrysoperla, so heterotypic matings should occur less readily than homotypic matings. In addition, if song morphs have become separate species, there may be some postzygotic isolation between song morphs. Two generations of crosses using sympatric P1 and P3 morphs of Chrysoperla plorabunda provide evidence for both hypotheses. In the first stage of the experiment, egg laying (an indication of mating success) was delayed by a week in heterotypic crosses compared with homotypic crosses, and hatching success of eggs from hybrid crosses was 16% lower than that from control crosses. In the second stage of the experiment, backcrosses involving P3 morph males or females were the least successful in mating. When pairs did mate, they did so a week later than in the other crosses. Thus, behavioral isolation delays heterotypic matings when females are not given a choice of mates. These results provide some genetic evidence that the song morphs of the C. plorabunda complex are biological species.

The status of the P2 song morph, a North American green lacewing of the Chrysoperla cornea species-group (Neuroptera: Chrysopidae)

The substrate-borne courtship song of the P2 song morph of Chrysoperla plorabunda is described. It is a tremulation signal, produced by rapid vertical oscillation (jerking) of the abdomen. Both sexes produce identical shortest repeated units (SRUs) and must duet with one another before mating. In each of five principal features of its song, the P2 morph is strikingly homogeneous throughout its broad geographical range in western North America; a stepwise multiple regression procedure shows that populations from the Pacific Northwest, central California, and southern California are acoustically identical. Recombination in subsequent laboratory generations has no effect on song variance, suggesting that the morph is stable and not of hybrid origin. The nominate form of C. plorabunda, here called P1, co-occurs with P2 at sites north of California and is morphologically identical with it. However, the songs of the two morphs differ significantly from one another in every feature; in particular, P2 volleys are longer and spaced farther apart than P1 volleys. Complicating the picture is a third cryptic song morph, P3, which co-occurs with P2 at most sites and produces a song characterized by even longer volleys. Hybrids produced in the laboratory between P1 and P3 have songs that superficially resemble those of P2, but which in fact are significantly different in most respects. The P2 song morph seems to be a cohesive genetic unit deserving recognition as a separate species.