99 T A N E (1967) 1 3 : 9 9 - 105

S T U D I E S O F E P H E M E R O P T E R A IN T H E

A U C K L A N D A R E A

by J . A . M c L e a n *

I: L I G H T T R A P P I N G IN C A S C A D E K A U R I P A R K

I N T R O D U C T I O N

There i s no record i n the ava i lab le l i terature at present of any attempt to obtain mayfly imagos and subimagos by means of l ight trapping. The fo l lowing data were recorded from the Waitakere Stream in the region of Cascade K a u r i Park during the period 26 October to 8 November 1966.

M E T H O D

A l ight trap was set up on a gravel bank jus t below the junc t i on of the Waitakere and Cascade streams. A 240 vol t , 125 watt mercury vapour bulb was run from a portable petrol-driven generator. T o provide a large white surface area, the bulb and holder were set i n the middle of an inverted h ike r ' s tent. T h i s proved very sat is factory as the large white surface ass i s t ed in easy capture of the mayf l ies . The l ight trap was run every evening from 6. 45 p. m. t i l l 9 p. m. No further spec i e s arr ived after this time and a fa ir ly representat ive catch of 100-200 ind i v i dua l s was taken during the t ime. Ident i f icat ion of spec ies was made from P h i l l i p s (1930) and Penn ike t (1966).

R E S U L T S

Da i l y captures varied accord ing to the weather. It was noted that by far the most mayfl ies were seen at dusk on days when i t was overcast and s t i l l wi th l ight misty ra in . The low- f ly ing spec i e s such as Zephlebia cruentata and Atalophlebia nodularis cou ld be caught readi ly by hand net but higher f l y ing spec i es such as Coloburiscus humeralis and Rallidens mcfarlani were sampled only by attract ion to the l ight trap. No net co l l e c t i ons have been inc luded in the resu l ts .

The t o ta l number of mayf l ies sampled over the 14 days was 1, 554. For an ana l y s i s of the populat ion present see Tab l e 1. T h i s shows that * D e p a r t m e n t o f Z o o l o g y , U n i v e r s i t y o f A u c k l a n d

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the most abundant spec i e s were Coloburiscus humeralis, Deleatidium fumosum and Zephlebia cruentata.

E a c h spec i e s had four d i s t i n c t groupings; these were male and female subimagos and imagos . Ove ra l l i t can be seen ( F i g . l ) that far more subimagos (66. 5%) than imagos (33. 5%) were captured. The proportions for a l l sp e c i e s are summarised i n F igure 1 whi l e an a n a l y s i s of each spec i e s i s shown in figure 2.

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o 3 0 " —

c —

. U •* 20-

. . . + + —

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F I G U R E 1

— Male s u b i m a g o

Male i m a g o

Tab le 1 - Popu la t i on A n a l y s i s

Spec ies Number in sample % of to ta l

Coloburiscus humeralis 511 34. 3 Deleatidium fumosum 406 26. 2 Zephlebia cruentata 228 13. 6 Atalophlebia nodularis 117 7. 5 Zephlebia versicolor 106 6. 8 Rallidens mcfarlani 77 4. 5 Ameletopsis perscitus 45 2. 9 Deleatidium cerinum 25 1. 6 Nesameletus ornatus 20 1. 3 Zephlebia dentata 16 1. 0 Deleatidium vernale 5 0. 3

To ta l 1556 100. 0

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F I G U R E 2

D I S C U S S I O N

It would appear that subimagos are more attracted to the l ight than the iraagos, even though more imagos were seen in f l i ght . F i gure 1 shows that nearly equal proportions of male and female subimagos were attracted to the l i ght . The deta i l ed ana l y s i s of each spec i es as i n figure 2 shows that i n 4 spec i es nearly 50% of a l l adults caught were female subimagos. These 4 spec i es were Deleatidium fumosum, Zephlebia versicolor, Ameletopsis perscitus and Zephlebia dentata.

In the most abundant spec i e s , Coloburiscus humeralis, the proportion of both female subimagos and male subimagos was 30%.

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Fewer male imagos were attracted to the l ight than any other winged stage even though swarms of Zephlebia cruentata and Deleatidium fumosum males were observed in the area of the l ight trap late in the afternoons.

Some spec i es of mayf l ies , commonly found in the Waitakere stream in l a r va l s tages , were not co l l e c t ed with the l ight . Two such spec i e s were Oniscigaster wakefieldi and Ichthybotus hudsoni.

During the 14 days of observat ion, some 11 spec i e s of mayf l i es were captured at the l ight trap.

R E F E R E N C E S

Penn ike t J . G . , 1966: Notes on New Zea land Ephemeroptera: IV A New Siphlonur id Subfamily: Ra l l i d en t inae . Records Canterbury Museum. 8 (3): 163-175.

P h i l l i p s J . S., 1930: A R e v i s i o n of New Zea land Ephemeroptera. Trans N. Z. Inst, 61: 271-390.

II: O B S E R V A T I O N S ON F L I G H T A C T I V I T Y IN T H E

W A I T A K E R E S T R E A M

I N T R O D U C T I O N

Mayf l ies are amongst the more graceful insec ts and the danc ing swarms of adults have been mentioned often i n the l i terature , (see Needham, Traver and H s u , 1935). Recorded observat ions on New Z e a l a n d spec i es are few and those recorded here supplement ex i s t ing data . Dur ing a 14 day f i e ld tr ip to the Cascade Kaur i Park area of the Waitakere Stream, from the 26th October to the 6th November 1966, severa l spec i es of mayf l ies were observed. T h i s i s an account of f l ight ac t i v i t i e s seen during th is period.

