CARIBBEAN FOOD CROPS SOCIETY

30 THIRTIETH ANNUAL MEETING 1994

ST. THOMAS, U.S.V.I.

Vol. XXX ENTOMOPHAGOUS AS AGENTS FOR BIOLOGICAL CONTROL OF PESTS OF COLE CROPS IN

M. M. Alam1, A. Mansingh2 and W. Fielding3

' Agricultural Research and Development Institute (CARDI) 2PPRG, Department of Zoology, UWI, Mona, Kingston 7 'Ministry of Agriculture. Boldes Agricultural Experimental Station

ABSTRACT

Fifteen species of belonging to eight different families have been found feeding voraciously on larvae of diamondback moths (DBM), Plutella xylostella; cabbage looper (CL), Trichoplusia nr, army-worms (AW's), Spodoptera latifascia: a pyralid (P), Pilemia periusalis and an unidentified noctuid (N). The population of spiders remained constant in unsprayed fields, ranging from 2/nr of L. atlantica, 4/m2 of L. fusca to 0.08/m2 of others. The spiders were generally most susceptible to diazinon > diaphenthiuron > prophenophos sprays. The spiders showed no preference for the host larvae in multiple-host species diet. Feeding activity that was generally cyclic-intense feeding for a couple days was followed by a similar period of little feeding. The spiders could consume daily about 0.8 to 18.3,0.1 to 1.7 or 0.1 to 1.7 mature larvae of DBM, CLor AW, respectively. Spraying with prophenophos, diazinon and diaphenthiuron reduced the field population of spiders by 43 to 82%, 80 to 100% and 55 to 97%, respectively.

INTRODUCTION

Potentials of biological control as an adjunct to integrated management of vegetable pests has never been explored in Jamaica, though Forbes and Mansingh (1988) had reported high incidences of parasitism in the field populations of diamondback moths (DBM), Plutella xylostella (L.). In fact, they recorded the larval parasites, Diadegma insulare (Cresson) and a larval-pupal parasite, Oomyzus (=Tetrastichus) sokolowskii (Kurdj.) and a new species of a hyperparasite of Diadegma, Spilochalcis sp. for the first time in the Caribbean. Later, Alam (1992) found two more species of DBM parasites and three new species of hyperparasites in the island. Furthermore, three exotic specics of parasites, Cotesia plutellae (Kurdj.), Trichospilus diatraeae C. & M. and O. sokolowskii, which were introduced during 1988-89 were found fully established in Jamaica. Jamaica is also rich in other natural enemies of crucifer pests- eight species of insect predators, viz. Coleomegilla maculata (DeGeer), Cycloneda sanguinea (L.), Hippodamia convergens Guerin (Coccinellidae). Belonuchus gagates (Erichson) (Staphylinidae), Toxomerus dispar (F.),Toxomerus watsoni (Curran) and Pseudodoros clavatus (F.) (Svrphidae), Ceraeochrysa claveri Navas (Chrysopidae) and three species of parasitic fungi, Beauveria bassiana, Hirsutella sp. and Paecilomvces fumosoroseus (Alam, 1992). Further surveys of vegetable growing areas in Jamaica revealed the presence of 15 species of spiders predating on crucifer pests. The present report explores their population fluctuations, biological control potential and susceptibility to pesticides.

MATERIAL AND METHODS

Collections of spiders

Spiders were collected from unsprayed experimental cabbage fields at Douglas Castle in central Jamaican (elevation, 610 m), Castle Kelly (elevation, 457 m), and Bodies Agricultural Experimental

289 Station (elevation 18 m), during 1992-94. Ground spiders were collected by disturbing the leaf litter in the field, orb weavers from either webs or the cabbage leaves and the jumping and crab spiders from the ground and cabbage plants. These spiders were directed gently into individual glass/plastic vials (2.5x10 cm) with a strip of cabbage leaf. The spiders were identified by Dr. G.B. Edwards (Curator, Arachnida and Myriopods, Florida State Collection of , Division of Plant Industry, P.O. Box 1269, Gainesville, Florida 32602).

Population fluctuations

Populations of spiders in two unsprayed cabbage fields were recorded at four weekly intervals of three successive crops, between May 1993 and February 1994, al Douglas Castle. Fields were divided into the peripheral and middle zones and each zone was further subdivided into five randomized 1 m2 blocks for sampling populations.

