common name: brown lacewings (of Florida)
scientific name: (Insecta: Neuroptera: Hemerobiidae)

Introduction - Distribution - Biology - Identification - Detection and Survey - Key to Genera and Species of Brown Lacewings of Florida - Selected References

Introduction

Brown lacewings are small to medium-sized insects (forewing length 3 to 9 mm in Florida) which are predaceous both as adults and larvae. They prefer soft-bodied insects such as aphids, mealybugs, and also insect eggs. Because of the longevity of the adults (at least months in some species), voracious appetites (for example, Micromus posticus (Walker) larva consumed an average of 41 aphids during its life (Cutright 1923), and high reproductive capacity (one female Hemerobius humulinus Linnaeus can lay 460 eggs (Smith 1923), they are useful biological control agents. Some species have been utilized for this purpose, but limited work has been done. In Texas, Sympherobius barberi Banks is being mass reared for control of citrus mealybug (Hart, personal communication). Florida has a small fauna of 10 species in four genera, and the present circular provides keys to identification of the adults of our species.

Distribution

Of the 58 North American species, all are found in northern Florida and three of these (S. occidentalis, S. gracilis, B. fidelis) are here recorded for the first time for Florida (all from Gainesville). B. speciosa has not been rediscovered in Florida since Carpenter (1940) recorded it from Sanibel Island. S. amiculus, S. barberi and H. stigma are known as far south as Highlands County, whereas both species of Micromus are found throughout peninsula Florida (M. subanticus also in the Keys and in the Caribbean). H. humulinus and H. stigma are Holaretic, but the former is relatively uncommon in Florida.

Biology

Females lay non-stalked eggs, usually singly or in small groups. There are three larval instars. The 1st instar is active in all species. It can run fast, moving the head from side to side as it moves. In Sympherobius spp. and especially Boriomyia spp., the later instars are relatively immobile. A white cocoon of double structure (outer loose thread, inner compact structure) is constructed in protected areas. Most groups appear to prefer aphids, but Sympherobius spp. may prefer coccid insects (especially mealybugs). Spiders are considered one of the most important natural enemies of lacewings. References on biology for species occurring in Florida are: Cutright (1923 - Micromus posticus), Smith (1923 - Sympherobius amiculus, Hemerobius humulinus, H. stigma, M. posticus; 1934 - S. barberi), and MacLeod (1960 - Boriomyia fidelis).

Identification

Adults have a wing venation with two or more branches arising directly from the fused stem of R1 + Rs (Figure 1). The wing membrane has microtrichia (contrasted with Chrysopidae), ovipositor not exerted, antenna moniliform and front legs not raptorial.

adult

adult

Larvae have jaws which are fairly straight basally and curved apically, mandibles lacking teeth along medial margin, pretarsal claws lack a trumpet-shaped empodium (a spine or lobelike process) (except 1st instar), and are not trash bearers, in contrast to many statements in the older literature (e.g., Comstock 1925, Introduction to Entomology, p. 297).

Detection and Survey

Adults are commonly attracted to lights. Adults and larvae can be found by beating or sweeping plants, especially oaks and pines and plants with high aphid infestations such as alfalfa. Brown lacewings resemble green lacewings (Chrysopidae) but are brownish and are less common. There are 58 North American species. The eggs are laid on plants, but not stalked. The brown lacewing larvae differ from green lacewing larvae in that they do not possess tubercles (a small knoblike or rounded protuberance). Both adults and larvae prey on aphids, other soft-bodied insects and mites.

larva

Key to Genera and Species of Brown Lacewings of Florida

(Wings and male terminalia after Carpenter 1940)

1. Forewing with costal area quite narrow at base, lacking a recurrent humeral vein (Figures 1, 2) . . . . . Micromus Rambur . . . . . 2
1'. Costal area of forewing much broader basally (Figure 7), often abruptly broadened (Figures 4, 10) and always with a recurrent humeral vein . . . . 3

