Plant Protection Department, Faculty of Agricultwe, Cairo University, United Arab Republic

Biological Studies on the Soil-Inhabiting Bdellid Mite, Spinibdella biftrrcata (Acarina: Bdellidae) in U.A.R.

By 2. R. SOLIMAN and M. I. MOHAMED

With 6 Figures

Abstract

The Bdellid mite Spinibdella bifurcata, was recovered all over the year from soil, litter, dry leaves and bird-nests. Its life cycle is composed of four moving and four quiescent stages. Five generations during the year were recorded. The propagation is a parthenogenetic one.

S. bifurcata is of predatory habit. Its food preference is mainly on the book-lice insects (Corrodentia). The individual mite in its whole immature stages consumed about 76 and 56 preys during spring and summer respectively. Canabalism was noticed.

Collecting and rearing methods as well as the development, oviposition, spinning, feed- ing, life-cycle, overwintering and behaviour of the mite species are described. A description of all stages is given.

Introduction

Biological investigation on members of the Bdellidae Duges, 1834 were initiated by WOMERSLEY (1 933) and CURRIE (1 934). Their significance in bio- logical control of the lucerne flea, Smynthurus viridis L. were stressed by SWAN (1940), MILLER (1947) and JENKINS and FORTE (1942). It was reported by JOHNSTON (1960), in Western Australia, that the major natural enemy of this insect was the predaceous bdellid mite, Biscirus lapidarius. Certain num- bers of the Bdellidae were found as predators on other mites. LORD (1949) recorded that Cyta latirostris Herm. attacked the active forms of Paratetra- nychus pilosus C. & F. BAKER and WHARTON (1 952) added that some species of Bdellu, of common occurrence in the citrus orchards of California, were predaceous on the Collembola insect, Smynthurus wiridis L.

A rather extensive research work on the biology of the predaceous mite, Bdella depressa Ewing was carried by SNETSINGER (1956). He stated that eggs of this mite was the most abundant overwintering stage. Other stages, except larvae, were capable of overwintering under the bark of trees. With reference to its predaceous habit he indicated that larvae, nymphs, and adults of this bdellid mite fed on all stages of the phyto hagous mites, Tetranychus telarius L., Petrobia latens Muller, Petrobia horti Ewing and So!iaotetranychus sp. It also attacked the collembola species, Bourletiella hortensis Fit& and Willowsia platani Nicolet.

The present study deals with the development and biology of Spinibdelfa bifurcata, which is a dominant Bdellid mite in the soils of U.A.R.

2. ang. Ent. 70 (1972), 15-23 @ 1972 Verlag Paul Parey, Hamburg und Berlin

16 %. R. Solirnan and M. I. Mohamed

Materials and Methods

Collection of mites

Adults of Syinibdella biftrrcata as well as the book-lice insects (Order: Corrodentia) were collected from their terrestrial habitat e.g. soil, litter, organic manures and bird’s nests by a modified TULLGREN 1913 (Berlese) method. A zinc metal funnel of 33 cm deep u id 18 c m iii;uneter was used. A four mesh sieve was fixed at about three ccn:imeters blew the funnel rim. A wooden box with a 60 W lamp was invcrted on the funnel. Distance from lamp t o the sieve was 10 cm. The sample was placed on the sieve, covered with the wooden box and the lamp was switched on to provide heat. A 10 cm diameter petri dish filled with 50 ml water, was placed beneath the end stem of the funnel to receive extracted animals. Six of such modificd Berlese funncls were employed in this study.

After 24 hr contents of the petri dish were examined and the specimens were removed by n small needle. The were placed on a filter paper for dryness.

Specimens identification

Adults and immature stages of mites were mounted on glass slides in Hoyer’s medium (50 ml distilled water, 30 gm gum arabic, 200 gm chloral hydrate and 20 ml glycerin). After placing the cover slips, slides were gently heated until bubbles appeared. This technique allowed for stretching and clearing of the specimens. Slides were labelled with the locality and date of mounting. Microscopical examination and Camera-Lucida drawings were used for identification. Diagnosis of specimens were carried after refering to the taxonomic guide of ATYEO (1960).