Food consumption

The host preferences, the amount of food consumed and the patterns of food consumption by the spiders were studied by feeding all but four species individually in vials on single host species diet comprising of mature (last two instars) larvae of P. xylostella, T, ni,S. latifascia, P periusalis and an unidentified noctuid species, or on a multiple-hosl species diet, which included the larvae of the host species. Hentzia sp., C. pulcherrima, Habronathus sp., Oxyopes sp. and T. gonygaster, were always fed on the first two instars of the host larvae as they could not handle and feed on larger larvae. Each spider was provided with a pre-weighed diet of the host larvae, which was replaced every 24 hours for one week. The unconsumed larvae were weighed, the amount consumed during the preceding 24 hours was estimated. The daily pattern of food consumption was studied on five of the most common specics of spiders found in the field. Five individuals of each species were provided daily with pre-weighed diet of multiple host species. The experiments were conducted for 36 to 80 days, depending upon the survival of the species under captivity A biological control index (BCI) of each species was calculated by multiplying the mean population/ m2 by the mean number of larvae of DBM consumed by the spider per day

Effect of Insecticides

Preliminary observations in various fields/farms, which were regularly sprayed with insecticides, indicated very low populations of the most predominant species of spiders. A study was therefore undertaken to evaluate the effect of selecron (Profenofos)EC 500 at the rate of 3.1 mL/L; basudin (Diazinon) EC 60, at the rate of 0.51/ha; and pegasus (Phio urea) SC 500, at the rate of 3.7-5.01/ha in fields (about 0.5 ha) which were sprayed by farmers using a knapsack sprayer. Unsprayed fields were adjacent to each sprayed field. The treated and control fields were randomly divided into five 1 m2 plots and the population of spiders counted one week after spraying.

RESULTS AND DISCUSSION

Spider species

Fifteen species of spiders belonging to eight different families (Table 1) are quite widespread in Jamaica, as they were recorded from each of the three cabbage growing areas of the island. The orb- weaver (Araneidae) was the largest family with three species, followed by Lycosidae, Oxyopidae, Argiopidae, and Salticidae, with two species each, and Heterapodidae and Tetragnathidae,

290 with one species each. All these species are widespread also in the tropics and neotropics, including southern USA and (Levi and Levi, 1990).

Population fluctuation

All but four species of spiders were always found in the study areas, distributed evenly in the peripheral and middle zones of the cabbage fields (Table 2). L. atlantica, L.fusca, T. gonygaster, A. trifasciata and Habronathus sp. were the most abundant species with a mean monthly population of 2.0, 2.0. 1.2, 1.03 and 1.02 spidcrs/m2. The mean monthly populations of seven other species ranged between 0.42 and 0.021 spiders/m2. Among the least abundant species was L regnyi (0.19/ m2). N. neothcis (0.15/m2), G. canceriformis (0.12/m2) and H. venatoria (0.06/m2). The last two species were conspicuous by their absence during post-rainy seasons, particularly during winter months. Generally the population of spiders, particularly the orb-weavers, in the field depended upon atmospheric dynamics (Greenstone et al.. 1991), vegetation, (MacArthur, 1969, Pianka, 1966), and the host population (Greenstone, 1984). Both these factors were constant in our study fields to account for difference in the populations of different species. Greenstone et al (1987) had found a correlation between mass of ballooning spiders and their frequency distribution in Missouri (USA) and New South wales (Australia); more than half of the spiders caught were 0.6mg and 85 to 94% were <1 mg in weight. Our data in Table 3 reveals no general mass frequency relationship. The heaviest spider, P. viridens and the lightest ones (Hentzia sp. and Oxyopes sp.) were always the least abundant species. Likewise, the moderately heavy species, L.fusca (0.15 g) and L. atlantica (0.01 g) were the most abundant spiders (2/m2), while A. argentata with smaller weight (0.11 g) was the least (0.2/m2) abundant species. The population densities of different species may be a phenomena of preying modes, and weight of the spider. Indeed, among the orb-weavers, .4. argentata, A. trifasciata and T. gonygaster, there was no overall correlation between spider weight and population (Table 3). Among jumping and hunting spiders, however, the heaviest (P. viridens) and the lightest (Oxyopes sp. and Hentzia sp.) appear to have the least, while the medium sized (0.01 and 0.15 g) have the maximum advantage in frequency distribution. It may be pointed out that because spiders have metabolic and anatomical adaptation (Greenstone, 1978; Greenstone and Bennett, 1964) which reduces their energy requirements and buffer them against energy availability, "the marginal scare resources become adequate" (MacArthur, 1969) and influence their frequency distribution. The orb-weaver population is dependent upon structural diversity of the habitats, which is required by spiders for physical support (MacArthur and MacArthur, 1969). Web spider density is highly correlated with vegetation and tip height diversity; prey availability is not a significant factor (Greenstone, 1984).

