Dear Colleague,

this strongly depends on species (genus). Broods of some species are different, some ones not. It also depends if some of broods are overwintering (temperate zone) and/or some of them have continuous development (in some tropical areas).

How do you observe/collect the specimens?

I guess - if you have light trap (pheromone trap for some species), this may help you identify the peaks in number of captured individuals - ale approximately estimate the beginning and the end of generation... However, this is only indication.

Dood luck

Dear Colleague,

I  agree with Turcani, and I can add some notes. Do you need to monitor specifically adults of one species (one genus)? If the specific sex pheromone for males (e.g. for some Noctuidae, Pyralidae, ...) is available, you can use pheromone traps (which obviously capture only males). Otherwise, you can use light traps (which capture males and females). For the specific or generic identification, it will be necessary, often, to preparate and to study genitalia of the collected specimens, because the preservation of other useful characters  (wings, colours, and so on) is often very bad in moths by using traps. On the basis of the data obtained (e.g. number of specimens / week), you can try to recognize, by the number and the distribution of seasonal peaks in the captures, the different 'flights' indicating different annual generations. But, particularly if the number of generations by one species in one year is high, the 'flights' can be overlapping and it could be difficult recognizing peaks in order to distinguish generations. In various moth species damaging crops, the different annual generations in larval stage attack different parts of the plant, so the monitoring activity can also be made by observing the different type of larval damage related to the phenology of the botanic species.

I hope I provided some useful considerations.

Best regards,

Rinaldo Nicoli Aldini 

I have been assessing the naturally occurring phenologies of thousands of Lepidoptera species for over 45 years in the state of Louisiana, USA.   Through this research, I have proven that most all of the statement previous published by any and all authors over the past two centuries concerning the number of broods of North American Lepidoptera are bogus and incorrect. Previous authors simply copied and plagiarized what previous authors stated in their publications going back to the middle 1800's

Many of my investigations have been published (310 to date), either individually by species, or sometimes by genera, or by entire families. example of one of them is attached.  I accomplished this feat by designing, fabricating, and operating around 400 different insect traps since 1969.  Light traps, flight traps, pan traps, pitfall traps, pheromone traps, etc., and documenting and analyzing adults captured in the field every single 24-hour period of every single day of every year for 45 years.

Some of my 310 publications illustrating these phenology assessments can be accessed freely at these two links:  https://independent.academia.edu/VernonAntoineBrouJr   and  http://www.lsuinsects.org/people/vernonbrou/index.html

An offshoot of this work has been the discovery of around 400 species of Lepidoptera new to science within Louisiana.

Thanks vernon. I monitored butterfly form its emergence to disappearance. I am not considering the first emergence of butterfly  as first generation as most people consider it.i always consider this half because  other phonological stages( egg, larvae, pupae) were in previous year. i say first emergence of butterflies.

then every peak i consider a generation in current year through general time series method. In addition  i kept the culture growing in iron shade nets  to see what i am observing in field is   same. as i am monitoring in iron net house. seems me quite ok.

Very useful indications and considerations by a colleague (Vernon) who has much more experience than I have,

Rinaldo Nicoli

I would like to add that, as the number of annual generations of some species varies in dependence of geographic area, latitude, altitude and other factors,  the data provided by previous and ancient authors must be considered  and evaluated with reference to the different conditions in which the same were obtained,

Rinaldo Nicoli

We have monitored Noctuids during 9 consecutive years associated to tomato and corn  fields in Southern Portugal. We have used sex pheromone traps and blacklight traps (always 2 per field distant of at least 50m). We found pheromone traps useful for first and last single individuals, but the light traps more reliable during peak activity , for a simple reason: We are not the only ones being interested in Noctuid capturing. There are owls, Strix and bats all over the fields. They learn and visit the food attracting trap field parts, capturing the insects in flight so that we don't get the full picture, at least with pheromone traps (mono-specific). Many pheromone researchers thought and published that the pheromones during peak populations were less attractive than the females, but they wouldn't go to the fields at night. If these pheromones function in other moments, it's not their quality, but ecology which interferes. Using the light traps, we have much more work for sorting out, but the predators are not species specific, and the picture we obtain is more reliable. To distinguish between local and migrating populations you need to know the attractive plant organ for the specific pest (for H. armigera, it is the open flowers, more than 8 per plant)). Comparing sampling of developmental stages in the field and the adults from the traps you can distinguish between invasions and local population, but only in gross terms. We once had more than 450 H. armigera in a trap in one night, comparing with a maximum of some dozens, normally. It was a weather frent (thunderstorm) which "washed down" migrating insects. Hope these observations might be helpful.

Dear Colleague:

It is convenient to work on insect systems that are univoltine.  Then the problem of generations is a non-issue.   But working on a univoltine, sometimes bi-voltine moth (genus Orgyia, Family: Erebidae) sheds some light on egg hatch and generation time.  These moths lay their eggs in a single egg mass on the cocoon from which the female eclosed, the eggs over winter and hatch in spring.   By recording daily hatch, I have detected a delayed hatch that may last up to three weeks in sibling hatch time.  So siblings may be up to 3 weeks different in their development and all from a single female.  Think what this does to the generation time and how this would compound in a multi-voltine species.  This would all help to cloud generation times or moth flights and one's effort to identify generations.    I propose that this system benefits the moths by reducing the probability of sibling matings.  May I suggest that you take into account the egg hatch pattern in any system where you are trying to determine generations as this is the critical start of any and all generations..  

Schaefer, I monitored the moths and white butterfly( line transect). where light and  pheromone traps do not have any role in butterfly monitoring. yes i second your statement that  egg hatch is delayed. there is different  heats unit accumulation in one generation and another generation. i observed it  in field. I raised culture of whites in iron mesh net house in filed. After complete emergence of one generation, egg to adult. when adult lays eggs and  then i shifted these adults  to another compartment to observe their  longevity.This i way i do for all generations. So DD mechanism is changing from one gen to another gen.Even egg hatch varies what i observe it at constant temp. in laboratory to see this mechanism.I came to conclusion that  heats units accumulated from egg to adult by different generations is a useful way for full generation.Larval feeding at different temperatures either increase or decrease their longevity.Sometimes food consumption is more at high temp in field conditions and in lab it is totally different which i see but not work on that.Thanks all for my question 

Pheromone traps.

  Mukherjee @@@@These pheromones will not work here but  i need your address for  future procurement. @@@@@.

Here are images of some of the traps I have used over the past 46 years.  

https://www.academia.edu/9665262/Images_of_some_of_the_insect_traps_designed_fabricated_and_operated_by

Here is another example, one of more than 300+ similar publications illustrating how I have been monitoring and documenting via publications the number of annual broods of moth specimens. This publication illustrates five species of the moth genus Argyrostrotis occurring in my state of Louisiana, USA. To obtain such a great amount of data points requires documentation daily for many years, even decades of data to be able to correctly analyze a true naturally occurring picture of the annual broods of a species.  This same method can be used for any insect orders.  This is an accurate and true picture of annual broods, not a statistical estimation or shortcut method of guestimation of such, as every moth of each species has been individually added to the database.