2 (1). Inner gradate veins of forewing much more than their lengths apart (Figure 1); male terminalia as in Figure 3a . . . . . Micromus subanticus (Walker)

2'. Inner gradate crossveins of forewing at most only their lengths apart (Figure 2) ; male terminalia as in Figure 3b . . . . . Micromus posticus (Walker)

3 (1'). Forewing with three or more branches arising from the fused stem of R1 and Rs distal to separation of MA (Figure 4); maxillary palpus 5-segmented, labial palpus with three segments . . . . . Boriomyia Banks . . . . . 4
3'. Forewing with fewer than 3 branches arising from R1 + Rs distal to separation of MA (Figure 7), most-basal branch arising from R1 + Rs often stalked with MA (Figure 10); maxillary and labial palpi with a small peg-like apiculus so that they appear 6- and 4-segmented respectively (Figure 16) . . . . . 5

4 (3). Male paramere with lateral process not forked distally (Figure 6a); forewing usually lacking dark brown spots around distal crossveins between branches of Cu (although light-brown cloudings of the membrane adjacent to the crossveins may be present), usually with 2 broad transverse light-brown bands paralleling the inner and outer series of gradate crossveins . . . . . Boriomyia fidelis (Banks)

4'. Male paramere with lateral process forked distally (Figure 6b); forewing usually with discrete dark brown spots around distal crossveins of Cu and the M-Cu crossvein, pale brown maculations sometimes present elsewhere, especially around the inner and outer series of gradate crossveins . . . . . Boriomyia speciosa (Banks) 5 (3'). Forewing with five or more outer gradate veins (Figure 7); forewing without crossvein between MP and MA . . . . . Hemerobius Banks . . . . . 6
5'. Forewing with four or fewer outer gradate veins Figure 10); MP and MA connected by crossvein shortly after origin of former (Figure 10) . . . . . Sympherobius Banks . . . . . 7

6 (5). Pronotum and mesonotum with broad yellow stripe; upper process of male ectoproct forked distally (Figure 8) . . . . . Hemerobius humulinus Linnaeus

6'. Pronotum and mesonotum with, at most, a narrow median stripe (this is often absent); mesonotum without defined stripe (Figure 17); upper process of male ectoproct not forked (Figure 9) . . . . . Hemerobius stigma Stephens 7 (5'). Forewing without radial crossvein; male ectoproct with three processes, none bifurcate; upper process shorter than lower one (Figure 11) . . . . . Sympherobius barberi Banks 7'. Forewing with radial crossvein (Figure 10, "rc"); male ectoproct either with two processes, or, if three, one is bifurcate or the upper as long as lower one . . . . . 8

8 (7'). Forewing vein Cul forks nearer hindmargin than to crossvein m-cu; male ectoproct with two processes . . . . . Sympherobius occidentalis Fitch

8'. Forewing vein Cul forks at or near crossvein m-cu (Figure 10); male ectoproct with three processes . . . . . 9

9(8'). Most cells of forewing pale in centers and along margins of veins; veins nearly uniformly dark with at most slightly darker points at bases of setae; male ectoproct with lower process bifurcate (Figure 13) . . . . . Sympherobius gracilis Carpenter

9'. ells of forewing membrane hyaline with irregular gray or brown blotching; veins pale with dark spots at setal bases (especially along Cu and A) and where crossed by membrane maculations; male ectoproct without bifurcate process (Figure 14) . . . . . Sympherobius amiculus (Fitch)

Selected References

Authors: Ellis G. MacLeod and Lionel A. Stange, Florida Department of Agriculture and Consumer Services, Division of Plant Industry
Originally published as DPI Entomology Circular 227.
Drawings: Division of Plant Industry
Photographs: Lyle Buss, University of Florida; and Ken Gray, Oregon State University
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-225
Publication Date: August 2001. Latest revision: June 2005.
Copyright 2001-2005 University of Florida

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