Food preferences and consumption

The spiders showed no preference when fed on multiple host diet. Apparently, the nearness and activity of the larvae prompted response from the predators. The spiders were more interested in satisfying their appetite and consuming a certain amount of food (Table 4), rather than discriminating among the host species. It is pertinent to note that some spiders do exercise preferential feeding on insects, depending upon developmental stage, size and odor of the prey. Two species of Lycosidae feed preferentially on insects in California (Greenstone, 1980). Several web-spider species were found to consume Ephemeropteron and Dipteron, which were 6 and 5 mm in length, but on other insects which were less than 4 mm in length (Greenstone, 1984). Only < 2 mm long Orthoptera and Thysanoptera could be consumed. The amounts of food consumed varied greatly among the spiders, the most voracious feeders, H. venatoria, L. atlantica, P. viridens and L.fusca, were consuming about 0.165, 0.137, 0.126, and

291 0.124 g of food/day respectively. If fed on single species diet, the number of the last two instar larvae of DBM consumed by the four species of spiders would range from 18.3 to 13.8, while only about 0.69 to 0.52 g of the larger noctuid larvae would be eaten (Table 4). The other seven species could consume from about 0.8 to 6.7 DBM larvae/day, but only parts of other larvae. Muckenfus et al (1992) had reported increased consumption of DBM larvae by the spider Pardosa milvinna (Hentz), when host density increased from 1 to 8 larvae/cage and with time. In our in vitro studies, no such correlation was evident as the food supplied was always more than the ability of the spiders to consume. Greenstone (1978) demonstrated that free living wolf spider tends to prey on species in proportion, which optimizes the proportions of essential amino acids they provide in the diet, and suggested that this could account for the differences in the amount of different prey species consumed by the spiders. This is obvious that all the host larvae satisfied equally the amino acid and other nutritional requirements of the spiders. In Jamaica an interesting correlation between the weight of the spider and the weight of the food consumed is presented in Table 5. Among the four species which could prey upon only first and second instar larvae, Habronathus sp. was the most voracious followed by Hentzia sp., C. pulcherrima and T. gonygaster, respectively. Detailed studies on the pattern of food consumed by six different spiders, rangi ng from most to least voracious species revealed that (1) intense feeding activity for a day or two was usually followed by a couple of days of significantly (p>0.01) low levels of food consumption, and (2) some species, e.g., L. atlantica (Fig. 1), H. venatoria (Fig. 2), P. viridens (Fig.3), L.fusca (Fig.4) and Habronathus sp. (Fig. 5) showed distinct periods of intense and moderate feeding, and (3) the least voracious, Hentzia sp. consumed at uniform level, showing no significant difference (P>0.01) during most of its life (Fig. 6). Apparently the feeding behavior of the spiders has evolved foraging and physiological adaptation for overcoming uncertainty of adequate food availability in their habitat. Like insects during dormancy, the spiders depress metabolic rates below resting levels during periods of starvation (Anderson, 1978; Humphreys, 1977). This metabolic variability has a net effect on energy loss for spiders than for other of their size and tropic position (Greenstone, 1978). Furthermore, spiders tend to optimize acquisition of nutrients, rather than maximize energy intakes (Greenstone, 1979). The pattern of fluctuations in the intake of food by the Jamaican spiders maybe an inherent, environmentally induced adaptive strategy for the optimization of food intakes.

Effect of insecticides

Selecron, pegasus and basudin sprays reduced the field populations of seven species of spiders by 43 to 82 %, 82 to 100% and 55 to 97 % respectively, depending upon the species of spiders and the insecticides (Fig. 7, Table 6). The reduction in the predator populations resulted in significant (p>0.05) build up of the DBM, CL, AW populations (Table 4). A similar increase in DBM population inpyrethroid treated plots was reported by Muckertfuss etal., (1992) and attributed to the mortality of Diadegma insulare (Cresson) and P. milvinna due to the insecticide.

