Natural Adult Food of Some Important Chrysopa Species (Planipennia: Chrysopidae)

Acta Phytopathologica et Entomologica Hungnricn 27 (1 -4), pp. 141-1 46 (1992)

A. Bozsik

Plant Protection Department, University of Agriculture, GOdtillB, P.O.BOX. 303. H-2103, Hungary

The hind-gut contents of 1,709 chrysoid adults, comprising 6 species were analysed in order to determine their natural food. As it was expected only substances of plant origin (grains of pollen, yeasts and reducing saccharides in form of crystalline bodies) were found in the gut of Chrysoperla carnea. The hind- gut content of the other glyco-pollinivorous species, Anisochrysa prasina was similar to that of Ch. cnrnea but remains of arthropods have been observed in it in considerable quantities. The proctodeum of the predaceous species (Chrysopaformosa, Chtysopa septenzpunctata, Chrysopa perla, Chrysopa viridana) contained not only animal matter, primarily remains of aphids but also the above mentioned plant substances in different quantities and proportion. Relying upon these findings it seems that Ch.septcnzpunctrzta and Ch. virid~lnamay feed on honeydew or other sweet sccrelions, wcrc they can pick up yeasts and saccharides, more often than Ch. perla and Ch. j'orntosa. Spores of fungi also occurred in small quantities bcsides unidentifiable ingested matlcr in all species examincd.

Literature generally divides into two groups the better known species according to their natural adult feeding habits. So there are carnivorous or predaceous species feeding on small, soft-bodied arthropods (mainly aphids), and the so called glyciphagous and pollinivorous species making use of pollen and sweet liquids: nectar of flowers, honeydew. We must note here that predaceous chrysopids can also feed on insect honeydew, flower nectar and various similar substances (Principi and Canard, 1984). These kinds of food were generalizated as alternative food for the carnivorous species with the remark that they enable longevity but does not the reproduction (Canard, 1973 unpublished in Principi and Canard, 1984). Ahnost all of these data are based mainly on observations in nature and results of laboratory rearings but only a few research work was done on the alimentary canal. We have attempted in this study to estimate the most frequent kinds of food of some chrysopid species with the method of analyses of gut contents in order to determine the proportion and quantity of their more important components.

Materials and Methods

Lacewing adults were collected for gut analyses weekly fro111 April-October, 1984 and 1985 in an uncultivated area and a backyard orchard in Giidiillii (30 km north-east of Budapest). Captures were obtained by sweeping net. The individuals were determined based on the descriptions Aspiick et al. (1980). Specimens were dissected as quickly as possible mainly immediately after the captures. The hind-gut was examined for relative fullness and diet composition. The abdomen was incised, the hind-gut was excised and placed into a drop of water on a carnea praslna forrnosa 7-puncta ta

n-72 nz4~

Fig. I. Food hahits oi Ihe adults ol some important chtysopid species (D=dominanl. L=large quantity, C=considcrahlc quantity, S=small quantity, V=vcry small quantity; P=pollcn, C=cryst;rllinc bodies, Y=yc;~sls,A=rcmain arthropods, O=othcr animal matter, S=sporcs and conidia, U=unidentifiahle ingested mattcr; n=no. of adults dissected)

microscopic slide. After opening the excised gut its content was dispersed, covered with a cover glass and 5 random fields were examined (magnified 100 times). The character- istic and recognizable p;lrticles were counted or their quantity was estimated. After the counting the gut contents were tested for reducing sugar by adding a drop of reagent (3.5 g copper sulph:ite dissolved in 25 ml dist. water, 15 g glycerine added then filled up to 100 ml v:,lurne with 15% sodium liycirnxide (Stapf, 1955 in: Ickert, 1968). After adding this reagent the slide wz1rmt.d over a spirit lamp till precipitating of the orange-red cupro oxide. The different p;trticles were determined based of the following authors' work: Brinhe~yiet al., 1985; Strak;~,1075.