M E T H O D S

Ident i f icat ion was effected after capturing males from danc ing swarms us ing a long-handled net. The net was 70 cm long and had an

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aperture 40cm i n diameter. The handle of the net was 1. 5 metres long with four extens ions of 1 metre so that the greatest height that cou ld be sampled was 5. 5 metres. The net was made of f ine terylene which was l i ght enough not to damage the imagos.

R E S U L T S

The subimago that emerges from the f ina l l a r va l instar i s a d u l l -winged f ly which after a vary ing length of time f l i es into the protect ive cover of the vegetat ion bordering the stream and i s not seen again un t i l transformed into the c lear-winged imago. In the evening imagos of many spec i es of mayfly were seen on the wing above the Waitakere Stream. The behaviour of the danc ing swarms of male imagos and the o v ipos i t i ona l behaviour of the female imago var ies from spec i es to spec i e s and observa­t ions have been recorded for i nd i v i dua l spec i e s .

1. Coloburiscus humeralis: -

Female imagos of th is spec i es were captured at dusk as they flew up from vegetation near the stream towards the males which swarmed over ri f f les at heights from 10-20 metres. Capture of these male imagos was imposs ib le by net but many were recorded us ing l ight trapping techniques (see part 1 of this ar t i c le ) .

The male imagos were observed to f ly s l ow ly upstream r i s i n g and fa l l ing as they went and after progressing about 60 metres they darted swi f t l y downstream to approximately the point where they had begun their dance and started again. Females were observed to leave the vegeta­tion at the s ide of the stream and j o in the dancing swarms of ma les . The nupt ia l dance of th is spec i es has been recorded by Wisely (1965). Some female imagos that came to rest short ly after copulat ion were seen to be carry ing a large orange egg mass under their hooked abdomens. After rest ing for a wh i l e one of the female imagos took to the wing and was seen to ov ipos i t i n a nearby r i f f le . An egg mass was detached from a female imago and p laced in a beaker of water. The egg mass set t led qu ick ly to the bottom and remained intact . Presumably the ov ipos i t ed egg mass wedges between stones i n the r i f f l es . It i s worthy of note that larvae of this spec ies are found only i n r i f f l es .

During a wet afternoon the author crossed a road near the stream and observed a group of male imagos hovering over a d i t ch at the s ide of the road. The torrent of water f lowing down the d i tch probably acted as a st imulus for the male imago to swarm. The height of th is swarm was

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only 2-6 metres and after the rain ceased they d ispersed.

2. Zephlebia cruentata:

The subimago of th is spec ies i s orange-red in cc±our and i s perhaps one of the more d i s t inc t i v e mayf l ies that are found i n the Waitakere Stream. It i s r i va l l ed only by the bright ye l l ow subimago of Ameletopsis perscitus.

At 3. 30 p. m. on Saturday 5th November, th is spec i e s was noted to be swarming throughout the whole length of the Waitakere Stream that was under observat ion — a fu l l 500 metres of stream bed. The weather was overcast and s t i l l w i th a l ight misty ra in f a l l i ng . The height of the swarms was 0-3 metres and they were more abundant over the quieter poo l areas of the stream. T h i s spec i e s has cauda l f i laments approximately twice as l ong as the body and the males t ra i l ed these f i laments in their graceful f l ight .

O v i p o s i t i n g females were observed at the s ide of the poo ls . Here they rose and f e l l about 2 metres. At the surface of the water, the female touched her abdomen on the surface f i lm presumably washing off a few eggs each time. The t i pp ing of her abdomen on the surface f i lm could be seen because of the r ipple pattern she created at every d ip . Swarms of Zephlebia cruentata were seen most frequently i n overcast dr i z z l e cond i t i ons .

3. Atalophlebia nodularis:

Above the dancing swarms of Zephlebia cruentata this smal ler spec i es of mayfly could be observed at a height of 5-10 metres. The lower l e ve l s of the swarm were sampled by means of the long-handled co l l e c t ing net. These danc ing swarms congregated mostly above poo ls .

4. Rallidens mcfarlani:

Females of this spec i es were captured as they flew up from the vegetat ion at the s ide of the stream at dusk. Mat ing was not observed but a female imago was seen ov ipos i t ing . On a quiet pool s ec t i on of the stream the female imago made repeated low f l ights over the surface of the water, l e a v ing a t ra i l of surface disturbance. Many such f l ights were made ac ross the pool and after a short time the female imago had c r i s s ­c rossed the whole area. It i s worthy of note that larvae of this spec i e s are found most abundantly i n areas such as these.

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DISCUSSION

Macan (1963) says of Ephemeroptera ov ipos i t i on behaviour that " s o m e appear to se l ec t a s i t e to lay their eggs, but others lay them i n a haphazard way and many nymphs must d i e in . unsui tab le p l a c e s " .

These recorded observat ions seem to ind ica te def inite preference of ov ipos i t i on s i te by the female imago of the above spec i e s , coupled with a def inite corre lat ion between ov ipos i t i on regions and areas of h ighest l a r va l densi ty .

R E F E R E N C E S

Macan-T . T . (1963)_Freshwater Eco logy . Longmans.

Needham, Traver , H s u . (1935) " T h e B io l ogy of M a y f l i e s " I thaca N . Y .

Wisely B . (1965) s tud ies on Ephemeroptera. HI Coloburiscus humeralis (Walker}; Morphology and Anatomy of the Winged Stages. N. Z. Journ. Sci. 8 (3) pp. 398-415.