Biological Control Potential

Spiders with phenomenal densities are the most constant components of our environmental complex (Dondale, 1970). These features "would make spiders the most important group of insectivore in some terrestrial habitat" (Greenstone and Bennett, 1980). Indeed our data endorse these statements, as far as Jamaican cabbage fields are concerned. L. atlantica with biological control potentia: index (BCI) of 336 is the most promising natural enemy of DBM, followed far behind by L.fusca (27.6) > Ilabronathus sp. (4.8) > P. viridens (4.3) > A. trifasciata (1.5) and others (0.13 - 1.2). However, the use of insecticides would nullify the advantage of the natural enemies Appropriately timed augmentation of field population of spiders

292 with a greenhouse cultured population aught to eliminate the use of insecticides. Further investigations on the colonization of insecticide-treated cabbage fields by the spiders would be required for dev eloping an integrated management strategy of the cabbage pests.

Table 1: Species of spiders collected from fields in three cabbage growing areas of Jamaica.

Common Name Family species

Orb-wcavers Araneidae Eriophora sp. Gasteracantha canceriformis (L.) Neoscona neothcis (Petrunt.) Argiopidae Argiope argentata (Fab.) Argiope trifasciata (Forskal) Wolf/Ground spiders Lycosidae Lycosa atlantica Marx Lycosa fusca (Keyserling) Lynx/Hunting spiders Oxyopidae Oxyopes sp. lineatipesl (Koch) Peucetia viridens (Hentz.) Jumping Spiders Salticidae Habronathus sp. Sensu Latu Hentzia sp. vittatal (Keyserling) Combfooted or Cobweb spiders Theridiidae Chrysso pulcherrima Malls Leitao gonygaster (Simon) Hunting Spider Heteropodidae Heteropoda venatoria (L.) Four Jawed Spiders Tetragnathidae Leucauges regnyi (Simon)

Table 2: Population of different species of adult spiders/m2Douglas Castle, Jamaica, between May 1994 and February 1994.

Population of spiders/m2 at each month in 1993 and 1994.

Species M J J A S O N D J F

L. atlantica 2.4 2.1 1.8 1.2 1.9 2.2 1.7 2.9 3.2 1.6 L. fusca 2.3 1.6 1.2 1.3 1.7 1.8 1.8 2.9 3.1 2.1 T. gonygaster 1.2 1.4 1.1 0.7 1.0 1.4 1.1 1.3 1.4 1.2 A. trifasciata 0.8 0.7 0.8 0.5 0.9 1.0 0.7 1.0 1.6 2.3 Habronathussp. 1.0 0.9 0.6 0.7 1.6 1.2 1.0 1.1 1.2 0.9 C. pulcherrima 0.3 0.4 0.4 0.3 0.4 0.4 0.5 0.5 0.5 0.5 Hentzia sp. 04 0.4 0.2 0.3 0.3 0.4 0.4 0.5 0.4 0.6 L. regnyi 0.4 0.2 0.2 0.2 0.1 0.3 0 0.3 0.1 0.1 P. viridens 0.2 0.1 0.2 0.1 0.1 0.1 0.5 0.4 0.2 1.2 Oxyopes sp. 0.4 0.4 0.5 0.1 0.3 0.1 0.3 0.1 0.5 0.3 Eriophora sp 0.2 0.4 0.3 0.3 0.2 0.4 0.2 0.1 0.1 0.3 A. argentata 0.3 0.2 0.2 0.2 0.1 0.2 0.1 0.1 0.3 0.4 N. neothcis 0.4 0.1 0.2 0.1 0.1 0.2 0.1 0 0.2 0.1 G. canceriformis 0.3 0.3 0.1 0 0.3 0.1 0 0 0 0 H. venatoria 0.1 0.1 0.1 0.1 0.1 0.1 0 0 0 0

293 Table 3: Spider weight and population,

Species Foraging Mode Wt.(g) ±SE Population/m2

P. viridens Hunting 0.30 ±0.024 0.3 L.fusca Hunting 0.15 ±0.016 2.0 A. argenlata Orb-weaver 0.11 ±0.016 0.2 L. atlantica Hunting 0.10 ±0.027 2.0 A. trifasciata Orb-weaver 0.03 ±0.004 1.0 Habronathus sp. Jumping 0.01 ±0.001 1.0 Oxyopes sp. Hunting 0.007±0.0007 0.3 Hentzia sp. Jumping 0.004±0.0002 0.4 T. gonygaster Orb-weaver 0.004±0.0002 1.2

Table 4: Estimated consumption of different species of host larvae by various species of spiders in Jamaica in captivity.