Rearing procedure

A glass ring of nine millimeters diameter and 10 mm deep was fixed by paraffin wax on a glass slide. Bottom of the re- sultant chamber was covered with a thin layer of soil which kept moistured with the aid of a wet drawing brush. Adult females of S. bifurcata were placed in such prepared rings. A glass slide was placed over the ring and fastened with rubber bands (Fig. 1).

Females were left in these chambers tc deposit eggs and transferred daily to new rings for the estimation of fecundity and incubation periods. Newly hatched larvae were put singly in rearing rings. Each was supplied with known numbers of book- lice insects at its food source. They were leff in these rearing chambers till matu- rity.

The rearing rings were stereomicros- copically examined twice daily at 8.0 a.m and 8.0 p.m throughout the seasons. Fig. 1. The rearing ring

Results

I . Oviposition and hatching

Adult females of S. bifurcata required a pre-oviposition period. This period was determined by the prevailing temperature (Table 1). It is evident that

Biological Studies on t h e Soil-Inhabiting Bdellid Mi te , in U.A.K. 17

with the increase in temperature the period of pre-oviposition decreased. This temperature factor was noticeable during months of the winter season when average temperature was relatively low.

Table 1

Average pre-oviposition periods during seasons

Spring Summer Autumn Winter

27.8 28.1 27.4 19.7

5 4 6

113

The female usually preferred to deposit its eggs in groups under a spinning web. Single scattered eggs, however, were noticed in the ring. Number of eggs per web ranged from 8-21. Female stayed without feeding inside their web for three to five days for guarding its eggs. No oviposition took place during winter. Newly deposit eggs were usually creamy white in colour, then changed gradually to light orange after an elapsed time depending on temperature. It varied from three to five days at 28.5’ C to 10-13 days at

Table 2

Incubation periods of S. 6ifHrcuta eggs as affected by temperature

Season Aver. Temperature PC)

Incubation Period (days)

Spring Summer Autumn Winter

22.1 28.7 27.4 26.3

16.0 7.0 8 .O

10.0 I

22.4’ C. This changing colour first appeared in one side then spread all over the egg. An incubation period prior the deutovum stage was noted. Prevail- ing temperatures during the different seasons affected such incubation period (Table 2).

Prolonged incubation was correlated with decreased temperature. Eggs entered into the deutovum stage stayed for three to four days at 25.5 f 3’ C then hatched. Hatching occured through a slit a t the side where the embryo was laying. Larva, yellow in colour and with three pairs of legs, crawled out leaving behind a transparent egg shell. Upon emergence it moved actively in search of food.

2. Postlarval developments

After feeding larvae entered into a quiescent stage during which they ceased both feeding and movement. Protonymphs, with four pairs of legs, then emerged, fed and entered into a quiescent stage then deutonymphs emerged. Upon reaching their full growth they passed through quiescent stage and tritonymphs emerged. These tritonymphs fed, and entered into a quiescent

18 Z . R. Soliman and M. 1. Mohamed

stage after which adults finally appeared. Here again the duration of the immature stages changed according to seasons (Table 3).

Table 3

Average active movement and quiescence periods for the different immature stages during seasons

Movement and quiesceiit periods (days) Season Larva Protonymph Deuronymph Tritonymph

M. Q. M. Q. M. Q. M. Q.

Spring 1 1 4 8 3 6 3 6 3 Summer 5 2 3 2 3 2 4 3 Autumn 5 2 4 2 4 2 8 3 Winter 9 3 13 5 15 6 106 7 M & Q = moving and quiescent stages, respectively.

It can be seen that this mite passed during its post larval development through four active and four quiescent stages. Times of active movement and quiescence depend, however, on seasons (Table 3). Data indicate that the larval, protonymphal and deutonymphal periods ranged from 2 to 15 days. Only the tritonymphal moving stage ranged from 4 to 106 days, with a quiescent period of 3 to 7 days. From the preceding observations it can be stated that any moving immature stage of S. bifurcata, when fully grown and before changing to the subsequent stage, entered into a quiescent stage during which the mite stopped movement and feeding. It stayed in such quiescence either beneath its webbing or on the soil surface. During quies- cence the larva was observed stretching its mouth parts and first pair of legs anteriorly while the second pair of legs laterally and the third pair posteri- orly. Protonymph, deutonymph and tritonymph stretched their fore legs and rostrum anteriorly and their hind legs posteriorly.