Results and Discussion

Following is an explanation of the graphic data (Fig. 1). Bars nbove the X-axis for each species express the quantities of each indicated dietary component. Bars below the X-axis express the relative freq~lencyof dietary cclmponents. Numbers within the bars indicate the percentage of the occurrence of the indicated component in the gut. Table 1 represents the c;itegories of estimation on the quantity of the gut ct~mponents. Bozsikc Adult food of some in~porfanlChrysopa spec~cs

Quantitative categories of estimation of the gut components

Gut components Quantity estimated Crystalline bodies, remains of Pollen grains, Cells of art hropods, unidentifiable spores, conidia yeast ingcstcd matter No. No. Dominant over 50 - - Large quantity 20-50 over 500 - Considerable quantity 5 -20 50-500 over 500 Small quantity 1-5 10-50 100-500

Very small quantity 0.1-1 -- 1-10 10-100 a = The occurrcncc of compounds estimated in 5 microscopic fields related to the averagely iilled hind-gut contcnt.

This species is regarded to feed sweet secretions and pollen but some study sug- gested to be an aphid eater (Bansch 1964, Tauber and Tauber 1986). On the basis of 1283 dissections our study confirmed only the first statement, revealing a diet high in pollen and crystalline bodies with considerable quantities of yeasts. These components were relatively frequent in the hind-gut. Other animal matter (lepidopterous scales) also have been observed in very little quantities and frequency.

Its food habit was characterised as glyciphagous and pollinivorous by Ickert (1968) and Principi and Canard (1984). Principi (1958, in Principi and Canard, 1984) observed remains of pollens in its excrement and alimentary canal. Gut contents of 32 individuals indicated they were really mainly glyco-pollinivc>rous feeding on polle11, yeasts and sweet solutions but remains of arthropods (aphids) have been found in considerable quantities and relatively high frequency in their hind-gut (Fig. 1).

Clirysopa formosa Brauer

Principi and Canard (1984) characterised Ch. formosu as carnivorous species feeding primarily on aphitls with the remark that by keeping it on water and honey it survives a long time, but does not breed. Other authors reported that honey (Park and Woo, 1986) and brewer's yeast hydrolisates (Shuvakhina, 1971) as diet components gave moderate results for Ch. ,formosu. Relying upon 231 gut contents animal matter (aphids) predominated as diet, but other items such as pollen, crystalline bodies and yeasts occurred in considerable and

Acrn IJ/lyloyolhologicn rl Ento~nologicirIltingirrlcn 27, 19g2 small quantities. Their frequency was medium except that of the yeasts, which was quite low. (Fig. 1).

A carnivorous diet was indicated by Principi and Canard (1984) for this species. Our data (on the basis of 72 dissections) substantiated this, founding arthropod remains (aphid) in large quantities and frequency, yet crystalline bodies in high quantities, pollen and yeasts in considerable quantities were displayed with medium frequency (Fig. 1).

This species is regarded as predominantly predaceous (Principi and Canard, 1984) However, Canard (1973, unpublished in Principi and Canard, 1984) observed also grains of pollen and spores of fungi, besides remains of aphids in the gut of CII. perla . In our study 44 hind-gut contents were examined. Remains of arthropods (chiefly aphids) were the dominant items, beside pollen, crystalline bodies and yeasts were observed in considerable and small quantities. Pollen and crystalline bodies were quite frequent but the occurrence of yeasts was low (Fig. 1).