Estimated numbers of different1 species2 of larvae consumed/spider/day Species Consumption DBM CL AW P N (g)±SE

H. venatoria 0.17±0.02 18.3±1.0 1.7±0.01 1.7±0.09 2.2±0.004 0.7±0.002 L. atlantica 0.14±0.01 15.2±0.6 1.3±0.01 I.4±0.06 1.8±0.003 0.6±0.003 P viridens 0.13±0.01 14.0±0.4 1.2±0.0t 1.3±0.1 1.7±0.001 0.5±0.001 L.fusca 0.12±0.02 13.8±0.5 1.2±0.02 1.3±0.12 1.6±0.01 0.5±0.001 A. argentata 0.06±0.001 6.7±0.1 0.6±0.003 0.6±0.02 0.8±0.003 0.3±0.002 A. trifasciata 0.06±0.002 6.4±0.2 0.6±0.005 0.6±0.02 0.8±0.002 0.2±0.004 Habronathus sp." 0.04±0.003 4.0±0.06 0.4±0.01 0.4±0,06 0.5±0.001 0.2±0.004 Hentzia sp." 0.03±0.002 3.1±0.06 0.3±0.00l 0.3±().05 0.4±0.001 0.00±0.001 C pulcherrima' 0.01±0.0001 1,4±0.03 0.1 ±0.004 0.1±0.02 0.2±0.02 0.00±0.00 Eriophora sp. 0.01±0.0004 1,6±0,1 0.1 ±0.004 0 2±0.07 0.2±0.(XM 0.06±0.002 G.canceriformis 0.01±0.0001 I.1±0.0I 0.1 ±0.0002 0.1 ±0.02 0.13±0.02 0.04±0.001 T. gonygaster' 0.008±0.002 0.9±0.06 0.1 ±0.02 0.1 ±0.01 0.1±0.01 0.03±0.00 L. regnyi 0.008±0.0001 0.9±0.04 0.1±0.01 0.1 ±0.01 0.1 ±0.001 0.03±0.001 N. neothecis 0.008±0.0005 0.9±0.01 0.1±0.0003 0.1±0.01 0.1±0.002 0.03±0.001 Oxyopes sp." 0.007±0.004 0.8±0.02 0.1*0.03 0.1 ±0.04 0.09±0.001 0.02±0.001

1. DBM = Plutella xylostella; CL=Trichoptusia m; AW - Spodoptera tatifascia; P •-Pilemiaperiusal= Unidentified noctuid. 2. All spiders were fed on the last two instars of host larvae exccpt those with • (five species) which could consume only the first two instars.

294 Table 5: Relationship between spider weight and weight of food consumed.

Species Spider's weight (g) Food consumed(g/g spider wt.)

P. viridens 0.30 0.42 L.fusca 0.15 0.82 A. argentata 0.11 0.54 L. atlantica 0.10 1.37 A. trifasciata 0.03 1.93 Habronathus sp. 0.01 3.60 Oxyopes sp. 0.007 1.00 Hentzia sp. 0.004 7.CO T. gonygaster 0.004 2.00

Spider weight is related to the inverse of the food consumption by the following equation. l/food = 0.437 + 6.553 (SE= 0.394 1.404)

Table 6: Effect of insecticide sprays on the population of spiders and cabbage pests

Population mean ± SE Species Unsprayed Sclecron Pegasus Basudin

Predators L. atlantica 8.62 ± 2.44 1.52* ±0.69 0.89* ±0.55 1.72 ± 2.01 L.fusca 7.56 ± 1.70 1.89* ±0.75 1.51* ± 0.75 0.001 ±0.03 T. gonysaster 7.33 ±0.90 2.10* ±0.63 1.16 ±0.70 3.33 ± 1.82 H. vittata 2.66 ±0.54 0.47* ± 0.28 0.001 ±0.02 1.1.4 ±0.73 A. trifasciata 1.77 ±0.45 1.01 ±0.60 0.001 ± 0.005 0.59 ±0.45 Oxyopes sp. 1.26 ±0.42 0.42 ±0.20 0.14 ±0.12 0.05 ±0.06 Habronathus sp. 0.69 ±0.37 0.23 ±0 14 0.08 ±0.08 0.02 ±0.04 Pests P. xylostella 3.1 ±0.37 4.3 ±0.58 7.4* ± 1.22 6.2* ± 1.11 T.ni 1.26 ±0.23 2.4* ± 0.43 2.8* ±0.75 2.0 ±0.63 S. latifascia 0.7 ±0.17 0.8 ± 0.24 1.4 ±0.53 0.6 ±0.35

