PROC. ENTOMOL. SOC. WASH. 89(4), 1987, pp. 776-789 BIONOMICS OF MICROMUS POSTICUS (WALKER) (NEUROPTERA: HEMEROBIIDAE) WITH DESCRIPTIONS OF THE IMMATURE STAGES Department of Entomology, Auburn University, Alabama 36849. Abstract. -The egg and larva of Micromus posticus (Walker) are redescribed and illus- trated. While setal patterns appear similar for all instars, head capsule dimensions can be used to distinguish between instars. A key to the instars is provided. The life history of M. posticus was studied using Aphis gossypii Glover as prey. Laboratory-reared females survived an average of 6 1 days and males an average of 74 days. Adult female survivorship was 100% up to 25 days. Mean total egg production was 933.2 eggdfemale, with a maximum of 1484. Net reproductive rate was 461.3 females/female/generation, mean generation time was 56.3 days, intrinsic rate of increase was 0.153 females/female/day, doubling time was 4.5 days, and finite rate of increase was 1.17/individual/day. Laboratory and field observations in east-central Alabama indicated that females oviposited most often on fibrous material such as cotton fibers and spider mite webbing. Pupation in the field on cotton occurred within bracts on bolls and in folds of leaves. Charitopes mellicornis (Ashmead) and Anacharis melanoneura Ashmead together parasitized 6% of the M. pos- ticus larvae in an unsprayed cotton field. The Hemerobiidae continue to be over- er) has been collected in the eastern United looked despite the widely held belief that States from Massachusetts west to Minne- they are important predators. Withycombe sota and south to Florida and Texas (Car- (1 924) ranked them as one of the three most penter, 1940) and as far north as Manitoba, economically important Neuroptera fami- Canada (Batulla and Robinson, 1983). The lies in Britain. Balduf (1 939) considered the most common species of the genus (Car- hemerobiids the most important Neurop- penter, 1940), it is associated with a variety tera next to the Chrysopidae in controlling of different habitats including mixed forest soft-bodied agricultural pests. Although all (Batulla and Robinson, 1983), citrus groves hemerobiids are predatory, many are lim- (Muma et al., 196 I), pecan orchards (Edel- ited in habitat range or exhibit a prey spec- son, 1982), vineyards (Jubb and Masteller, ificity that limits their effectiveness (New, 1977), cotton fields (Whitcomb and Bell, 1975). However, some species do frequent 1964), potato fields (Mack and Smilowitz, low vegetation, and could be considered for 1980) and alfalfa (Smith, 1923). The pest use in many agroecosystems. prey of M. posticus include the cotton aphid, Among the species that New (1975) con- Aphis gossypii Glover, Aphis spiraecola sidered to be of agronomic importance were Patch, the green peach aphid, Myzus per- species of the genus Micromus. In the sicae (Sulzer), the black citrus aphid,, Tox- Nearctic region, Micromus posticus (Walk- optera aurantii (Fonscolombe). and Mnrm- VOLUME 89, NUMBER 4 777 siphum sp. (Selhime and Kanavel, 1968), formalin preservative, rinsed in distilled the cabbage aphid, Brevicoryne brassicae water, air dried, mounted on aluminum (L.), and eggs of the imported cabbage- stubs with double-coated cellophane tape, worm, Pieris rapae (L.) (Cutright, 1923), and coated with gold-palladium alloy in a yellow pecan aphids, Monellia caryella sputter coater. Egg ultrastructure and ultra- (Fitch) and Monelliopsis nigropunctata structure measurements of these eggs were (Granovsky) (Edelson, 1982)and Uroleucon determined using an ISI-SS40 scanning ambrosiae (Thomas) (Batulla and Robin- electron microscope (SEM) with an accel- son, 1983). erating voltage of 5 kV. Photographs were Smith (1922, 1923) and Cutright (1923) taken with Polaroid 5 5 film. Measurements provided the first life history accounts of M. were recorded in millimeters (mm) with posticus. Smith (1 922) observed hatching means followed by ranges in parentheses. and (1923) briefly described the larval in- Larval morphology. -Larvae were ex- stars. Cutright (1923) determined consump- amined under a Zeiss compound micro- tion rates of the larvae and included notes scope, and measurements were made with on preoviposition time, fecundity, and adult an ocular micrometer. Larvae were ob- longevity. Selhime and Kanavel (1968) tained from the laboratory colony and were reared M. posticus on a variety of aphids at preserved and mounted on slides as de- 26.67"C and recorded developmental time. scribed by Wilkey (1 962). Setal numbers are They determined a fecundity of 509 eggs for given for each half of the body. Occasion- a single field-collected female. ally, setal pattern is expressed as a formula. Identification of the Hemerobiidae con- For example, the setal pattern 2-1-2 indi- tinues to be based primarily on adult mor- cates one long and one short seta together, phology (e.g. MacLeod and