CIi. viridutlu 21s an other of the genus Cl~tysoj~uhas been ch;~ractcrisedas carnivorous (Principi and Canard, 1984). 47 individuals were dissected and animal matter (remains of arthropods, predominantly aphids) were found in great amounts and in a high frequency. Foods of plant origin such as pollens, yeasts and crystalline bodies occurred in considerable quantities and in medium or high frequency in the hind-gut (Fig. I). Lacewings feed often of pollen perhaps because it is rich in protein and contains also fats, carbohydrates and vitamins. As mentioned above some authors found pollen remains not only in glyco-pollinivorous species (Principi, 1940, in Principi and Canard, 1984) but also in CII.perh (Canard, 1973, unpublished in Principi and Canard, 1984). We observed pollen grains in the gut of all species in at least considerable quantities and their occurrence seemed not to be occasional. If we note that several predaceous species have been observed on flowers (Killington, 1937, in Principi and Canard, 1984) and the fact that the addition of pollen to the diet increased the longevity and retained the reproduc- tive potential of CIi. perla females (Canard, 1973, unpublished in Principi and Canard, 1984) pollen seems to be a valuable food also for carnivorous chrysopids. The following component of plant origin was represented by crystalline bodies. By testing with the reagent cited above about 10% of the crystalls turned to red. These crystalls may be reducing mono- and/or disaccharides and the unchanged ones not reducing saccharide derivates. Also Ickert (1968) observed that CII. curllea adults fed only on sucrose solution during 3 months gave up an excrement of black, crystalline form. The Bozsik: Adull food of some in~portanlChlrysopa species 145 same author could also detect glucose in the crop of the same species based on the method cited here. This kind of food must have been taken by lacewing adults feeding on nectar, honeydew or other sweet secretions. Yeasts are used in almost every artificial diet for non- predaceous adult chrysopids (Hagen and Tassan, 1970; Principi and Canard, 1984), and they are very common in nature (do Carmo Sousa, 1969). Yeasts. because of their frequency and high protein content, are important as food for some insects such as Curculionidae, Ceramhycidae and some Etzehrio spp. (do Carmo Sousa, 1969). That is why their occurrence in the proctodeum is not surprising. Hagen et al. (1970) reported that yeast symbionts occur in C/z. cartzea and in many glyco-pollinivc>rous species. These authors assume yeasts could provide the essential amino acid valine absent in pollens and honeydews. Ickert (1968) admits the presence of yeasts in the chrysopids' alimentary canal but consider them as "P;lssanten" and not as symbionts. In our study vegetative yeast cells cxcurred in the hind-gut contents of all species examined but the gut of predaceous species contained them less and more rarely than of glyco- pollinivorous lacewings. Our data substantiated only the presence of yeasts in the gut but conclusions about their role as syrnbionts cannot be drawn. These components may be either symbiclnts or the above mentioned "Passanten" or simply foods. Animal matter was evidently either dominant or abundant in the carnivorous species but surprisingly it was found in A. pra.~irluin considerable quantities. It is possible that these parts were glued in sweet liquids in nature and the adults of A. prasitza have taken them by feeding an honeydew, or simply this species may have a tendency to feed ;IS "omnivore". The remains (fragnients, parts of arthropods) could not be identified because of their condition but fragments of aphid legs were recognisable amongst them. Further animal matter such as lepidopterous scales were found in seldom and very small quantities in the gut of several species. These particles were probably swallowed with honeyclew or other liquids. Similar observatio~iswere made by Killington (1937, in Principi and C:rn;lrd, 1984) in rel:~tic~nof A. ~vturulis. Spores and conidia occurred in small amounts but with a medium frequency in all species examined. Tliesc components might be glued in the honeydew and the lacewings must have taken them feeding on it. Indeterminable ingested matter was also observed in every species. It was found in considerable quantities and its frequency was at least medium or high. The results of this study suggest that the adult chrysopids may have greater food diversity in nature than it was reported formerly and the categories glyct-)-pollinivorous and predilceous are not wide enough to characterize exactly their feeding habits.

Acknowledgement

We thank Dr. L. Szalay-Marzsti for reviewing the manuscript. Literature

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Reference Citation: Bozsik, A. 1992 [1992.??.??]. Natural adult food of some important Chrysopa species (Planipennia: Chrysopidae). Acta Phytopathologica et Entomologica Hungarica 27:141- 146.

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