Hosts or Prey
A wide variety of small, soft-bodied insects and mites
Adults are soft-bodied and have 2 pairs of hairy, membranous wings that at rest are held rooflike over the body. The body and wings are commonly dark to light brown. Some species have a blackish or yellow body or become grayish-brown or spotted when overwintering. Adults have long slender antennae and at rest most species from head to wing tip (excluding antennae) are 1/5 to 2/5 inch (5–10 mm) long.
Eggs are elongate-oval and about 1/25 inch (1 mm) or less in length. They are commonly gray, pink, or whitish and have a finely pitted surface. Eggs can occur openly in colonies of prey, but also around buds, in crevices and pits of bark, or on twig crotches or tips where they are easily overlooked.
Larvae are elongate, flattened, and tapered at the tail and have distinct legs. They are 1/3 inch (8 mm) or less in length and resemble tiny alligators. Coloration on top is commonly cream, gray, or whitish with two, lengthwise, brown or reddish stripes or rows of spots. They have prominent, paired, tubelike mouthparts that curve inwards towards the tip.
Pupation occurs in a loosely woven, oblong or spherical, silken cocoon. The insect's body is partly visible through the pale fibers.
Brown lacewings (Hemerobiidae) and green lacewings (Chrysopidae) resemble each other as both adults and larvae. Among California species the adults and last instars of brown lacewings average about one-half the length of green lacewings.
Adult brown and green lacewings are not reliably distinguished by color. For example adults of some species of green lacewings are normally brown, grayish, or reddish and some normally green species become brown during late fall through early spring. Whether costal cross veins are forked (Y-shaped) reliably distinguishes the adults.
Larvae of brown and green lacewings are distinguished by an appendage (empodium) between the pair of tarsal claws on the end of feet. Unlike green lacewings, brown lacewing larvae appear to have a prominent neck because the first abdominal segment (prothorax) is elongated in comparison with the second and third segments with legs.
Larvae of both groups seek prey in a wandering manner, commonly turning their body and moving in irregular circles or semicircles. Larvae of brown lacewings additionally jerk or wriggle their head from side to side, left and right when viewed from above. Larvae of green lacewings orient their head mostly forward, in the direction of their body movement.
Eggs of brown lacewings are about the same color, shape, and size as those of syrphids and both can occur together. Brown lacewing eggs have a distinct, projecting, short disk or knob (micropyle), visible at the right end of the pictured egg; this feature (an opening for sperm) is inconspicuous on syrphid eggs, resembling a discolored spot. In comparison with brown lacewings, the surface markings on syrphid eggs are more prominent.
Lacewings develop though four life stages: egg, larva, pupa, and adult. Adult females lay eggs singly near colonies of prey on buds, leaves, and succulent stems. After hatching, larvae develop through three, increasingly larger instars before pupating. Pupae occur on plant surfaces or under loose bark.
All stages can occur throughout the year in places without cold winters; egg laying may cease and adults become less active and their coloration may change overwinter. Especially in locations with cold winters, overwintering is mostly as inactive, last instars (prepupae) or pupae in silken cocoons in protected locations, such as bark crevices.
California species have several generations per year. Adults of Hemerobius pacificus live about 10 weeks during which females lay about 600 to 700 eggs. One generation is completed in about 6 weeks when temperatures average 65ºF.
Adults and larvae can be found in gardens and field crops, but they occur mostly on shrubs and trees, such as tree crops and woody plants in landscapes and natural areas. Brown lacewings in California are common in coastal areas, but not interior locations with hot summers. Adults and larvae are active mostly during dusk through dawn and overcast conditions. Adults are observed when drawn to lights at night or taking flight after plants on which they rest are disturbed.
Larvae use their prominent, sharp mouthparts to impale prey and suck the body contents. Aphids, mealybugs, and mites are common prey. Other prey includes eggs of insects and mites, lace bugs, leafhoppers, psyllids, scales, small caterpillars, thrips, and whiteflies.
At least 5 genera and 31 species of brown lacewing occur in California. These include Megalomus and 6 or more species each of Hemerobius, Micromus, Sympherobius (e.g., Barber brown lacewing), and Wesmaelius (=Boriomyia). Hemerobius pacificus is the most common species and found mostly in coastal areas.
- Biology of Adult Hemerobius pacificus, UC Berkeley, Environmental Entomology
- Biological Control and Natural Enemies of Invertebrates, UC Integrated Pest Management Program
- Family Hemerobiidae - Brown Lacewings, BugGuide, Iowa State University
- Neuroptera, Hemerobiidae (Westwood 1840): Description & Statistics, UC Riverside
- Neuroptera (Lacewings and their Relatives), UC Irvine
- Species Catalog of the Neuroptera, Megaloptera, and Raphidioptera of America North of Mexico (PDF), California Academy of Sciences
- Phylum: Arthropoda
- Class: Insecta
- Order: Neuroptera
- Family: Hemerobiidae