Stange, 198l), a single long seta, and one long and one while other stages are frequently over- short seta together from the midline to the looked. The potential of many hemerobiids lateral margin. Length of the setae (long or as biological control agents is also over- short) is relative to other setae of the same looked. The purpose of this study was to segment being described. Short setae are ap- provide morphological descriptions of the proximately one-half or less the length of egg and larval stages of M. posticus and to long setae. Measurements were recorded in better qualify and quantify various aspects millimeters (mm) with means followed by of its life history. ranges in parentheses. Life table. -Larvae reared from eggs were checked daily for molt to the next instar, Larval and adult M. posticus were ob- cocoon formation, and pupation. Upon tained by rearing eggs and larvae collected eclosion, adult females were transferred in- from a cotton field near Tallassee, Alabama. dividually to 60 x 20 mm petri dishes. A Larvae were caged in 50 x 9 mm plastic single male accompanied each female. Each petri dishes and provided daily with cotton mating pair was supplied daily with fresh aphids obtained from the field or green- cotton aphids and a ball of cotton saturated house. Voucher material of adults and lar- with 10% honey water. A portion of loose vae of M. posticus is deposited in the Au- cotton fibers was supplied as an oviposition burn University Entomological Museum. site. Females were checked daily for ovi- Egg morphology. -Eggs were measured position and survivorship. Eggs were re- with an ocular micrometer using a Wild ste- moved and counted and fresh cotton fibers reoscope to determine length and width. For were placed in the cage. Occasional samples examination with the scanning electron mi- of eggs were saved for rearing to determine croscope, other eggs were removed from 10% time to egg hatch. Dead males were replaced 778 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON Figs. 1-3. SEM photographs of Micromus posticus eggs. 1, Habitus (arrow indicates side of attachment to substrate) (97 x). 2, Anterior pole (469 x). 3, Micropyle (939 x). with live ones when necessary. All cages were assumed to be 50:50. This assumption is housed in a rearing room at 28°C and 70- supported by our determination of the sex 80% RH with a 14L: 1OD photoperiod. ratio of field-collected individuals and the A survivorship and fertility (= number of findings of Deyrup and Deyrup (1978), who offspring produced) table was constructed reported rearing nearly equal numbers of for adult females by determining for each both sexes from field-collected pupae of five day, or age interval (x), the proportion of species of hemerobiids. Life table statistics surviving individuals (1,) and the mean were calculated as follows: R,, the net re- number of female progeny per surviving fe- productive rate, is the sum of the products male (m,). The sum of the mean develop- lx*m,calculated for each age interval; G, the mental times of eggs, larvae, and pupae was generation time, is the sum of the products used to estimate the age at which adult eclo- l,*m,*x divided by R,; r, the innate capacity sion occurred. Egg survival was recorded as for increase, was calculated by substituting 100% since rearing of eggs for develop- values of r into the equation: Z (lx*mx*e-rx)= mental time, colony maintenance, and vi- 1 until equilibrium was reached; and A, the ability checks indicated complete egg hatch. finite rate of increase, was calculated as er. Due to exclusion of cannibalism, disease Field observations. -From July-Septem- and natural enemies, survivorship was also ber 1984, field observations of the life his- 100% for larvae and pupae. Sex ratio was tory of M. posticus were recorded from an VOLUME 89, NUMBER 4 779 unsprayed cotton field 3.2 km S of Tallas- .12) long, .09 mm (.08-. 1 1) wide; pedicel see, Elmore Co., Albama, which was heavily .99 mm (.93-1.02) long, .043 mm (-037- infested with cotton aphids. The field was .049) wide; flagellum .32 mm (.30-. 34) long sampled at the end of the growing season gradually tapering to a long apical bristle. (1 September) to determine density of co- Pedicel and flagellum with irregular annular coons per plant. Density was estimated by sclerotizations. Cervix: Venter with 3 small visually sampling 50 plants chosen at ran- anterolateral setae, 3 long median setae in dom, 10 in each of the four corners and in vertical row, 3 long median setae in oblique the center of the plot. row, 2-4 long lateral setae; dorsum with posterior row of 3-4 long setae, 3-4 sub- RESULTS median setae in vertical row, 2-3 long an- teromedial setae. Prothorax: Anterior sub- Descriptions of immature stages segment: Venter with 3 short setae near Egg.-(n = 15): Length .91 mm (38-.96), anteromedial margin, 2 short median setae, width .42 mm (.38-.46).