* significantly (p < 0.05) different with the unsprayed plots.

REFERENCES

Alam, M M. 1992. Diamondback moth and its natural enemies in Jamaica and some other Caribbean Islands. Proceedings of the 2nd International Workshop on Diamondback moth and other Crucifer pests, AVRDC, Tainan, Taiwan, 233-243.

Anderson, J.F. 1978. Energy content of spider eggs. Oecologia 37: 41-57.

Greenstone, M.H. 1978. The numerical response to prey availability of Pardosa ramulosa (McCook)

295 (Arane-ae: Lycosidae) and its relationship to the role of spiders in the balance of nature. Symposia of the Zoological Society of London, 42: 183-193.

Greenstone, M.H. 1979. Spider feeding behavior optimizes dietary essential amino acid composition. Nature 282: 501-503.

Greenstone, M.H. 1980. Contiguous allotopy of Pardosa ramulosa and Pardosa luoba (Araneae: Lycosidae) in the San Francisco bay region, and its implications for patterns of resource partitioning in the . Amer. Midi. Nat. 104: 305-311.

Greenstone, M.H. Determinants of web spider species diversity: vegetation structural diversity vs. prey availability. Oecologia (Berlin) (1984) 62:299-304.

Greenstone, M.H., Morgan, C.E., Hultsch, A.L., Farrow, R.A. and J.E Dowse 1987. Ballooning spiders in Missouri, USA, and New South Wales, Australia: Family and mass distribution. J. Arachnol., 15:163-170.

Greenstone, M.H., Eaton, R.R. and Morgan, C.E. 1991. Sampling aerially dispersing arthropods: A high-volume, inexpensive, automobile and aircraft-borne system. J. Eco. ent. 84 (6), 1717- 1724.

Greenstone, M.H. and Bennett A.F. 1980. Foraging strategy and metabolic rate in spiders. Ecol. 61: 1255-1259.

Humphreys, W.F. 1977. Respiration studies on Geolycosa godeffrayi (Araneae:Lycosidae) and their relationship to field estimates of metabolic heat loss. Comparative Biochemistry and Physiology 57A: 255-263.

Levi, H. W. and Levi, L R. 1990. Spiders and their kin. Golden press, New York. Western Publishing Company, Inc. Racine, Wisconsin, 160 pp.

MacArthur, R.H. 1969. Patterns of communities in the tropics. Biol. J. Linn. Soc. 1: 19-30.

MacArthur, R.H. and MacArthur, J. W. 1961, On bird species diversity. Biol. J. Linn. Soc. 1:19-30.

Muckenfuss, A.E., Shepard, B.M. and Ferrer, E.R. 1992. Natural mortality of diamondback moth in coastal South Carolina. In Talekar (ed.) Diamondback moth and other crucifer pests: Proceedings of the second International Workshop, AVRDC, Tainan, Taiwan, 27-36.

Pianka, E.R. 1966. Latitudinal gradients in species diversity: a review of concepts. Amer. Natur. 100:33-46.

296 Fig. 1: Weight (g) of host larvae eaten/day and 5-day moving average by Lycosa atlantica

Fig. 2: Weight (g) of host larvae eaten/day and 5-day moving average by Heteropoda venatoria

297 Fig. 3: Weight (g) of host alrave eaten/day and 5-day moving average by

Fig. 4: Weight (g) of host larvoe eaten/day and 5-day moving average by Lycosa fusca

298 Tig. 5: Weight (g) of host larvae eaten/day and 5-day moving average by Habronathus sp.

Fig. 6: Weight (g) of host larvae eater,/day and 5-day moving average by Hentzia sp. vittata?

299 Fig. 7: Population of different soecies of spiders in cabbage fields, one week ofter spraying with three insecticides

300