In moulting the old integument splitted transversely between propodo- soma and hysterosoma. The mite got rid of its old skin through a twisting movement. This was followed by a drawal of its front legs and anterior part of the body outside. Finally, it crawled fowardly trying to escape from the posterior part of the exuvia. Colour of newly emerged individuals was usually light orange. ARer feeding it changed gradually to its normal colour which largely depended on food type.

Reproduction of S . bifurcata was characterized by the fact that eggs usually gave rise to females during all successive generations. This type of reproduction may be termed constant parthenogenesis.

3. Generations and Overwintering

Period and number of generations are subject to change by environmental conditions. In the present study temperature was found to affect the gen- eration period. Data as shown in table 4 indicate that the shortest period, 44 days, was noted during summer when temperature averaged about 28.7' C. Under the conditions of room temperature five generations per year were recorded, of which two took place in Summer and one per each of the other seasons.

Biological Studies on the Soil-inhabiting Bdellid Mite, in U.A.R. 19

Both newly emerged females and tritonymphs overwintered for a period of about 115 days at an average temperature of 19.3’ C. During this period

Table 4

Effect of temperature on a generation period

I Aver. Temperature Aver. Generation Period (“C) (days) Season I

Spring Summer Autumn Winter

22.1 28.7 27.4 19.9

70 44 49

214

they stopped feeding. The newly emerged females passed this period inside the web and without oviposition, while tritonymphs passed it under the web and as active moving stages.

4 . Spinning and Webbing

Individuals of S. bifurcata were capable of spinning webs during their life cycle. They used only their chelicerae for the manipulation of the secretions into very fine white thread-like structures. Upon exposure to outer atmos- phere they became rigged. The individual soon spread the threads between the soil granules or beside the border of the ring chamber in a half circle shape. The individual then laid down on its back to fur- nish the web cover which fi- nally took a net shap.

Temperature had a great effect on the spinning period. An increase in temperature caused a reduction in the spinning period. In winter, such spinning period ranged from three to four days while in summer it decreased to almost one day.

Rate of spinning increased with further development of the immature stages. It was found in the rate of 29.3 O / o , 66 O / o , 80.6 O / o and 85.1 O / o with larva, proto- nymph, deutonymph and tritonymph, respectively. Webbing furnished im- portant purposed the life span of this mite. Tritonymphs and young fe- males used it for overwintering. Adult females used it for oviposition and some immature stages passed their quiescence in them (Fig. 2).

Fig. 2. Quiescent stage of an immature stage of S. bifurcutu under a web

5. Description of Stages Egg

(Fig. 3) occurrence through a terminal lateral silt in the egg shell. Elliptical, with smooth surface and cream white colour. Deutovum

20 Z . R. Soliman and IM. I. Mohamed

Larva (Fig. 4)

Hypostome and chelicerae with two pairs of setae; the palpus attenuate with two long apical setae. Idiosonia with three pairs of legs, tarsus I11 with a very long seta (Trichoboth). Propodosoma with four pairs of setae, the

posterior sensillum very long and longer than the posterior, the lateral and me- dian of propodosomal setae of nearly equal length. Hysterosoma with seven pairs of setae.

Fig . 3. Deutovum of S. biftrvcata

Protonymph

Hypostome and chelicerae with two pairs of setae, the palpus with two apical setae, the external longer than the inter- nal. Idiosama with four pairs of legs, legs 111 & IV with a trichoboth, the pro- podosoma with two pairs of eyes and four pairs of setae, the anterior sensillum shorter than posterior. Hysterosoma with seven pairs of setae.

Deutonymph (Fig. 5)

Hypostome and chelicerae with two pairs of setae, the palpus with a pair of apical setae, the internal shorter than the external one. Propodosoma with two pairs of eyes. Ichiosoma with four pairs of legs, the propodosoma with the po- sterior sensillum longer than anterior one, the lateral propodosomal seta pre- sent and shorter than the medium pro- podosomal seta. Hysterosoma with seven pairs of setae, the internal and external humerals of equal length; the internal

and external humerals of equal length; the internal dorsal, internal lumbral and internal clunal also of equal length; internal and external sacral of nearly equal length; tarsus of leg I11 and tibia of leg IV with a trichoboth.

Fig. 4. view Of larval stage Of S. bifurcata

Tritony mph

Hypostome and chelicerae with two pairs of setae. Hypostome striated, the palpus with pair of apical seta, the internal shorter than the external. Propodosoma with two pairs of eyes. Idiosoma with four pairs of legs, the propodosoma with the posterior sensillum longer than the anterior one, the lateral propodosomal seta. Hysterosoma with seven pairs of setae; internal and external humerals of nearly equal length, internal dorsal, internal lumbral, internal sacral, external sacral and internal clunal of equal length. A pair of posterior anal setae present.

Biological Studies on the Soil-inhabiting BJellid Mite, in U.A.R. 21

Adult female (Fig. 6 )

Hypostome and chelicerae with two pairs of setae and with long stri- ations. Indiosoma with four pairs of legs, the propodosoma with two pairs of eyes and four pairs of setae; posterior sensillum longer than anterior one; lateral propodosomal seta present and shorter than median propodosomal

Fig. 5 . Dorsal view of deutonymphal stage of S. bifurcata

Fig . 6. Dorsal view of adult female of S. bifurcata

setae. Hysterosoma with seven pairs of setae, the internal humeral slightly longer than the external; the internal dorsal longer than the internal lumbral, the internal clunal shorter than the external sacral, the internal sacral long and of equal length ,with the internal humeral; pair of anal seta present. Tibia I and tarsus I11 and tarsus and tibia IV with a trichoboth.

6. Predaceous habits of S . bifurcata

In S. bifurcata, the book-lice insects (Corrodentia), were used as the main food source. The preys were offered twice daily at a rate of 10 individuals per predator larvae and growth stage. Data indicate that the individual predator in its whole immature stages consumed about 76 and 56 preys during spring and summer seasons, respectively. Although the number of consumed preys per the different immature stages was greater in spring than in summer yet the daily rate was smaller (Table 5). This could be explained on the basis of the quick development of the predator. Also, the more devel- oped the immature stages the more amount of preys are consumed.

-- 3 3 Z. R. Soliman and M. I . Mohamed

Table 5

Number of book-lice insects consumed by the immature different stages of S. biftlrcata during spring and summer seasons

Stage Number of consumed preys

Per \eason Per day Per sea\on Per d a \ Spr ing (23.50 C) Summer (28.0° C)

Larva 12 1 8 2 Protonymph 20 3 13 4 Deutonymph 20 3 16 5 Tritonymph 24 4 19 5

Predation was accomplished by the pushing of the predator chelicerae into the prey’s a t the head capsule between the eyes, or a t the region between the head and thorax. Absorption of body content was then took place. The predator fed on all stages of the prey, except eggs, and with preferance to small sized individuals. Certain observations were noted during the feeding process of the mite. The predator obtained its food either from one site on the prey or aRer three to five minutes feeding it changed to another site on the same prey. More than one predator could feed on the same prey. Where two predators attacked a prey it was noticed that one fed at a specific region between the head and thorax and the other on the posterior abdominal region of the same prey. Canabalism was noticed among individuals of S. bifurcata, since females were observed feeding on their larvae as well as larvae them- selves attacked each other.

Zusammenfassung

Zur Entwicklung und Biologie der Bodenmilbe Spinibdella bifurcata (Acarina: Bdellidae) in der U.A.R.

S . bifurcata wurde wahrend des ganzen Jahres in der Bodenstreu sowie in Vogelnestern gefunden. Ihr Lebenszyklus umfai3t 4 bewegliche und 4 ruhende Stadien. Fiinf Generationen im Jahr wurden beobachtet. Die Fortpflanzung ist parthenogenetisch.

S. bifurcata lebt rauberisch. Sie bevorzugt als Nahrung Staublause (Corrodentia). Eine einzelne Milbe verzehrte wahrend ihrer gesamten praimaginalen Entwidclung etwa 76 bzw. 56 Beutetiere wahrend des Friihjahrs bzw. Sommers. Kannibalismus wurde beobachtet.

Es werden die Sammlungs- und Zuchtmethodik sowie die Entwicklung, Eiablage, Spinn- tatigkeit, Ernahrung, Uberwinterung und das Verhalten der Milbe beschrieben. Auch wird eine Beschreibung aller Entwidclungsstadien gegeben.

References

ATYEO, W. T., 1960: A revision of the mite of familiy Bdellidae in North and central America. Kans. Univ. Bull. N. 8, 40, 343-349.

BAKER, E. W., and WHARTON, G. W., 1952: An Introduction to Acarology. Macmillan Company New York pp. 465.

CURRIE, G. A., 1934: The Bdellid mite, Biscirus lapidarius kramer predatory on the lucerne flea, Smynthrrrrrs airidis L. in Western Australia. J. Aust. Council Sci & Ind. Res. 7,

TENKINS. C. H.. and FORTE. P. N.. 1942: The lucerne flea. Smvnthurus viridis L. 1. D e n 9-20.

I . “ I

” Agric. W. Aust. 25, 116-120. ’

JOHNSTON, C. R., 1960: Biology and control of lucerne flea. J. Agric. Vict. Dep. Agric. 58. 505-515.

I ~~ ~~~

LORD, F. T., 1949: Mites and their predators. Canad. Ent. 81, 202-230. MILLER, L. W., 1947: The Biological control of insect pests in Tasmanica. Tam. J. Agric.

18, 117-119.

Biological Studies on the Soil-Inhabiting Bdellid Mite, in U.A.R. 23

SNETSINGER, R., 1956: Biology of Bdella depressa, a predaceous mite. J. Econ. Ent. 49,

SWAN, D. C. , 1940: The lucerne flea: its life history and control in South Australia. J. Dep.

WOMERSLEY, H., 1933: A preliminary account of the Bdellidae (Snout Mite) of Australia.

745-746.

Agric. S. Aust. 43, 462-471.

Trans. Roy. SOC. South Australia 57, 97-107.

Plant Protection Department, Faculty of Agriculture, Cairo University

Biology of the False Spider Mite TenzdpalpzjsppRnicae P. & B. in U. A. R. (Acarina - Tenuipalpidae)

By M. A. ZAHER and A. A. YOUSEF

With 3 Figures

Abstract

Biological aspects of T . pttnicae such as oviposition, hatching, moulting and life cycle were studied. Males were very rare and females reproduced parthenogenetically.

Temperature proved to be the important factor for development. The generation period changed from about 44.8 days a t average temperature 18.0' C in early spring to about 17.8 days a t average temperature 27.3' C in mid summer. Adult females which emerged in mid autumn hibernated during winter and began to lay eggs after a period of 122.5 days. On the other hand, relative humidity did not show any significant effect on generation period.

Throughout a whole year, ten generations were reared and of these about 9 generations occurred in spring and summer.

Introduction

False spider mites infest several horticultural crops, grasses and wild plants all over the world.

In U.A.R., members of the genera Brevipalpus, Cenopalpus and Tenui- palpus are the most important as they constitute major pests to various fruit trees (ZAHER and EL-BADRY 1964, RASMY 1966 and YOUSEF 1967).

To tackle such a problem, ecological and biological studies of these genera were carried out before carrying out any control program. ZAHER et al. (1969, 1970) studied the biology of Cenopalpus Zanceolatisetae (Attiah) and Brevipalpus phoenicis (Geijskes). Therefore to complete such investigations, it was found necessary to study the biology of Tenuipalpus punicael'ritchard & Baker, which severely attack pomegranate trees, for a whole year, under natural climatic conditions.

2. ang. Ent. 70 (1972), 23-29 @ 1972 Verlag Paul Parey, Hamburg und Berlin